Degreeing GT cams, I'm having issues(long, complicated)
09-27-2008, 02:28 AM
#1
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
Degreeing GT cams, I'm having issues(long, complicated)
Well, if you've taken off the cams on a 928, and put them back on, I need some help. If you've actually had the cams off a GT or Club Sport and put them back on that would be ideal.
Having perused WSM section 15-119 through 140-ish, covering the cam removal and assembly, I've gotten everything fine right up to the degreeing of the cam. In fact, I've got the 1-4 cam timed up nicely using the values in the book, with a slight modification. On the 5-8 set, I'm having issues.
We proceed through page 130 just fine. The tool lines up fine with 113mm between the casting ****, and the timing can be set grossly with the Porken tool. I've used the tool to set the pin for zero set with the crank at TDC. So far so good. The belt goes on, and now we are ready to double check the plunge setting with the dial indicator. Here's where things go bad.
l.Turn engine in direction of
rotation to TDC (cylinder No. 1 and 6. 90 degree cyl bank and using first throw for 1, and second crank throw for 6).
So we start with the crank on TDC, and the Porken tool hitting perfectly at the notch in the backing plate indicating a zero lash. At this point, we should set up the dial indicator to perform the plunge measurement.
2.In this position, the marks on
the camshaft gears and the flange
bearings must also be aligned.
True, I've just set that with the Porken tool and locked the pullys to the cams, with correct tension.
3.At the same time, check the marks
(older engines) or noses (newer
engines) on the camshafts.
Both marks point toward exhaust
side.
Yes.
4.Mount gauge with
cylinder head.
0 with 5 mm pretension hydraulic
tappet
intake valve.
Done(we are using inches, but we've set about 0.200" preload. As I do this, I notice on these cams that the lifter is already a bit on the opening ramp of the lobe, hmmmmmmm. This doesn't seem right at this point because the cam timing says that the cam(GT) opens at 3* AFTER TDC! My crank is on TDC, but the cam is already opening the 5-8 valve a bit.
II understand that these are hydraulic lifters so I wonder if there is a delay in valve opening due to the squish out of the oil in the lifter. But it doesn't seem like this is a common way to measure the delta of the valve opening. Anyway, we proceed.
Place gauge on hydraulic
cylinder 6 intake valve.
Cylinder bank 5 - 8
Specified value: 2.0 + 0.1 mm(this is the value for the S4, the GT specs are found later)
5.Turn the crankshaft on past
TDC (cylinder 1) while observing
gauge. Continue turning
engine until the lift is 1.6 +
0.1 mm. The 20" (after TDC,
cylinder 6) mark must now be
aligned with the index mark on
the drive belt cover.
This is where the train goes off the tracks. There is already some preload on the lifter. In fact, it's about 0.060" when crank is at TDC. So we start turning the crank bolt and by the time we move 0.122" plunge the crank indicates about 50* ATDC. It's supposed to be close to 20*, not 50*. Hmmm, strange.
So I go back to the way I've been degreeing cams since I was 13. I rotate the crank around so that the cam is on the heel. At this point, I prepare my plunge indicator, with no preload on the lifter like I had before. We've zero set while the lifter is on the heel, and now proceed to do the plunge. Guess what, as I rotate around I get ~0.122" right at 20* after TDC. Just like the book wants, except they prep the plunge reading at TDC. And, the specs say the cam won't open until 3* AFTER TDC! Neither of these sounds right.
Now, I go back to the Porken tool, because I'm in a quandary about the timing. We set it using that tool, and prepare to do another plunge test. Just like before, if we start at TDC and measure from there, it takes about >50* to make the lifter fall 0.120". But, when I do it from the heel of the cam, I get 0.122" plunge at 23*(1.5* cam retard) crank After TDC. So, I lock the cam in the journal, loosen the cam bolt, move the crank back to 20* ATDC, and retighten.
After going around two turns, the Porken tool is indicating that I am about 2* advance, which is exactly what I want. I check the 1-4 side and it also shows nearly 2* advance.
Since the 1-4 bank should be a bit further retarded because of heat-growth. So I want to move it but at this point, I'm scratching my head. The 1-4 bank were done with the plunge test starting on the radius heel of the cam, and we've got it nicely setup. I may retard it slightly for heat-growth, but right now I like the 5-8 setting.
Why is the WSM inaccurate? It says start at TDC and go 20* on the crank. This is only 10* of cam movement, and expecting to see 0.122" of movement on the 5-8 bank and 2.8MM(0.110") with that crank movement is not logical.
Saying the intake valve opens at 3* ATDC doesn't make sense on several levels. First, even though these cars were designed as a very low emission, waiting this long to open the intake valve is inefficient. Yes, I know that a 4VPC makes a difference in scavenging, but 3* After? Uhuh, I'm not buying.
Do you see what I'm saying? If you move the crank 20*, starting from TDC to 20* ATDC, the 1-4 will move x amount and the 5-8 cams will also move x amount. You can't move a cold engine the same degrees and expect two different plunge depths unless the cams are profiled differently, which I guess I possible, but unlikely. The differing plunge depth is supposed to make up for heat-growth, and I would think, you want the lobe profile to be exactly the same on both banks.
The only way it makes sense, and the only way it works right is to start on the heel of the lobe(like a normal engine builder would) and advance the 5-8(or retard 1-4) so that the 20* crank setting produces a plunge of 0.122" and 0.110' respectively. This accounts for the heat-growth, and postulates that the lobes on the intake cams have the same profile, which I believe is accurate.
Please add your thoughts, if you've been here and done this. Thanks to Ken for developing the Porken tool, it has been very useful to verify things as we go through this.
<edited second to last para to correct lash value from 0.112 to 0.122>
Having perused WSM section 15-119 through 140-ish, covering the cam removal and assembly, I've gotten everything fine right up to the degreeing of the cam. In fact, I've got the 1-4 cam timed up nicely using the values in the book, with a slight modification. On the 5-8 set, I'm having issues.
We proceed through page 130 just fine. The tool lines up fine with 113mm between the casting ****, and the timing can be set grossly with the Porken tool. I've used the tool to set the pin for zero set with the crank at TDC. So far so good. The belt goes on, and now we are ready to double check the plunge setting with the dial indicator. Here's where things go bad.
l.Turn engine in direction of
rotation to TDC (cylinder No. 1 and 6. 90 degree cyl bank and using first throw for 1, and second crank throw for 6).
So we start with the crank on TDC, and the Porken tool hitting perfectly at the notch in the backing plate indicating a zero lash. At this point, we should set up the dial indicator to perform the plunge measurement.
2.In this position, the marks on
the camshaft gears and the flange
bearings must also be aligned.
True, I've just set that with the Porken tool and locked the pullys to the cams, with correct tension.
3.At the same time, check the marks
(older engines) or noses (newer
engines) on the camshafts.
Both marks point toward exhaust
side.
Yes.
4.Mount gauge with
cylinder head.
0 with 5 mm pretension hydraulic
tappet
intake valve.
Done(we are using inches, but we've set about 0.200" preload. As I do this, I notice on these cams that the lifter is already a bit on the opening ramp of the lobe, hmmmmmmm. This doesn't seem right at this point because the cam timing says that the cam(GT) opens at 3* AFTER TDC! My crank is on TDC, but the cam is already opening the 5-8 valve a bit.
II understand that these are hydraulic lifters so I wonder if there is a delay in valve opening due to the squish out of the oil in the lifter. But it doesn't seem like this is a common way to measure the delta of the valve opening. Anyway, we proceed.
Place gauge on hydraulic
cylinder 6 intake valve.
Cylinder bank 5 - 8
Specified value: 2.0 + 0.1 mm(this is the value for the S4, the GT specs are found later)
5.Turn the crankshaft on past
TDC (cylinder 1) while observing
gauge. Continue turning
engine until the lift is 1.6 +
0.1 mm. The 20" (after TDC,
cylinder 6) mark must now be
aligned with the index mark on
the drive belt cover.
This is where the train goes off the tracks. There is already some preload on the lifter. In fact, it's about 0.060" when crank is at TDC. So we start turning the crank bolt and by the time we move 0.122" plunge the crank indicates about 50* ATDC. It's supposed to be close to 20*, not 50*. Hmmm, strange.
So I go back to the way I've been degreeing cams since I was 13. I rotate the crank around so that the cam is on the heel. At this point, I prepare my plunge indicator, with no preload on the lifter like I had before. We've zero set while the lifter is on the heel, and now proceed to do the plunge. Guess what, as I rotate around I get ~0.122" right at 20* after TDC. Just like the book wants, except they prep the plunge reading at TDC. And, the specs say the cam won't open until 3* AFTER TDC! Neither of these sounds right.
Now, I go back to the Porken tool, because I'm in a quandary about the timing. We set it using that tool, and prepare to do another plunge test. Just like before, if we start at TDC and measure from there, it takes about >50* to make the lifter fall 0.120". But, when I do it from the heel of the cam, I get 0.122" plunge at 23*(1.5* cam retard) crank After TDC. So, I lock the cam in the journal, loosen the cam bolt, move the crank back to 20* ATDC, and retighten.
After going around two turns, the Porken tool is indicating that I am about 2* advance, which is exactly what I want. I check the 1-4 side and it also shows nearly 2* advance.
Since the 1-4 bank should be a bit further retarded because of heat-growth. So I want to move it but at this point, I'm scratching my head. The 1-4 bank were done with the plunge test starting on the radius heel of the cam, and we've got it nicely setup. I may retard it slightly for heat-growth, but right now I like the 5-8 setting.
Why is the WSM inaccurate? It says start at TDC and go 20* on the crank. This is only 10* of cam movement, and expecting to see 0.122" of movement on the 5-8 bank and 2.8MM(0.110") with that crank movement is not logical.
Saying the intake valve opens at 3* ATDC doesn't make sense on several levels. First, even though these cars were designed as a very low emission, waiting this long to open the intake valve is inefficient. Yes, I know that a 4VPC makes a difference in scavenging, but 3* After? Uhuh, I'm not buying.
Do you see what I'm saying? If you move the crank 20*, starting from TDC to 20* ATDC, the 1-4 will move x amount and the 5-8 cams will also move x amount. You can't move a cold engine the same degrees and expect two different plunge depths unless the cams are profiled differently, which I guess I possible, but unlikely. The differing plunge depth is supposed to make up for heat-growth, and I would think, you want the lobe profile to be exactly the same on both banks.
The only way it makes sense, and the only way it works right is to start on the heel of the lobe(like a normal engine builder would) and advance the 5-8(or retard 1-4) so that the 20* crank setting produces a plunge of 0.122" and 0.110' respectively. This accounts for the heat-growth, and postulates that the lobes on the intake cams have the same profile, which I believe is accurate.
Please add your thoughts, if you've been here and done this. Thanks to Ken for developing the Porken tool, it has been very useful to verify things as we go through this.
<edited second to last para to correct lash value from 0.112 to 0.122>
Last edited by docmirror; 09-27-2008 at 03:13 AM.
09-27-2008, 02:35 AM
#2
Nordschleife Master
Doc,
I used Porken's degree kit and had no issues at all. I actually thought it was quite easy. Of course your actually degreeing them in, I didn't do that, but again, this was on my GT and when all was said and done the marks lined up perfectly and the task was quite easy in the end. I did go over it a half dozen times or so and adjusted it but i don't recall having any issues whatsoever.
So if i had any suggestion for you, it would be to get ahold of one of Ken's tools
I used Porken's degree kit and had no issues at all. I actually thought it was quite easy. Of course your actually degreeing them in, I didn't do that, but again, this was on my GT and when all was said and done the marks lined up perfectly and the task was quite easy in the end. I did go over it a half dozen times or so and adjusted it but i don't recall having any issues whatsoever.
So if i had any suggestion for you, it would be to get ahold of one of Ken's tools
09-27-2008, 02:41 AM
#3
Rennlist Member
Doc, were you not paying attention to the my saga?
My problem with measuring the lifter depression and trying to find out the reason for the difference of the setting using the WSM vs the porken tool was that i kept on telling everone that i had measured the lifter movement from TDC to 20degrees after TDC and got the right 2mm movement. in fact, i only used this movment because the holbert cams were GT like and I wanted to mirror their settings. as it turns out, and 30 pages of the discussion later, Porken relalized from the video or description, that i was measuring the lifter depression at TDC and it does move before hand. REMEMBER, the spec for the cam is to open at 3 degrees before TDC, BUT, thats at 1mm opening!! so, at 3 degrees after TDC, it will have to open 1mm so it is already starting well before the TDC mark. in fact, even with my 85 cams that open at 11 degrees ATDC, they are open .013 at TDC! (on their way to open 2mm by 20 degrees past TDC)
I only got half way through your story, and thougth this might be your issue as well.
Mark
My problem with measuring the lifter depression and trying to find out the reason for the difference of the setting using the WSM vs the porken tool was that i kept on telling everone that i had measured the lifter movement from TDC to 20degrees after TDC and got the right 2mm movement. in fact, i only used this movment because the holbert cams were GT like and I wanted to mirror their settings. as it turns out, and 30 pages of the discussion later, Porken relalized from the video or description, that i was measuring the lifter depression at TDC and it does move before hand. REMEMBER, the spec for the cam is to open at 3 degrees before TDC, BUT, thats at 1mm opening!! so, at 3 degrees after TDC, it will have to open 1mm so it is already starting well before the TDC mark. in fact, even with my 85 cams that open at 11 degrees ATDC, they are open .013 at TDC! (on their way to open 2mm by 20 degrees past TDC)
I only got half way through your story, and thougth this might be your issue as well.
Mark
Well, if you've taken off the cams on a 928, and put them back on, I need some help. If you've actually had the cams off a GT or Club Sport and put them back on that would be ideal.
Having perused WSM section 15-119 through 140-ish, covering the cam removal and assembly, I've gotten everything fine right up to the degreeing of the cam. In fact, I've got the 1-4 cam timed up nicely using the values in the book, with a slight modification. On the 5-8 set, I'm having issues.
We proceed through page 130 just fine. The tool lines up fine with 113mm between the casting ****, and the timing can be set grossly with the Porken tool. I've used the tool to set the pin for zero set with the crank at TDC. So far so good. The belt goes on, and now we are ready to double check the plunge setting with the dial indicator. Here's where things go bad.
l.Turn engine in direction of
rotation to TDC (cylinder No. 1 and 6. 90 degree cyl bank and using first throw for 1, and second crank throw for 6).
So we start with the crank on TDC, and the Porken tool hitting perfectly at the notch in the backing plate indicating a zero lash. At this point, we should set up the dial indicator to perform the plunge measurement.
2.In this position, the marks on
the camshaft gears and the flange
bearings must also be aligned.
True, I've just set that with the Porken tool and locked the pullys to the cams, with correct tension.
3.At the same time, check the marks
(older engines) or noses (newer
engines) on the camshafts.
Both marks point toward exhaust
side.
Yes.
4.Mount gauge with
cylinder head.
0 with 5 mm pretension hydraulic
tappet
intake valve.
Done(we are using inches, but we've set about 0.200" preload. As I do this, I notice on these cams that the lifter is already a bit on the opening ramp of the lobe, hmmmmmmm. This doesn't seem right at this point because the cam timing says that the cam(GT) opens at 3* AFTER TDC! My crank is on TDC, but the cam is already opening the 5-8 valve a bit.
II understand that these are hydraulic lifters so I wonder if there is a delay in valve opening due to the squish out of the oil in the lifter. But it doesn't seem like this is a common way to measure the delta of the valve opening. Anyway, we proceed.
Place gauge on hydraulic
cylinder 6 intake valve.
Cylinder bank 5 - 8
Specified value: 2.0 + 0.1 mm(this is the value for the S4, the GT specs are found later)
5.Turn the crankshaft on past
TDC (cylinder 1) while observing
gauge. Continue turning
engine until the lift is 1.6 +
0.1 mm. The 20" (after TDC,
cylinder 6) mark must now be
aligned with the index mark on
the drive belt cover.
This is where the train goes off the tracks. There is already some preload on the lifter. In fact, it's about 0.060" when crank is at TDC. So we start turning the crank bolt and by the time we move 0.122" plunge the crank indicates about 50* ATDC. It's supposed to be close to 20*, not 50*. Hmmm, strange.
So I go back to the way I've been degreeing cams since I was 13. I rotate the crank around so that the cam is on the heel. At this point, I prepare my plunge indicator, with no preload on the lifter like I had before. We've zero set while the lifter is on the heel, and now proceed to do the plunge. Guess what, as I rotate around I get ~0.122" right at 20* after TDC. Just like the book wants, except they prep the plunge reading at TDC. And, the specs say the cam won't open until 3* AFTER TDC! Neither of these sounds right.
Now, I go back to the Porken tool, because I'm in a quandary about the timing. We set it using that tool, and prepare to do another plunge test. Just like before, if we start at TDC and measure from there, it takes about >50* to make the lifter fall 0.120". But, when I do it from the heel of the cam, I get 0.122" plunge at 23*(1.5* cam retard) crank After TDC. So, I lock the cam in the journal, loosen the cam bolt, move the crank back to 20* ATDC, and retighten.
After going around two turns, the Porken tool is indicating that I am about 2* advance, which is exactly what I want. I check the 1-4 side and it also shows nearly 2* advance.
Since the 1-4 bank should be a bit further retarded because of heat-growth. So I want to move it but at this point, I'm scratching my head. The 1-4 bank were done with the plunge test starting on the radius heel of the cam, and we've got it nicely setup. I may retard it slightly for heat-growth, but right now I like the 5-8 setting.
Why is the WSM inaccurate? It says start at TDC and go 20* on the crank. This is only 10* of cam movement, and expecting to see 0.122" of movement on the 5-8 bank and 2.8MM(0.110") with that crank movement is not logical.
Saying the intake valve opens at 3* ATDC doesn't make sense on several levels. First, even though these cars were designed as a very low emission, waiting this long to open the intake valve is inefficient. Yes, I know that a 4VPC makes a difference in scavenging, but 3* After? Uhuh, I'm not buying.
Do you see what I'm saying? If you move the crank 20*, starting from TDC to 20* ATDC, the 1-4 will move x amount and the 5-8 cams will also move x amount. You can't move a cold engine the same degrees and expect two different plunge depths unless the cams are profiled differently, which I guess I possible, but unlikely. The differing plunge depth is supposed to make up for heat-growth, and I would think, you want the lobe profile to be exactly the same on both banks.
The only way it makes sense, and the only way it works right is to start on the heel of the lobe(like a normal engine builder would) and advance the 5-8(or retard 1-4) so that the 20* crank setting produces a plunge of 0.112" and 0.110' respectively. This accounts for the heat-growth, and postulates that the lobes on the intake cams have the same profile, which I believe is accurate.
Please add your thoughts, if you've been here and done this. Thanks to Ken for developing the Porken tool, it has been very useful to verify things as we go through this.
Having perused WSM section 15-119 through 140-ish, covering the cam removal and assembly, I've gotten everything fine right up to the degreeing of the cam. In fact, I've got the 1-4 cam timed up nicely using the values in the book, with a slight modification. On the 5-8 set, I'm having issues.
We proceed through page 130 just fine. The tool lines up fine with 113mm between the casting ****, and the timing can be set grossly with the Porken tool. I've used the tool to set the pin for zero set with the crank at TDC. So far so good. The belt goes on, and now we are ready to double check the plunge setting with the dial indicator. Here's where things go bad.
l.Turn engine in direction of
rotation to TDC (cylinder No. 1 and 6. 90 degree cyl bank and using first throw for 1, and second crank throw for 6).
So we start with the crank on TDC, and the Porken tool hitting perfectly at the notch in the backing plate indicating a zero lash. At this point, we should set up the dial indicator to perform the plunge measurement.
2.In this position, the marks on
the camshaft gears and the flange
bearings must also be aligned.
True, I've just set that with the Porken tool and locked the pullys to the cams, with correct tension.
3.At the same time, check the marks
(older engines) or noses (newer
engines) on the camshafts.
Both marks point toward exhaust
side.
Yes.
4.Mount gauge with
cylinder head.
0 with 5 mm pretension hydraulic
tappet
intake valve.
Done(we are using inches, but we've set about 0.200" preload. As I do this, I notice on these cams that the lifter is already a bit on the opening ramp of the lobe, hmmmmmmm. This doesn't seem right at this point because the cam timing says that the cam(GT) opens at 3* AFTER TDC! My crank is on TDC, but the cam is already opening the 5-8 valve a bit.
II understand that these are hydraulic lifters so I wonder if there is a delay in valve opening due to the squish out of the oil in the lifter. But it doesn't seem like this is a common way to measure the delta of the valve opening. Anyway, we proceed.
Place gauge on hydraulic
cylinder 6 intake valve.
Cylinder bank 5 - 8
Specified value: 2.0 + 0.1 mm(this is the value for the S4, the GT specs are found later)
5.Turn the crankshaft on past
TDC (cylinder 1) while observing
gauge. Continue turning
engine until the lift is 1.6 +
0.1 mm. The 20" (after TDC,
cylinder 6) mark must now be
aligned with the index mark on
the drive belt cover.
This is where the train goes off the tracks. There is already some preload on the lifter. In fact, it's about 0.060" when crank is at TDC. So we start turning the crank bolt and by the time we move 0.122" plunge the crank indicates about 50* ATDC. It's supposed to be close to 20*, not 50*. Hmmm, strange.
So I go back to the way I've been degreeing cams since I was 13. I rotate the crank around so that the cam is on the heel. At this point, I prepare my plunge indicator, with no preload on the lifter like I had before. We've zero set while the lifter is on the heel, and now proceed to do the plunge. Guess what, as I rotate around I get ~0.122" right at 20* after TDC. Just like the book wants, except they prep the plunge reading at TDC. And, the specs say the cam won't open until 3* AFTER TDC! Neither of these sounds right.
Now, I go back to the Porken tool, because I'm in a quandary about the timing. We set it using that tool, and prepare to do another plunge test. Just like before, if we start at TDC and measure from there, it takes about >50* to make the lifter fall 0.120". But, when I do it from the heel of the cam, I get 0.122" plunge at 23*(1.5* cam retard) crank After TDC. So, I lock the cam in the journal, loosen the cam bolt, move the crank back to 20* ATDC, and retighten.
After going around two turns, the Porken tool is indicating that I am about 2* advance, which is exactly what I want. I check the 1-4 side and it also shows nearly 2* advance.
Since the 1-4 bank should be a bit further retarded because of heat-growth. So I want to move it but at this point, I'm scratching my head. The 1-4 bank were done with the plunge test starting on the radius heel of the cam, and we've got it nicely setup. I may retard it slightly for heat-growth, but right now I like the 5-8 setting.
Why is the WSM inaccurate? It says start at TDC and go 20* on the crank. This is only 10* of cam movement, and expecting to see 0.122" of movement on the 5-8 bank and 2.8MM(0.110") with that crank movement is not logical.
Saying the intake valve opens at 3* ATDC doesn't make sense on several levels. First, even though these cars were designed as a very low emission, waiting this long to open the intake valve is inefficient. Yes, I know that a 4VPC makes a difference in scavenging, but 3* After? Uhuh, I'm not buying.
Do you see what I'm saying? If you move the crank 20*, starting from TDC to 20* ATDC, the 1-4 will move x amount and the 5-8 cams will also move x amount. You can't move a cold engine the same degrees and expect two different plunge depths unless the cams are profiled differently, which I guess I possible, but unlikely. The differing plunge depth is supposed to make up for heat-growth, and I would think, you want the lobe profile to be exactly the same on both banks.
The only way it makes sense, and the only way it works right is to start on the heel of the lobe(like a normal engine builder would) and advance the 5-8(or retard 1-4) so that the 20* crank setting produces a plunge of 0.112" and 0.110' respectively. This accounts for the heat-growth, and postulates that the lobes on the intake cams have the same profile, which I believe is accurate.
Please add your thoughts, if you've been here and done this. Thanks to Ken for developing the Porken tool, it has been very useful to verify things as we go through this.
09-27-2008, 02:48 AM
#4
Rennlist Member
Again, the issue in the 2nd paragraph here is becuase the book tells you (in their sloppy fashion) to set the gauge at TDC and then rotate it 380 degrees to get the full plunge of the lifter. the lifter presses against the cam via the lifter spring. its compressed. it doesnt matter where the valve is, as it will change when it gets pumped up. think of the lifter as something that just follows the cam lobe very accurately.
This is where the train goes off the tracks. There is already some preload on the lifter. In fact, it's about 0.060" when crank is at TDC. So we start turning the crank bolt and by the time we move 0.122" plunge the crank indicates about 50* ATDC. It's supposed to be close to 20*, not 50*. Hmmm, strange.
So I go back to the way I've been degreeing cams since I was 13. I rotate the crank around so that the cam is on the heel. At this point, I prepare my plunge indicator, with no preload on the lifter like I had before. We've zero set while the lifter is on the heel, and now proceed to do the plunge. Guess what, as I rotate around I get ~0.122" right at 20* after TDC. Just like the book wants, except they prep the plunge reading at TDC. And, the specs say the cam won't open until 3* AFTER TDC! Neither of these sounds right.
.
So I go back to the way I've been degreeing cams since I was 13. I rotate the crank around so that the cam is on the heel. At this point, I prepare my plunge indicator, with no preload on the lifter like I had before. We've zero set while the lifter is on the heel, and now proceed to do the plunge. Guess what, as I rotate around I get ~0.122" right at 20* after TDC. Just like the book wants, except they prep the plunge reading at TDC. And, the specs say the cam won't open until 3* AFTER TDC! Neither of these sounds right.
.
09-27-2008, 02:54 AM
#5
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
Mark, as I read your post, it says you got 2mm plunge on a 20* rotation from TDC to 20* ATDC. The correct movement is either 2.8 or 3.1mm depending on the bank you are working on.
If you didn't read all the way through, you missed some critical statements. First, unless the cams are different profile(not likely) for the different banks, when you move the crank 20*, you will get the same plunge movement on both sides.
Next, if you said you got 2mm, that is only about 60% of the expected movement, and close to what I saw with a 20* crank throw. Your readings seem to mirror mine. I read part of your post, but frankly I didn't slog through it all. Let's give this thread a bit of time to age, and see what comes of it.
If you didn't read all the way through, you missed some critical statements. First, unless the cams are different profile(not likely) for the different banks, when you move the crank 20*, you will get the same plunge movement on both sides.
Next, if you said you got 2mm, that is only about 60% of the expected movement, and close to what I saw with a 20* crank throw. Your readings seem to mirror mine. I read part of your post, but frankly I didn't slog through it all. Let's give this thread a bit of time to age, and see what comes of it.
09-27-2008, 02:59 AM
#6
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
Again, the issue in the 2nd paragraph here is becuase the book tells you (in their sloppy fashion) to set the gauge at TDC and then rotate it 380 degrees to get the full plunge of the lifter. the lifter presses against the cam via the lifter spring. its compressed. it doesnt matter where the valve is, as it will change when it gets pumped up. think of the lifter as something that just follows the cam lobe very accurately.
mk
mk
I was reading it as 'move the crank only 20* and you will plunge 2.8mm'. That ain't ever going to happen due to the preload at TDC. I believe I've had a Eureka moment, because now we add in the delta from the heel to the TDC point.
It's still funny that they put the gauge on when you are at TDC, and not somewhere on the heel radius. Crappy writing.
09-27-2008, 03:00 AM
#7
Rennlist Member
Sorry, i was thinking 85 cams at 2mm. with the GT cams at 3.1mm, you still have the same issue. at TDC to 20 degrees, there is movement that you are not capturing before TDC. meaning. the easiest way to catch the missing movement, is to 0 the guage at about 45 degrees BTDC. that way, you are for sure, on the back side of the cam lobe. in order to make the 3.1 degree movement, it will start moving, quite dramtically before it gets to TDC Actually, you might see, .005" movement at 20 degrees BTDC, and near .040" at TDC! (rough guesses, but you get the point) Both sides should be identical . The porken tool will allow you to set the passenger side off 1 or 2 degrees for engine expansion.
mk
mk
Mark, as I read your post, it says you got 2mm plunge on a 20* rotation from TDC to 20* ATDC. The correct movement is either 2.8 or 3.1mm depending on the bank you are working on.
If you didn't read all the way through, you missed some critical statements. First, unless the cams are different profile(not likely) for the different banks, when you move the crank 20*, you will get the same plunge movement on both sides.
Next, if you said you got 2mm, that is only about 60% of the expected movement, and close to what I saw with a 20* crank throw. Your readings seem to mirror mine. I read part of your post, but frankly I didn't slog through it all. Let's give this thread a bit of time to age, and see what comes of it.
If you didn't read all the way through, you missed some critical statements. First, unless the cams are different profile(not likely) for the different banks, when you move the crank 20*, you will get the same plunge movement on both sides.
Next, if you said you got 2mm, that is only about 60% of the expected movement, and close to what I saw with a 20* crank throw. Your readings seem to mirror mine. I read part of your post, but frankly I didn't slog through it all. Let's give this thread a bit of time to age, and see what comes of it.
Trending Topics
09-27-2008, 03:04 AM
#8
Rennlist Member
I guess i wasnt going crazy!! I was fixated on the "TDC to 20degree ATDC" over and over, hundreds of crank revolutions, video taping, etc and it all came down to misinterpreting the WSM. they shouldnt even mention the "TDC" its a meaningless measurement point, but the only way they could stress going all the way around again to measure the lifter depression. What they should have said, was to set the gauage at 0 at 45degrees BTDC, as there is a mark there anyway and all would have been good!
anyway, i had one of those moments as well, and now understand why i got the initial measurements i did, why they were advanced vs the porken tool.
I think you got it.
have fun.
Mark
anyway, i had one of those moments as well, and now understand why i got the initial measurements i did, why they were advanced vs the porken tool.
I think you got it.
have fun.
Mark
So, you read this as going 380*? I read it as going only 20*. From TDC to 20* ATDC. If you are right, and I think you are, then my measurement is correct. Because once I get off the nose of the cam lobe, the indicator will ascend past where it was when we started at TDC. This would provide a total throw of 2.8(0r 3.1) from the heel of the lobe, to the 20* ATDC setting.
I was reading it as 'move the crank only 20* and you will plunge 2.8mm'. That ain't ever going to happen due to the preload at TDC. I believe I've had a Eureka moment, because now we add in the delta from the heel to the TDC point.
It's still funny that they put the gauge on when you are at TDC, and not somewhere on the heel radius. Crappy writing.
I was reading it as 'move the crank only 20* and you will plunge 2.8mm'. That ain't ever going to happen due to the preload at TDC. I believe I've had a Eureka moment, because now we add in the delta from the heel to the TDC point.
It's still funny that they put the gauge on when you are at TDC, and not somewhere on the heel radius. Crappy writing.
09-27-2008, 03:05 AM
#9
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
Doc,
I used Porken's degree kit and had no issues at all. I actually thought it was quite easy. Of course your actually degreeing them in, I didn't do that, but again, this was on my GT and when all was said and done the marks lined up perfectly and the task was quite easy in the end. I did go over it a half dozen times or so and adjusted it but i don't recall having any issues whatsoever.
So if i had any suggestion for you, it would be to get ahold of one of Ken's tools
I used Porken's degree kit and had no issues at all. I actually thought it was quite easy. Of course your actually degreeing them in, I didn't do that, but again, this was on my GT and when all was said and done the marks lined up perfectly and the task was quite easy in the end. I did go over it a half dozen times or so and adjusted it but i don't recall having any issues whatsoever.
So if i had any suggestion for you, it would be to get ahold of one of Ken's tools
I think Mark has led me on to the answer I need. The total plunge from the heel(any part of the conforming radius on the back of the cam) to the 20* ATDC mark is going to add up to the right depth. So, in a way, I was doing it right by starting at zero on the heel, and just rotating around to 20* ATDC for my plunge reading.
<edited; changed tolerance to 0.5 from 1.5 for the Porken tool(late, tired) >
Last edited by docmirror; 09-27-2008 at 11:03 AM.
09-27-2008, 03:07 AM
#10
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
Sorry, i was thinking 85 cams at 2mm. with the GT cams at 3.1mm, you still have the same issue. at TDC to 20 degrees, there is movement that you are not capturing before TDC. meaning. the easiest way to catch the missing movement, is to 0 the guage at about 45 degrees BTDC. that way, you are for sure, on the back side of the cam lobe. in order to make the 3.1 degree movement, it will start moving, quite dramtically before it gets to TDC Actually, you might see, .005" movement at 20 degrees BTDC, and near .040" at TDC! (rough guesses, but you get the point) Both sides should be identical . The porken tool will allow you to set the passenger side off 1 or 2 degrees for engine expansion.
mk
mk
QED. I can sleep now.
09-27-2008, 03:13 AM
#11
Rennlist Member
Glad I could help!
Sleep! I lost a lot over this one!
Glad its all over now!
MK
Sleep! I lost a lot over this one!
Glad its all over now!
MK
PRECISELY! And well done, with the 380* statement. It will 'capture' both the plus delta from TDC to 20* ATDC, and it will 'capture' the delta from the heel UP TO the TDC point. Thus totaling either 2.8 or 3.1 as defined by the advance of the cam in relation to the crank.
QED. I can sleep now.
QED. I can sleep now.
09-27-2008, 06:02 AM
#12
Addict
Rennlist Member
Rennlist Member
II understand that these are hydraulic lifters so I wonder if there is a delay in valve opening due to the squish out of the oil in the lifter. But it doesn't seem like this is a common way to measure the delta of the valve opening. Anyway, we proceed.
Hydraulic lifters in theory transmit the actions of the cam onto the top of the lifter perfectly thus causing the valves to replicate the movement of the top of the lifter.
In reality the lifter removes some of the movement to varying degrees depnding upon wear in the lifter etc but there is nothing you can do about this, further it doesn't affect your cam timing measurements and measuing this effect on actual valve movement would be even more difficult than persuading MK not to run Amsoil in his engine.
09-27-2008, 10:54 AM
#13
I think we got it right Doc when we moved the measurement from the 45 (lobe off) to the 122" with cranking it for measurement.
After seeing this all in action, I think I actually understand how it all works and I now understand Marks thread now.
Thanks for the instructions Doc.... You engine is ready to go, just need to put the belt back on and we can shove it in the car. I buttoned it up last night.
After seeing this all in action, I think I actually understand how it all works and I now understand Marks thread now.
Thanks for the instructions Doc.... You engine is ready to go, just need to put the belt back on and we can shove it in the car. I buttoned it up last night.
09-27-2008, 11:57 AM
#14
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
928 four valve cam timing for humans.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tools; 17mm socket, 27-30 combo wrenches, dial indicator, Star-8 bit for cam journal, glossy magazine cover.
1. Perform WSM up to page 15-130.
2. Set both bank cam wheels to center of adjustment range in slot, tighten cam nut while counterholding exhaust cam.
3. Set tick marks on cam wheel to align with tick marks on backing plate. Install and tension belt at TDC.
4. Rotate carefully two full turns back to TDC. Stop if you encounter solid resistance, and investigate.
5. Turn CW until #6 intake cam has the lobe pointing straight up from lifter(cam on heel of lobe).
6. Set up dial indicator on lifter of intake #6 with preload(or plunge) of >4mm. Indicator shaft perpendicular to lifter face. Zero gauge.
7. Ignore crank location. Rotate crank clockwise slowly until dial indicator has unwound according to the table below;
~~~~~~GT/CS cams = 3.1mm
~~~~~~85-86.5 cams = 2.0mm
~~~~~~S4 cams = 2.0mm
8. Tear 20 x 40mm strip from glossy magazine cover. Remove rear journal cap from #6 intake cam and fold strip once to ~20x20 square, then lay on journal. Install and snug journal cap back on over strip to lock cam.
********WARNING - DO NOT TURN CRANKSHAFT YET*********
9. Counterhold #6 exhaust cam, and loosen cam bolt 17mm with socket. Insure the three 5mm screws are out or loose on camwheel.
10. gently rotate the crank either direction to 20 degrees after TDC. Insure you use the AFTER TDC mark, not the before TDC mark.
11. Check belt tension, adjust now if needed.
12. Counterhold exhaust cam, tighten cam 17mm bolt on camwheel.
13. Remove glossy magazine strip from rear cam journal, reinstall journal cap.
14. Rotate crank so that cam lobe on cyl #1 is pointing straight up from lifter.
15. Set dial indicator up on intake lifter Cyl #1 with > 4mm preload and indicator shaft perpendicular to lifter face.
16. Ignore crank location. Rotate crank clockwise slowly until dial indicator has unwound according to the table below;
~~~~~~GT/CS cams = 2.8mm
~~~~~~85-86.5 cams = 1.6mm
~~~~~~S4 cams = 1.8mm
17. repeat steps 8-13 above, substituting cyl #1 in place of cyl #6.
*****DO NOT MOVE CRANK UNTIL CAMWHEEL BOLT IS LOOSE*****.
18. Recheck tension, insure cam journal caps are free of magazine strips, insure journal caps are tight, and rotate back to TDC. The ticks in the cams and backing plates should line up closely, depending on wear of camwheels, and crank and oil gears.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Tools; 17mm socket, 27-30 combo wrenches, dial indicator, Star-8 bit for cam journal, glossy magazine cover.
1. Perform WSM up to page 15-130.
2. Set both bank cam wheels to center of adjustment range in slot, tighten cam nut while counterholding exhaust cam.
3. Set tick marks on cam wheel to align with tick marks on backing plate. Install and tension belt at TDC.
4. Rotate carefully two full turns back to TDC. Stop if you encounter solid resistance, and investigate.
5. Turn CW until #6 intake cam has the lobe pointing straight up from lifter(cam on heel of lobe).
6. Set up dial indicator on lifter of intake #6 with preload(or plunge) of >4mm. Indicator shaft perpendicular to lifter face. Zero gauge.
7. Ignore crank location. Rotate crank clockwise slowly until dial indicator has unwound according to the table below;
~~~~~~GT/CS cams = 3.1mm
~~~~~~85-86.5 cams = 2.0mm
~~~~~~S4 cams = 2.0mm
8. Tear 20 x 40mm strip from glossy magazine cover. Remove rear journal cap from #6 intake cam and fold strip once to ~20x20 square, then lay on journal. Install and snug journal cap back on over strip to lock cam.
********WARNING - DO NOT TURN CRANKSHAFT YET*********
9. Counterhold #6 exhaust cam, and loosen cam bolt 17mm with socket. Insure the three 5mm screws are out or loose on camwheel.
10. gently rotate the crank either direction to 20 degrees after TDC. Insure you use the AFTER TDC mark, not the before TDC mark.
11. Check belt tension, adjust now if needed.
12. Counterhold exhaust cam, tighten cam 17mm bolt on camwheel.
13. Remove glossy magazine strip from rear cam journal, reinstall journal cap.
14. Rotate crank so that cam lobe on cyl #1 is pointing straight up from lifter.
15. Set dial indicator up on intake lifter Cyl #1 with > 4mm preload and indicator shaft perpendicular to lifter face.
16. Ignore crank location. Rotate crank clockwise slowly until dial indicator has unwound according to the table below;
~~~~~~GT/CS cams = 2.8mm
~~~~~~85-86.5 cams = 1.6mm
~~~~~~S4 cams = 1.8mm
17. repeat steps 8-13 above, substituting cyl #1 in place of cyl #6.
*****DO NOT MOVE CRANK UNTIL CAMWHEEL BOLT IS LOOSE*****.
18. Recheck tension, insure cam journal caps are free of magazine strips, insure journal caps are tight, and rotate back to TDC. The ticks in the cams and backing plates should line up closely, depending on wear of camwheels, and crank and oil gears.
Last edited by docmirror; 09-27-2008 at 12:23 PM.
09-27-2008, 11:59 AM
#15
Shameful Thread Killer
Rennlist Member
Rennlist Member
Thread Starter
Sean and I were puzzled to say the least yesterday. The Porken tool was our fallback when I couldn't get the plunge readings I wanted. Once we did it using the heel of the cam, it all fell into place. Sean has remarkable patience. I was into beer #5, and still pretty frazzled about this.