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Discussion Starter · #1 · (Edited)
So recently my 1991S had developed some rod knock. Just before I got a very generous offer for a parts car with a recently rebuilt engine. Only issue was that it sat for 9 years.
My plan was to assess that engine and swap it with my engine while I rebuilt mine. Used my gearbox, flywheel, clutch, injectors, etc.
After letting the engine soak with ATF and MMO down the plug holes for some days I checked the compression and it was good.
Pulled the engine and installed a Centerline mechanical tensioner, thermostat, water pump, timing belt etc. and put all in the car. Ran perfectly until the first time I took it up to close to redline. I heard a bang and the car immediately lost compression.
Once I got home I checked the timing belt. It was still tight but off by 2.5 cogs or so on both cams. Exactly the same. Only other symptom of note is that both of the plastic cam end covers had come out of their receptacles. Correcting the timing and further investigation showed that all the intake valves are leaking So it slipped the belt. Am trying to understand why.
Made sure that I installed the centerline tensioner very carefully and erred on it being at the tight end of their spec. When the engine failed I distinctly heard something hit the road and was wondering if a valve had dropped or a piston crown had separated, ejecting debris. The engine, superficially looks undamaged however.
Have yet to pull the heads but all the valves are present and appear whole and none are sticking if not seating. None of the plugs are damaged and what I can see of the pistons look ok. My current best theory is that I may have allowed something to remain in the engine compartment that interfered with the belt. then getting ejected onto the road. Have gone back and not found anything on the road. A problem with that theory is that the belt has no damage, and the crank and cam pulleys appear undamaged.
Engine rotates just fine now other than having no compression. No issues with the clutch and I did not find any problems with the CV joints, or any final drive stuff. I am planning to put a 3rd engine I have lying around in the car for now and hope to use the tensioner again but until I have a decent working hypothesis on what happened I am not too excited by that. Clearly I need to pull the heads but am curious if anyone else has experienced anything like this.
 

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2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
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Ugh. Sorry to hear of this.

One question, were all of the lower plastic belt covers installed at the time? I had the ones on my 91S finally crack and start to fall apart, if nothing else rubbing against the serp belt, forcing it to one side, almost coming off at the pulleys. Had to completely remove those and buy some used but intact replacements. Have to get them installed.

Possible you had a piece of gravel, or whatever, get tossed up to the belt as it rides on the crank pulley, making it jump a couple of teeth? The observation that the timing was "off by 2.5 cogs or so on both cams" indicates that the belt most likely did jump at the crank.

As an afterthought, one way to confirm something like this happening would be to put indication marks on the timing belt to match marks on the cam pulleys. That would be another way one would know which of the three pulleys was involved with a belt jump.

Or, is this a mark against the Centerline replacement tensioner? Maybe warping and relaxing somehow at high rpm and then returning back tight at lower rpms? I have yet to feel that I could trust that tensioner, sticking with the OEM original as installed. But, who knows. I certainly don't.

BTW, very minor point, but paragraphs would make your posting easier to read. Helps to understand what you've got. No biggie otherwise, lol.

Once again, sorry to hear this, esp since I also drive a 91S as my DD.
 

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Discussion Starter · #3 ·
Del,

Thanks for the ideas and appreciate the feedback on my stream of consciousness post. Was trying to capture everything and before I knew it things had got out of control.
Had all the belt covers on. Had not yet installed the fender covers.
Agreed on the crank being the pulley that jumped. It is hard to tell but the initial symptom definitely felt like some kind of interference. Whether that was the initial valve contact or something else I do not know yet.
Really hate to point any fingers at the tensioner. It is far more likely I did something silly but sure would like to know what. Their instructions are very simple and after having a spring break on another tensioner I decided to go with the centerline product. Really hope that is not the issue. Anyway, more to come.
 

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2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
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If nothing else, does demonstrate just how strong the new timing belts are. My feeling is that they are so reliable, worrying about them falling apart or stretching shouldn't be much of a concern these days.

Maybe the tensioner did bend a little under such a high load caused by a foreign object stuck between the crank pulley and belt, thus saving the belt, and then springing back to pretty much it's original tension setting.
 

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A long time ago in a life far far away I once had a belt skip on a 1300 x1/9 engine after a bunch of work and it ended up being a worn crank pulley. I don’t know what the criteria would be on the 164.
 
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Not too familiar with your car but does your computer shut down the engine at redline? My porsche 944 turbo does. What I am getting at is maybe your tach is off and you went past redline and floated your valves and bent some is why no compression now and what you heard could be valves hitting pistons.
 

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2015 Chevy (Holden) SS, 1989 Milano (Shankle Sport), 1991 164S
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Yes, rev limiters.

Trouble is, the timing ended skipping off ~2.5 teeth, evidently enough to bend valves. That most likely would not occur from just plain overrevving but belt skipping.
 

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Well I was thinking that if no rev limiter then I would think that valves hitting pistons could cause timing belt skip along with bent valves is what I was thinking of.
 

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Wow that stinks. Sounds like something got kicked up from the road. I know the Alfa mechanical tensioner is not the favorite but I have been running them long time, the preferred tensioner for three different top end mechanical shops who had the choice between the hydraulic, mechanical or fixed tensioner. Seems unlikely that the centerline tensioner is the cause of your problem. If the fender guards are not installed seems more likely for debris thrown up with the transverse engine? Another possibility is that one of the valve springs is not good, perhaps taking a set after 9 years of sitting. Presuming you pulled the valve covers before installing the engine and checked all the clearances but a bad spring would pass visual inspection. You would have to over-rev pretty far on a good engine to float a valve.
 

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I tend to agree.

Have you ever looked at the upper surface of the lower suspension arms? They often get covered in dirt and gravel, just from driving around for many miles. It can be a little shocking. I believe in all the fender panels being on, as well as the lower belt covers of which there are three, but since the fender covers can be a pain sometimes to reinstall, it is always tempting to leave them off. I always put up with the effort to make sure they are on.

A couple are trimmed back up behind the strut just a very little to make it easier, but not down low.
 

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Discussion Starter · #11 ·
Thanks all. My car is not exactly a garage queen but especially with this engine install, and newly rebuilt steering rack I made sure things were pretty clean.
This was my second test drive hence why I had not reinstalled the fender guards. I was definitely at higher revs but nowhere near valve float territory.
At this stage I am going to pull the heads and probably the oil pan to make sure nothing else is a amiss.
On the tensioner, centerline instructions are that the belt should "twist" flex between 75 and 90 degrees on the longest part of the belt. I compared this to how tight the regular, spring loaded, tensioner was and tightened until I could, with effort, twist it to 90 degrees. This may have been too loose. Just have a hard time imagining why it would slip at revs that I gradually approached as I accelerated the car in second gear. Also when I checked afterward it had the same degree of tension. Still a mystery.
 

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Weird.
 

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If something went through the belt to make it jump, a piece of plastic, stone or nut, you will see damage on the belt when you remove and inspect it. Might solve the why question...
 

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You would think, even with the superior design and materials of these belts.
 

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Maybe the OP is yet to remove the belt and inspect but yes I can assure the OP if something has gone under the crank there will be a tell tail.
 

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Discussion Starter · #16 ·
Belt is in perfect condition and no indication of any damage to any of the pulleys or and no wear on the back of the belt. Thank you Alfettaparts2 for the comment about there would be damage to the belt. The fact that it felt like something broke, and that I distinctly heard something hit the road behind me, (not found), indicates to me that I have yet to find a reasonable explanation and perhaps more will be revealed when I get the heads off.

Does anyone know if the exhaust valves are intereference by the way? They appear to not be leaking air but I will probably have to confirm on the bench as the intakes definitely are.

I have been making a video of the project and the screen grab shows how far they slipped. (rear cam had the same relative clocking) I confirmed that the car was at TDC on cylinder 1 when I checked because I was unsure how far things had gone at the time.
 

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I have no comment, but interested in what you find, hence this post so I can follow your thread. Best of luck

BTW: Has anybody done any calculations to see how much hp or torque would be lost if these engines were modified to not be an interference engine (i.e. pistons have deep enough valve pockets that no valves would ever hit)? Honestly if it's like 10 hp ... surely a modification well worth making?
Pete
 

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It would be a long shot but maybe your woodruff key sheared at the crank pulley? Assuming the crank pulley is indexed with a key way....
 

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Discussion Starter · #19 ·
It would be a long shot but maybe your woodruff key sheared at the crank pulley? Assuming the crank pulley is indexed with a key way....
Wow, did not think of that. I think it is unlikely given just how tight that nut is but I will check with a dial indicator to make sure TDC is where it should be.
 

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Discussion Starter · #20 · (Edited)
Heads are off. Have to get to a hardware store to make my liner securing tool so I have not rotated the engine but the only damage I have found at all is the bent intake valves. No damage to the pistons that I can see, bores are good on the ones I can see. At this point Occam's razor says that I failed to tighten the Centerline tensioner enough. Not sure how that makes me feel. Glad that I did not have a good engine grenade on me. Bad that I did not get the belt tight enough apparently. Thought I followed directions carefully, tightened, rotated engine a couple of times checked again. Compared it to the tension on the engine that was out of the car. I have definitely had Lancia timing belts looser than it was. If it is the case then I think Centerline needs to modify their twist deflection instructions.

It may be that a mechanical tensioner needs to be tighter cold than one that is spring loaded. If I use it again I will definitely leave the cam belt covers off and check it hot .
 
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