Engine Timing - 32vr & Dial Gauge Disagreement (Issue Found I Think)
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Engine Timing - 32vr & Dial Gauge Disagreement (Issue Found I Think)
I set about checking the timing on my car - model year 1987 - with a dial indicator set up as well as the 32vr. I set up the devices on cylinder bank 5-8 and followed the procedure for each individually. I used each method twice to be sure it was repeatable...and the results for each test were similar.
As is shown in the photos below, I having an issue making the dial indicator and 32vr agree with each other. The 32vr is showing near spot on timing with maybe 1 degree advance timing. On the other hand, at 2|0 the dial indicator is showing 1.425mm deflection on a cylinder bank that should be 2.0mm +/- 0.1mm. I have posted photos of each step in the process so you can see what I saw.
Note: I have a Porkensioner installed
Any thoughts on what might be going on here?
Dial Indicator Method
Procedure Used - Rotated engine to TDC. Installed dial indicator on intake valve of cylinder #6 (photo in WSM shows this to be the valve further forward on #6) and set gauge to zero with 5mm pretension. Made best effort to align dial gauge with cylinder.
Initial Position Balancer
http://www.flickr.com/photos/51967142@N00/5299837155/
Initial Position Gauge
http://www.flickr.com/photos/51967142@N00/5299837091/
Gauge Allignment
http://www.flickr.com/photos/51967142@N00/5300433132/
Read Position (based on 2|0)
http://www.flickr.com/photos/51967142@N00/5300433062/
Gauge showing deflection at 2|0 - shows 1.425 deflection...should be 2.0 +/- 0.1mm
http://www.flickr.com/photos/51967142@N00/5299836907/
Balancer position with dial indicator at approximate 2.0mm deflection (went a touch past zero)
http://www.flickr.com/photos/51967142@N00/5299836825/
Dial indicator at about 2.0mm deflection
http://www.flickr.com/photos/51967142@N00/5299836761/
32vr Method
Procedure - Rotated engine to TDC and installed 32vr. Manual calls for even tightening of bolts so I used a torque wrench and 25 inch-lbs which was about right for the 1/8 to 1/4 turn of the bolt specified. Installed the reader and took reading which was about 1 degree advanced.
Blancer Position - TDC
http://www.flickr.com/photos/51967142@N00/5300432754/
32vr Reading
http://www.flickr.com/photos/51967142@N00/5300432680/
As is shown in the photos below, I having an issue making the dial indicator and 32vr agree with each other. The 32vr is showing near spot on timing with maybe 1 degree advance timing. On the other hand, at 2|0 the dial indicator is showing 1.425mm deflection on a cylinder bank that should be 2.0mm +/- 0.1mm. I have posted photos of each step in the process so you can see what I saw.
Note: I have a Porkensioner installed
Any thoughts on what might be going on here?
Dial Indicator Method
Procedure Used - Rotated engine to TDC. Installed dial indicator on intake valve of cylinder #6 (photo in WSM shows this to be the valve further forward on #6) and set gauge to zero with 5mm pretension. Made best effort to align dial gauge with cylinder.
Initial Position Balancer
http://www.flickr.com/photos/51967142@N00/5299837155/
Initial Position Gauge
http://www.flickr.com/photos/51967142@N00/5299837091/
Gauge Allignment
http://www.flickr.com/photos/51967142@N00/5300433132/
Read Position (based on 2|0)
http://www.flickr.com/photos/51967142@N00/5300433062/
Gauge showing deflection at 2|0 - shows 1.425 deflection...should be 2.0 +/- 0.1mm
http://www.flickr.com/photos/51967142@N00/5299836907/
Balancer position with dial indicator at approximate 2.0mm deflection (went a touch past zero)
http://www.flickr.com/photos/51967142@N00/5299836825/
Dial indicator at about 2.0mm deflection
http://www.flickr.com/photos/51967142@N00/5299836761/
32vr Method
Procedure - Rotated engine to TDC and installed 32vr. Manual calls for even tightening of bolts so I used a torque wrench and 25 inch-lbs which was about right for the 1/8 to 1/4 turn of the bolt specified. Installed the reader and took reading which was about 1 degree advanced.
Blancer Position - TDC
http://www.flickr.com/photos/51967142@N00/5300432754/
32vr Reading
http://www.flickr.com/photos/51967142@N00/5300432680/
Last edited by aaddpp; 02-05-2011 at 06:06 PM.
#2
Team Owner
you should try this match with the used belt,
as it will be prestretched.
It may give different readings
as it will be prestretched.
It may give different readings
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Kens tool is so straight forward so I can't find any error there, so there must be something on the dial side - just guessing.
#6
Rennlist Member
One thought-- the dial-indicator is on the intake cam, while the 32v'r measures the exhaust cam-- and your chain tensioner is not pumped up, because there is no oil pressure. So the chain will either be slack on the top or bottom, depending on which intake valves are doing what. That will make a few degrees difference, no??
#7
Inventor
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A new belt will have about 1-2° advance until it is 'seasoned'.
Is the engine at T|0, #1 cylinder? This is where the 32V'r is most accurate.
Differing valve openings at #6 T|0, and at both 4|5 settings stretch the belt differently, changing the reading up to 2°.
Procedure - Rotated engine to TDC and installed 32vr. Manual calls for even tightening of bolts so I used a torque wrench and 25 inch-lbs which was about right for the 1/8 to 1/4 turn of the bolt specified. Installed the reader and took reading which was about 1 degree advanced.
Differing valve openings at #6 T|0, and at both 4|5 settings stretch the belt differently, changing the reading up to 2°.
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#8
Drifting
aaddpp,
OK, they are not in agreement. Using 32vr, what is the difference in degrees for cyl #6? Eyeball from photo, looks like 5 crank degrees (2.5 cam degrees) difference.
Once you calibrate the 32vr against the WSM and your new belt, then later with seasoned belt, you can recheck or reset cam timing using only the 32vr tool.
OK, they are not in agreement. Using 32vr, what is the difference in degrees for cyl #6? Eyeball from photo, looks like 5 crank degrees (2.5 cam degrees) difference.
Once you calibrate the 32vr against the WSM and your new belt, then later with seasoned belt, you can recheck or reset cam timing using only the 32vr tool.
Last edited by borland; 12-28-2010 at 10:06 PM.
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Have your cams been out recently? If so - and maybe even if not - check that your intake and exhaust cams are indexed correctly. See WSM 15-127. It is very difficult to eyeball the marks with the engine in the car. 1/2 chain link off looks correct when it is, in fact, not. When the index marks on the two cams are aligned there should be exactly six chain links between the two marks. WSM shows 5 full links and two half links on either side.
#10
From another thread:
There are errors (tolerance) with the indexing of the cam lobe to the key way, the key itself, the hub keyway to the hub spider, the drilling of the bolt holes on the hub and then the position of the back cover. Even if everything is within tolerance the total of all the tolerances could stack up to a noticeable discrepancy. One of the 944 sites claims that they have found up to 3 degrees mismatch of the cam to the hub. I don't have anything against Ken or his tool. Anybody or anything that makes 928 ownership easier is a good thing. I just don't understand how the Porken tool can do it's job unless it allows for these sources of error.
Its keying-off the threaded holes behind the gears.
Those holes are fixed with respect to the camshaft profiles.
Those holes are fixed with respect to the camshaft profiles.
The pointer is relative to the position of the back cover, which can change a little bit from engine to engine or even on the same engine if the back cover has been off.
#11
Rennlist Member
With all due respect to the original poster, this makes no sense:
I don't know much about grinding cams, but I would think that the index of the keyway relative to the cam lobes is fundamental to the cam-grinding art.
As for the rest, the key is a snug fit in both cam and hub, and the hub itself was certainly made with a CNC machine, even in the 80's. It's possible that the hub was machined on one machine and then the holes drilled and threaded on a different machine, with potential errors, but that doesn't seem likely-- unless it was Fritz with a drill-press. And even if it was a different operation, they would have to index off of some feature, and the keyway is about all there is. So I am not buying it.
I think the answer, in this case, lies with the intake vs. exhaust cam.
aaddpp, if you are not doing anything this evening, could you repeat the check with the exhaust cam?
There are errors (tolerance) with the indexing of the cam lobe to the key way, the key itself, the hub keyway to the hub spider, the drilling of the bolt holes on the hub and then the position of the back cover.
As for the rest, the key is a snug fit in both cam and hub, and the hub itself was certainly made with a CNC machine, even in the 80's. It's possible that the hub was machined on one machine and then the holes drilled and threaded on a different machine, with potential errors, but that doesn't seem likely-- unless it was Fritz with a drill-press. And even if it was a different operation, they would have to index off of some feature, and the keyway is about all there is. So I am not buying it.
I think the answer, in this case, lies with the intake vs. exhaust cam.
aaddpp, if you are not doing anything this evening, could you repeat the check with the exhaust cam?
#13
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With all due respect to the original poster, this makes no sense:
I don't know much about grinding cams, but I would think that the index of the keyway relative to the cam lobes is fundamental to the cam-grinding art.
As for the rest, the key is a snug fit in both cam and hub, and the hub itself was certainly made with a CNC machine, even in the 80's. It's possible that the hub was machined on one machine and then the holes drilled and threaded on a different machine, with potential errors, but that doesn't seem likely-- unless it was Fritz with a drill-press. And even if it was a different operation, they would have to index off of some feature, and the keyway is about all there is. So I am not buying it.
I think the answer, in this case, lies with the intake vs. exhaust cam.
aaddpp, if you are not doing anything this evening, could you repeat the check with the exhaust cam?
I don't know much about grinding cams, but I would think that the index of the keyway relative to the cam lobes is fundamental to the cam-grinding art.
As for the rest, the key is a snug fit in both cam and hub, and the hub itself was certainly made with a CNC machine, even in the 80's. It's possible that the hub was machined on one machine and then the holes drilled and threaded on a different machine, with potential errors, but that doesn't seem likely-- unless it was Fritz with a drill-press. And even if it was a different operation, they would have to index off of some feature, and the keyway is about all there is. So I am not buying it.
I think the answer, in this case, lies with the intake vs. exhaust cam.
aaddpp, if you are not doing anything this evening, could you repeat the check with the exhaust cam?
#14
With all due respect to the original poster, this makes no sense:
I don't know much about grinding cams, but I would think that the index of the keyway relative to the cam lobes is fundamental to the cam-grinding art.
As for the rest, the key is a snug fit in both cam and hub, and the hub itself was certainly made with a CNC machine, even in the 80's. It's possible that the hub was machined on one machine and then the holes drilled and threaded on a different machine, with potential errors, but that doesn't seem likely-- unless it was Fritz with a drill-press. And even if it was a different operation, they would have to index off of some feature, and the keyway is about all there is. So I am not buying it.
I think the answer, in this case, lies with the intake vs. exhaust cam.
aaddpp, if you are not doing anything this evening, could you repeat the check with the exhaust cam?
I don't know much about grinding cams, but I would think that the index of the keyway relative to the cam lobes is fundamental to the cam-grinding art.
As for the rest, the key is a snug fit in both cam and hub, and the hub itself was certainly made with a CNC machine, even in the 80's. It's possible that the hub was machined on one machine and then the holes drilled and threaded on a different machine, with potential errors, but that doesn't seem likely-- unless it was Fritz with a drill-press. And even if it was a different operation, they would have to index off of some feature, and the keyway is about all there is. So I am not buying it.
I think the answer, in this case, lies with the intake vs. exhaust cam.
aaddpp, if you are not doing anything this evening, could you repeat the check with the exhaust cam?