Anyone with technical knowledge of the 928 engine want to talk?
12-15-2007, 10:29 AM
#1
Racer
Thread Starter
Anyone with technical knowledge of the 928 engine want to talk?
I am having a serious issue with cam timing. My fresh engine locked up. I have not dissambled it yet. I'm stepping back for a month to think about this and do some research.
I would like to discuss the timing belt gears and their relationship with anyone in the know. If you would like to talk pm me your phone number or I'll send you mine.
Anyone else that wants the story, I'll post the long version.
I have a 1980 euro S engine in my 914 that was running but needed a freshing and some valve work. I rebuilt the engine and used a very nice M28/12 block and crank with my S pistons, rods, heads and CIS. The heads were cut to approx 23.4mm.
Upon first start up it made a clicking noise like a stuck or failed lifter. The noise quit but the engine was smoking at cold start up and under hard excelleration About 800 miles of break in it self destructed and the results were very bad.
I had the damaged head repaired and reassembled another short block using my 1980 S block with the M28/12 US crank. I replaced a broken piston and a bent rod on #1 cylinder. The heads are now at 23mm. I'm using the 1.4mm porsche thick head gasket. I used a degree wheel and and a 2mm offset key on the right cam to aid in correcting the belt timing.
During the setup of the belt I thought I noticed a tight spot when approching 180 deg. while rotating the assembly. (wrench on the crank nut, plugs out)
I was suspect the lifter over the damaged valve on #1 cylinder may have been damaged. I pulled the euro cam housing and swapped on a US cam as a test. This seemed to do the trick. At and around 180 deg. I didn't notice the drag feeling. I changed the lifter for #1 on the euro head and re-installed it. That seemed to correct the issue.
As I was attempting to start the engine. As it fired I heard the familiar clicking sound. after a couple of attempts to start it it locked up.
(it only fired once & actually lock up while the start motor was cranking)
I pulled the plugs and put a wrench on the crank but could not turn it. The crank is around the 180 deg. of rotation....
So, I've check the marks several times during setup Balancer at O/T left cam lined up with the pointer directly under the distributor on the front cam housing, The right cam keyway lined up with the pointer on the front housing. the gear is off slightly but the offset key put the cam in phase.
After all this long explanation my questions are:
I changed the gears for the belt from the early square tooth to the late round tooth. The crank gear has a punch mark on one face.
Which way does the punch mark go?
Facing the block?
Facing the balancer?
If it's installed with the punch mark facing the wrong direct would it have any effect on the cam timing?
I don't understand why I'm have interference issues.
I would like to discuss the timing belt gears and their relationship with anyone in the know. If you would like to talk pm me your phone number or I'll send you mine.
Anyone else that wants the story, I'll post the long version.
I have a 1980 euro S engine in my 914 that was running but needed a freshing and some valve work. I rebuilt the engine and used a very nice M28/12 block and crank with my S pistons, rods, heads and CIS. The heads were cut to approx 23.4mm.
Upon first start up it made a clicking noise like a stuck or failed lifter. The noise quit but the engine was smoking at cold start up and under hard excelleration About 800 miles of break in it self destructed and the results were very bad.
I had the damaged head repaired and reassembled another short block using my 1980 S block with the M28/12 US crank. I replaced a broken piston and a bent rod on #1 cylinder. The heads are now at 23mm. I'm using the 1.4mm porsche thick head gasket. I used a degree wheel and and a 2mm offset key on the right cam to aid in correcting the belt timing.
During the setup of the belt I thought I noticed a tight spot when approching 180 deg. while rotating the assembly. (wrench on the crank nut, plugs out)
I was suspect the lifter over the damaged valve on #1 cylinder may have been damaged. I pulled the euro cam housing and swapped on a US cam as a test. This seemed to do the trick. At and around 180 deg. I didn't notice the drag feeling. I changed the lifter for #1 on the euro head and re-installed it. That seemed to correct the issue.
As I was attempting to start the engine. As it fired I heard the familiar clicking sound. after a couple of attempts to start it it locked up.
(it only fired once & actually lock up while the start motor was cranking)
I pulled the plugs and put a wrench on the crank but could not turn it. The crank is around the 180 deg. of rotation....
So, I've check the marks several times during setup Balancer at O/T left cam lined up with the pointer directly under the distributor on the front cam housing, The right cam keyway lined up with the pointer on the front housing. the gear is off slightly but the offset key put the cam in phase.
After all this long explanation my questions are:
I changed the gears for the belt from the early square tooth to the late round tooth. The crank gear has a punch mark on one face.
Which way does the punch mark go?
Facing the block?
Facing the balancer?
If it's installed with the punch mark facing the wrong direct would it have any effect on the cam timing?
I don't understand why I'm have interference issues.
12-15-2007, 12:47 PM
#3
Did you clay the pistons just to check what the clearance is?
What series heads are you using?
What series heads are you using?
12-15-2007, 12:59 PM
#5
Rennlist Member
Clearance is not really an issue, if it is timed right. (no matter how much the head or block has been shaved! (within reason) , or what heads you use. if it has clearance issues, you would probably see that when you are putting the timing belt on. remember, on our engines, the valves dont start traveling down until after TDC, and when they do, there will only be a max 2mm depression, even 20 degrees after TDC !! so, thats not what is hitting.
what you could have done, is siezed the pistons in the bore. did you use any starting fluid when trying to start the first time? are you posititve you didnt break a ring on assembly? does the engine move at all? can you rotate it backwards an 1" or two just to see if the lock up is something hittting, or in the cylinder, crank, or valve train?
did it just lock up or while it was starting did it start slower and slower and then stop? if it was the later, you could have pistons siezed in the bores.
edit: I read your post again and was curious of what caused the 800mile failure. the sticking feeling at the 180degree mark, and why by putting on a US cam, did that feeling go away. even though the offset key is small (how does that work by the way), could you have overcompensated for the lower head distance fit, because you did have a 1.4 mm head gasket . are you sure the retainers on all the valves are good? a dropped valve could jam into the cylinder very easily. Being able to rotate the engine backward could help determine where it is jammed up.
Mk
PS. IF it is the engine, we have a brand new one ready to go if you find out that its something serious in the shortblock.
what you could have done, is siezed the pistons in the bore. did you use any starting fluid when trying to start the first time? are you posititve you didnt break a ring on assembly? does the engine move at all? can you rotate it backwards an 1" or two just to see if the lock up is something hittting, or in the cylinder, crank, or valve train?
did it just lock up or while it was starting did it start slower and slower and then stop? if it was the later, you could have pistons siezed in the bores.
edit: I read your post again and was curious of what caused the 800mile failure. the sticking feeling at the 180degree mark, and why by putting on a US cam, did that feeling go away. even though the offset key is small (how does that work by the way), could you have overcompensated for the lower head distance fit, because you did have a 1.4 mm head gasket . are you sure the retainers on all the valves are good? a dropped valve could jam into the cylinder very easily. Being able to rotate the engine backward could help determine where it is jammed up.
Mk
PS. IF it is the engine, we have a brand new one ready to go if you find out that its something serious in the shortblock.
12-15-2007, 01:23 PM
#6
Racer
Thread Starter
12-15-2007, 01:45 PM
#7
Racer
Thread Starter
Clearance is not really an issue, if it is timed right. (no matter how much the head or block has been shaved! (within reason) , or what heads you use. if it has clearance issues, you would probably see that when you are putting the timing belt on. remember, on our engines, the valves dont start traveling down until after TDC, and when they do, there will only be a max 2mm depression, even 20 degrees after TDC !! so, thats not what is hitting.
what you could have done, is siezed the pistons in the bore. did you use any starting fluid when trying to start the first time?
No starting fluid. This did happen after I primed the injectors by depressing the flapper and letting the injectors squeal, This could have possibly washed the cylinders down. When I pulled the plugs they were wet.
are you posititve you didnt break a ring on assembly?
I'm not sure, I was very careful this time around as I thought that may have been the cause of my last failure.
does the engine move at all? can you rotate it backwards an 1" or two just to see if the lock up is something hittting, or in the cylinder, crank, or valve train?
Nope, I just tried to move it counter clockwise and the crank nut came loose. I didn't install the axles yet so I can't put it in gear and rock it backwards either.
did it just lock up or while it was starting did it start slower and slower and then stop? if it was the later, you could have pistons siezed in the bores.
Was cranking normal and just stopped
edit: I read your post again and was curious of what caused the 800mile failure. the sticking feeling at the 180degree mark, and why by putting on a US cam, did that feeling go away.
I just mocked up the US cam to see if the tight spot want away. And it seemed to. I took it back off before installing it in the car. After relubing the lifters in the euro head it seemed to go away.
even though the offset key is small (how does that work by the way), could you have overcompensated for the lower head distance fit, because you did have a 1.4 mm head gasket . are you sure the retainers on all the valves are good? a dropped valve could jam into the cylinder very easily. Being able to rotate the engine backward could help determine where it is jammed up.
Again, not sure, I'm not pulling the engine until after christmas. I have too much on my plate now.
Mk
PS. IF it is the engine, we have a brand new one ready to go if you find out that its something serious in the shortblock.
what you could have done, is siezed the pistons in the bore. did you use any starting fluid when trying to start the first time?
No starting fluid. This did happen after I primed the injectors by depressing the flapper and letting the injectors squeal, This could have possibly washed the cylinders down. When I pulled the plugs they were wet.
are you posititve you didnt break a ring on assembly?
I'm not sure, I was very careful this time around as I thought that may have been the cause of my last failure.
does the engine move at all? can you rotate it backwards an 1" or two just to see if the lock up is something hittting, or in the cylinder, crank, or valve train?
Nope, I just tried to move it counter clockwise and the crank nut came loose. I didn't install the axles yet so I can't put it in gear and rock it backwards either.
did it just lock up or while it was starting did it start slower and slower and then stop? if it was the later, you could have pistons siezed in the bores.
Was cranking normal and just stopped
edit: I read your post again and was curious of what caused the 800mile failure. the sticking feeling at the 180degree mark, and why by putting on a US cam, did that feeling go away.
I just mocked up the US cam to see if the tight spot want away. And it seemed to. I took it back off before installing it in the car. After relubing the lifters in the euro head it seemed to go away.
even though the offset key is small (how does that work by the way), could you have overcompensated for the lower head distance fit, because you did have a 1.4 mm head gasket . are you sure the retainers on all the valves are good? a dropped valve could jam into the cylinder very easily. Being able to rotate the engine backward could help determine where it is jammed up.
Again, not sure, I'm not pulling the engine until after christmas. I have too much on my plate now.
Mk
PS. IF it is the engine, we have a brand new one ready to go if you find out that its something serious in the shortblock.
As always Mark you've brought up some good points and I appreciate your help.
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12-15-2007, 01:52 PM
#8
Rennlist Member
can you go over the original failure. how did the piston "break" and the rod bend? failed 2/6 bearing? Then, how did the head get damaged. what type of fix did you do on the heads?
smoke on the acceleration could be ring issues. did it run rough?
on the second rebuild. you got another M28-12 block? could there be clearnce issues with the crank and the block?
as a note, that might not apply, with the newer, larger oiling hole crank, when used on the early block, there were some serious clearance issues that were easy to fix.
Mk
smoke on the acceleration could be ring issues. did it run rough?
on the second rebuild. you got another M28-12 block? could there be clearnce issues with the crank and the block?
as a note, that might not apply, with the newer, larger oiling hole crank, when used on the early block, there were some serious clearance issues that were easy to fix.
Mk
12-15-2007, 02:08 PM
#9
Rennlist Member
certainly possible. the shop working on scots original rebuild did this. we had a coil wire reversed and the guy kept on starting the engine. looking down the holes, you could see a puddle of fuel. this is one of the reason i like to use a mix of assembly lube (redline) and oil on the cylinders or pistons skirts, just as a precaution, and as i mentioned it probalby has very little risk to not breaking in the rings properly with Alusil bores. (contrary to Brendans textbook advice 
)
one way to back the engine a bit, is to use a fat flat head screwdriver on the starter ring through the peak hole area. if it is jammed in both directions, it probably is block or crank related, especially if you can move it a few inches and its really stiff both ways. I hope that it is not, but the only thing in the valve train that can do what you describe is something broken like a cam.
I dont think the euro heads, with euro valves is a non interference. I was building scots with devek cams, (slightly higher lift) and it wasnt by a good margin. .2". (at TDC, i could depress the valve only .3" before valve piston contact) since you are talking the same engine, this could be the same situation, even if you have euro cams which is only 1mm greater lift.
If something with the valve train is really jammed that could be it too.
are you sure the cam pulleys are aligned? I would loosen the belt , and remove it off the cam pulleys and see if you can rotate the engine.
If it is still stuck, you may have dropped a valve (unlikely) or siezed pistons.
you used different pistons in the block? how were the ring clearances? how were the piston clearances. same tollerance numbers block to pistons?
one more thing, on the clicking, was it click click click (fast as you can say it) or was it more of machine gun sound frequency like from an uzi? the reason i ask, if its lifter, the slower frequency is valve related (Or lifter) and the high frequency is piston, bearing, crank, etc, bottom end related.
mk
)one way to back the engine a bit, is to use a fat flat head screwdriver on the starter ring through the peak hole area. if it is jammed in both directions, it probably is block or crank related, especially if you can move it a few inches and its really stiff both ways. I hope that it is not, but the only thing in the valve train that can do what you describe is something broken like a cam.
I dont think the euro heads, with euro valves is a non interference. I was building scots with devek cams, (slightly higher lift) and it wasnt by a good margin. .2". (at TDC, i could depress the valve only .3" before valve piston contact) since you are talking the same engine, this could be the same situation, even if you have euro cams which is only 1mm greater lift.
If something with the valve train is really jammed that could be it too.
are you sure the cam pulleys are aligned? I would loosen the belt , and remove it off the cam pulleys and see if you can rotate the engine.
If it is still stuck, you may have dropped a valve (unlikely) or siezed pistons.
you used different pistons in the block? how were the ring clearances? how were the piston clearances. same tollerance numbers block to pistons?
one more thing, on the clicking, was it click click click (fast as you can say it) or was it more of machine gun sound frequency like from an uzi? the reason i ask, if its lifter, the slower frequency is valve related (Or lifter) and the high frequency is piston, bearing, crank, etc, bottom end related.
mk
12-15-2007, 02:31 PM
#10
Racer
Thread Starter
Here's the story on the first engine.
can you go over the original failure. how did the piston "break" and the rod bend? failed 2/6 bearing? Then, how did the head get damaged. what type of fix did you do on the heads?
The first engine I assembled started up right away but had a noticable clicking sound like a lifter clicking.
Yes, It smoked bad when cold, and during hard excelleration even after warm up. I think this could have been from a damaged oil ring. I'm not sure. I never could tell if it was the chicken or the egg.
The engine was a M28/12 block and crank with my M28/11 pistons and rods. Both blocks were tolerence group 1.
About 800 miles or so I had a valve break or a piston break. Again I'm not sure. But the end result was a broken #1 piston, bent rod, cracked block and broken exhaust valve the punched itself into the head about 1" deep. The head was repaired and resurfaced.
on the second rebuild. you got another M28-12 block? could there be clearnce issues with the crank and the block?
I am now reusing my early M28/11 block with the late M28/12 large journal crank and M28/11 euro S pistons. These are the same pistons that came from this block with the exception of #1 that was destroyed. I also replaced #6 with a nicer one as my original piston had alot of detonation damage on the top. Both replacement pistons are tolerence group #1 and both have a minus sign on the top. This is the same as my original pistons. Prior to installation of the cams the short block seemed to rotate smoothly.
smoke on the acceleration could be ring issues. did it run rough?
I agree, Yes, I was attempting to verify if the issue was a result of a tune up or internal when it failed.
as a note, that might not apply, with the newer, larger oiling hole crank, when used on the early block, there were some serious clearance issues that were easy to fix.
I read about your clearance issue and check my block to crank closely. I did not have that issue.
Mk
The first engine I assembled started up right away but had a noticable clicking sound like a lifter clicking.
Yes, It smoked bad when cold, and during hard excelleration even after warm up. I think this could have been from a damaged oil ring. I'm not sure. I never could tell if it was the chicken or the egg.
The engine was a M28/12 block and crank with my M28/11 pistons and rods. Both blocks were tolerence group 1.
About 800 miles or so I had a valve break or a piston break. Again I'm not sure. But the end result was a broken #1 piston, bent rod, cracked block and broken exhaust valve the punched itself into the head about 1" deep. The head was repaired and resurfaced.
on the second rebuild. you got another M28-12 block? could there be clearnce issues with the crank and the block?
I am now reusing my early M28/11 block with the late M28/12 large journal crank and M28/11 euro S pistons. These are the same pistons that came from this block with the exception of #1 that was destroyed. I also replaced #6 with a nicer one as my original piston had alot of detonation damage on the top. Both replacement pistons are tolerence group #1 and both have a minus sign on the top. This is the same as my original pistons. Prior to installation of the cams the short block seemed to rotate smoothly.
smoke on the acceleration could be ring issues. did it run rough?
I agree, Yes, I was attempting to verify if the issue was a result of a tune up or internal when it failed.
as a note, that might not apply, with the newer, larger oiling hole crank, when used on the early block, there were some serious clearance issues that were easy to fix.
I read about your clearance issue and check my block to crank closely. I did not have that issue.
Mk
12-15-2007, 02:37 PM
#11
Racer
Thread Starter
certainly possible. the shop working on scots original rebuild did this. we had a coil wire reversed and the guy kept on starting the engine. looking down the holes, you could see a puddle of fuel. this is one of the reason i like to use a mix of assembly lube (redline) and oil on the cylinders or pistons skirts, just as a precaution, and as i mentioned it probalby has very little risk to not breaking in the rings properly with Alusil bores. (contrary to Brendans textbook advice )
one way to back the engine a bit, is to use a fat flat head screwdriver on the starter ring through the peak hole area. if it is jammed in both directions, it probably is block or crank related, especially if you can move it a few inches and its really stiff both ways. I hope that it is not, but the only thing in the valve train that can do what you describe is something broken like a cam.
I dont think the euro heads, with euro valves is a non interference. I was building scots with devek cams, (slightly higher lift) and it wasnt by a good margin. .2". (at TDC, i could depress the valve only .3" before valve piston contact) since you are talking the same engine, this could be the same situation, even if you have euro cams which is only 1mm greater lift.
If something with the valve train is really jammed that could be it too.
are you sure the cam pulleys are aligned? I would loosen the belt , and remove it off the cam pulleys and see if you can rotate the engine.
If it is still stuck, you may have dropped a valve (unlikely) or siezed pistons.
you used different pistons in the block? how were the ring clearances? how were the piston clearances. same tollerance numbers block to pistons?
one more thing, on the clicking, was it click click click (fast as you can say it) or was it more of machine gun sound frequency like from an uzi? the reason i ask, if its lifter, the slower frequency is valve related (Or lifter) and the high frequency is piston, bearing, crank, etc, bottom end related.
mk
)one way to back the engine a bit, is to use a fat flat head screwdriver on the starter ring through the peak hole area. if it is jammed in both directions, it probably is block or crank related, especially if you can move it a few inches and its really stiff both ways. I hope that it is not, but the only thing in the valve train that can do what you describe is something broken like a cam.
I dont think the euro heads, with euro valves is a non interference. I was building scots with devek cams, (slightly higher lift) and it wasnt by a good margin. .2". (at TDC, i could depress the valve only .3" before valve piston contact) since you are talking the same engine, this could be the same situation, even if you have euro cams which is only 1mm greater lift.
If something with the valve train is really jammed that could be it too.
are you sure the cam pulleys are aligned? I would loosen the belt , and remove it off the cam pulleys and see if you can rotate the engine.
If it is still stuck, you may have dropped a valve (unlikely) or siezed pistons.
you used different pistons in the block? how were the ring clearances? how were the piston clearances. same tollerance numbers block to pistons?
one more thing, on the clicking, was it click click click (fast as you can say it) or was it more of machine gun sound frequency like from an uzi? the reason i ask, if its lifter, the slower frequency is valve related (Or lifter) and the high frequency is piston, bearing, crank, etc, bottom end related.
mk
12-15-2007, 04:02 PM
#13
Drifting
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Answer was
So we go back to "m8/12 is a non-interference motor"
Then the remaining possibilities are piston or crank related; I mean the pistons are too tight in the bore, there are 1 or more broken rings or the crank is bent.
I can not see there is a head related problem unless you used 32v heads or (as Mark said) a valve has dropped down below the normal point.
Marton
HTML Code:
Thanks, yes the balancer is installed as shown. I used my euro pistons for the build.
Then the remaining possibilities are piston or crank related; I mean the pistons are too tight in the bore, there are 1 or more broken rings or the crank is bent.
I can not see there is a head related problem unless you used 32v heads or (as Mark said) a valve has dropped down below the normal point.
Marton
12-15-2007, 04:39 PM
#14
Racer
Thread Starter
I went out and loosened the tensioner. The cams move, ( rocked a little) the crank doesn't. It's coming back out. I'll update you all when I figure this thing out. crap. It rotated fine before I put the cams on. I'm thinking when I flooded it the cylinder lube was washed but I'm not taking any chances.