timing belt jumping time

[VR-4 fanatic]

Pardon if this issue has been addressed elsewhere, the newbie missed it.
I have a ’91 4G63 Galant VR-4 that has destroyed two heads (valves and pistons trying to occupy the same physical space) because the timing belt jumps three or four teeth on the crank pulley. Cams stay in time. Tension is correct. Thought THE problem had been identified with each rebuild. The rebuilt head ($500.00) is in hand however I am hesitant to install it without reasonable assurance the real issue has been corrected. One head had BC springs the other Super Tech Duals installed both had the same 280 cams. Built block and balance shafts are deleted.
History: Oil pressure sending unit leak, fixed. Tensioner bolt oil leak, fixed. Both leaks oil soaked timing belt, crank gear, and cam gear, everything. Under side of car will never rust. The timing area was wiped down after each oil leak fix and again prior to installing the second head. A non-OEM tensioner was installed on the first head replaced because the oil pump gear self destructed. Not sure that it actually collapsed, but…..it was replaced with an OEM unit that might have been compressed too quickly. All pulleys are new OEM parts. Reused the gates Kevlar timing belt after cleaning. Purchased another brand new OEM tensioner and replaced ACL rod bearings for second head install; let the reassembly sit overnight and checked the pin for correct tension. Completed assembly and drove to gas station, returned home, ate dinner, timing belt jumped timing on restart. Yes, the tensioner pin could be reinserted following the timing jump.
Possibilities: Cams are binding? Cam springs are too stiff (doubtful)? Bad OEM tensioner? Should not have reused Gates Belt? Clean entire area with brake cleaner and install new timing belt? Toss block and start over machining another block, new oil pump housing, and….?
Those are my thoughts. Ideas?

 

[92AWDHX40]

A lot going on in there pull it apart redo it something went wrong gates belt is ok, pulleys bad timing job?

 

[Dsmkauai]

It's either the tensioner not holding which I'm leaning more towards. Or the belt has stretched to much and you need to replace! Like I said it sounds like the tensioner isn't holding or set properly.

 

[BogusSVO]

The tensioner pulley, are you setting to the proper preload before pulling the pin?

I doubt the springs are an issue, unless both have been installed waaaaaay to tight and you are hitting spring bind.

 

[VR-4 fanatic]

Thank you for input. Timing spot on. Tension set with adjuster pin holes at 12 o'clock and tensioner pin moves without drag.

 

[92AWDHX40]

Make sure you get your timing tensioner correct, or youll have issues .

 

[VR-4 fanatic]

It's either the tensioner not holding which I'm leaning more towards. Or the belt has stretched to much and you need to replace! Like I said it sounds like the tensioner isn't holding or set properly.

Tensioner pulley bolt has correct torque. Belt stretch with kevlar belt minimal and correct tension should eliminate that issue.

The tensioner pulley, are you setting to the proper preload before pulling the pin?

I doubt the springs are an issue, unless both have been installed waaaaaay to tight and you are hitting spring bind.

Very frustrating to say the least. Preload is correct, timing correct, hydraulic tension pin has no drag, torque on tensioner pulley correct. Only thing I can come up with is some sort of cam binding and/or I didn't get the oil film cleaned up well enough.

This will be the third time around.

Appreciate your thoughts!

 

[Dsmkauai]

Rotate the motor around by hand clockwise and find what's causeing the problem! I've had to do this myself on customers cars that had timing issues. If you have all the covers off have someone rotate the crank while you watch do it until you see it jump or until you spot where its hanging up or becoming loose this should point you to your failure.

 

[BogusSVO]

Thank you for input. Timing spot on. Tension set with adjuster pin holes at 12 o'clock and tensioner pin moves without drag.

That is a bit off IIRC, they should be about 2 o'clock, and set to 24 in/lbs (?)

also rotated into the belt in a counter clock wise rotation.

 

[VR-4 fanatic]

Rotate the motor around by hand clockwise and find what's causeing the problem! I've had to do this myself on customers cars that had timing issues. If you have all the covers off have someone rotate the crank while you watch do it until you see it jump or until you spot where its hanging up or becoming loose this should point you to your failure.

Rotated multiple times to verify correct belt tension. Nothing unusual observed. That's why we let it sit overnight after setting timing. Rotated again prior to buttoning up and finishing install. Looks like we'll have to rotate a lot more. Could it be a combination of cam spring tension and oil residue on everything?

Thanks again.

 

[92AWDHX40]

Yes let it set I let mine sit but not overnight then I cranked her over 6 times to make sure It was all good, got mine right the first time, im mechanically inclined, very first big thing I did when my tb broke.

 

[Dsmkauai]

^ yes but the o.p. is having bigger problems than just setting timing bro! If you rotate counter clockwise do you see anything bind? You said it does it at start up right I think it jumped when you shut it off and the motor kicks back alittle then at startup it catches off! This is a problem with your tensioner not holding right l can almost guarantee a new oem one will fix this problem. That's if it's what is happening could be something else all together! If you can rotate the motor without problems over and over what else could it be but the tensioner or maybe tensioner arm is bent alittle.

 

[delta448]

Did you possibly over or under-torque the tensioner pulley's offset center bolt?
Does the auto-tensioner's rod extend anything other than 12mm when not installed?

I would start over with a new belt and a new auto-tensioner. Remember that oil and or any solvents can damage the timing belt.

 

[bryanwheat]

If the tension is set properly and you have a good tensioner than it is basically impossible for the belt to jump time. There just isn't enough slack for it to happen.

 

[95GSTowner]

The fact that u were able to insert the pin back in the tensioner after it jumped time makes me think it's a binding/interference issue. Did u check the t-belt for marks? Oil pan bolts on timing side too long? Also i see u deleted balance shafts so did u keep the balance shaft spocket or use a spacer? Sorry if sound crazy, im just trying to cover some of the issues i've seen

Lastly, did you have the timing covers installed? Im sure u do but im just asking

 

[VR-4 fanatic]

If the tension is set properly and you have a good tensioner than it is basically impossible for the belt to jump time. There just isn't enough slack for it to happen.

Well, that's what I thought too. I have been the 'after' market tensioner. This was an OEM unit. Torque on concentric bolt correct. The ONLY thing that makes any sense is oil residue on belt and gear or binding somewhere. The most likely somewhere is the 280 cams. So I am going to install the head with cams but no lifters to see if there is some binding. I am sure that the cam caps were not swapped in error with one of the other heads.

The fact that u were able to insert the pin back in the tensioner after it jumped time makes me think it's a binding/interference issue. Did u check the t-belt for marks? Oil pan bolts on timing side too long? Also i see u deleted balance shafts so did u keep the balance shaft spocket or use a spacer? Sorry if sound crazy, im just trying to cover some of the issues i've seen

Lastly, did you have the timing covers installed? Im sure u do but im just asking

Binding issue very possible. No marks on t-belt. Oil pan bolts correct. Two short under timing belt. Used a spacer wondering if we need to reinstall the gear????
NOBODY is crazy! Well, I am going that way! Two heads trashed and number three standing in the door. There is something going on here but so far nothing obvious.

Did you possibly over or under-torque the tensioner pulley's offset center bolt?
Does the auto-tensioner's rod extend anything other than 12mm when not installed?

I would start over with a new belt and a new auto-tensioner. Remember that oil and or any solvents can damage the timing belt.

Good question. Torque was set correctly. I'll have to check the 12mm measurement. Really don't want to pull pin and have to compress and reinsert pin. That apparently trashed one OEM tensioner because I compressed it too quickly even though I took my time.

Don't know about tensioner arm being bent. Looks OKAY but I can swap it out with one off the bench. At this point I willing to try just about anything and check and double check everything. But double checking hasn't uncovered anything obvious.

 

[pauleyman]

Oil pump trashed and binding? Bent crank plate?

 

[VR-4 fanatic]

Oil pump trashed and binding? Bent crank plate?

Oil pump spins freely. Yes, I had the oil pump gear eat itself and an earlier oil pump cover. This is a new OEM oil pump cover and the oil pump gear on this instal spin freely. New timing belt will be used on this install. Crank plate looks good and it was installed correctly. I am considering replacing the current spacer with the gear used to drive the front balance shaft (removed).



I appreciate your thoughts. Thank you.

That is a bit off IIRC, they should be about 2 o'clock, and set to 24 in/lbs (?)

also rotated into the belt in a counter clock wise rotation.

No I have not rotated the assembled motor counter clock wise. Concentric bolt was torqued to spec and concentric pulley was loaded to allow hydraulic tensioner pin to move freely. Assembly was hand rotated thru full cycle TDC to TDC multiple times and pin remained free. Concentric bolt was at correct torque after belt slipped.
I don't like the idea of leaving the timing belt cover off to observe running engine. Probable wouldn't be able to avoid another "ah shit" moment anyway.

What are we missing?

 

[VR-4 fanatic]

Resolved. Cleaned entire timing area with brake cleaner and installed rebuilt head new tensioner and new timing belt. IT LIVES!