83 Cab QV - Timing Belt broken, again...

Disclaimer: I've never had a broke belt on the Ferrari 8 cyl engine. Now, I have replaced the belt on 8 jobs, and so far zero failures. The timing belt tensioning system on the Ferrari is one of the old style. It uses a spring to set the pre-load on the belt to a specific tension, and then a lock nut is used to maintain that tension constantly. There is no hydraulic or belden washer stack to allow for engine growth and contraction.

If the situation were that timing belt was installed at a cold temp, and you were using it at a hot temp the belt may have stretched beyond it's life. Another failure mode is that the spring that pre-tensions the belt could be out of spec and putting too much tension on it from the start. Both of these would lead to a failed belt as there is no running adjustment.

I doubt the short oil deprivation caused any issue. Since you were able to start and run the engine with oil pressure after the starvation, that indicates that lubrication was still working, unless the cam seized and you won't be able to tell that until you rotate the cams by hand.

If it's the rear bank, the job can be done in the car provided you didn't hole a piston. It's rare to have a piston holed. This little engine will go well over 100k miles before needing to refresh the bearings and rings. I would evaluate the situation before deciding to rebuild the whole thing as you might be introducing more problems than you fix with potential infant mortality.

At a minimum, you'll want to check the cam tension springs for spec, and insure the balance of the cam drive gears and rollers are good. Change to the new style roller and maybe just replace the tension spring might be ok. I'll be in Houston this wknd if you want me to have a look at it. PM me with your contact info and we can go from there.

I have an 83 cab QV with 100k miles.

 

It be interesting to see which belts broke and how?
I just finished my belt replacement and the only area that I see would fail would be a loosen tensioner bolt, collapse tensioner, broken cam pulley, rather hard to break the belts unless you shear it off, especially with only 5k miles on them. Was the car parked in a garage or mostly subjected to extreme hot temperatures, if so it probably would shorten the life of the belts and bearings I would think. Also, wondering if it was HIll Engineering tensioners or not that you have on your car. I hear its the best so I used it on mine.

Please post your findings.

best
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Yes, the 308/Mondial engine does have a tendency to lose oil pressure in hard right-hand turns. This is something that has been discussed on this site in other threads, and those of us who have done autocross or track events with these cars know the problem all to well. If you search through old threads, you will see that there is a baffle available that you can install in the oil sump that will prevent this from happening. Since you are going to be opening the engine up anyway, you might want to consider getting one and installing it in the sump.

That said, I don't see that a momentary loss of oil pressure would cause a timing belt to break, especially more than 30 minutes of driving after the loss of pressure occurred. You really need to have someone take a good look at what is going on with that engine. It is possible that something was not set up right, or something is rubbing against the belt and causing it to fray or wear. You need to know if this happened on the same bank as the earlier belt failure. If so, I'd be suspicious that there is something other than a loss of oil pressure in a hard turn going on here.

Sounds like you need a really good Ferrari mechanic. I'd suggest talking to BigTex. He's down your way and can head you in the right direction.

 

Just curious, how did the belt fail? (e.g. stripped teeth, lengthwise split, something else?)

The PO of my QV was astonished to see the air pump on my car with a seized shaft, drive pulley off the cam was stationary with the cam spinning underneath it, if I remember right. Seems something like that has the potential to strip teeth if the shear pin doesn't fail like it's supposed to. (This sounds completely unlike your problem though.)

My guess right now is that it could be a problem is alignment somewhere in the path the belt takes, and it's abrading on one side or subject to a twisting force. I would think something like that would be very obvious, though. I would certainly inspect everything the belt runs over for run-out and axial play.

Certainly strange to see this crop up twice is rapid succession.

 

I had the forward bank belt strip (dry rot/age) on my 3.0 QV Coupe and there was no damage. I fixed it and Birdman put a whole lot more miles on it.

Now, my t Coupe might not be so lucky...

 

Valve damage is almost a certainty
That head needs to be pulled

 

Easy to check for valve damage by pulling the valve cover. If the adjustments are crazy out of whack its because a valve can't close due to being bent. Just one way to check.

Not 100% conclusive but if your gap is 5 to 10 times what it should be it's a strong indicator.

Good luck with it.

 

Did you ever find the cause of broken belt? I just had the same thing happen. There saying belt broke because cam seized up because of oil starvation.

 

Mine should be opened in the next week. Sending heads to the machine shop. I also was turning into a street when heard the belt making a funny sound then it broke then the ticking sound. I drove less than a mile home baby it all the way.

 

The motors is out of the car and the belt was broke. My mechanic was surprised it still runs. Just one belt was broke and it still starts right up. He thinks it is an oil issue. The one cam on right won't turn. The other does turn.

 

Closest to the rear bumper. So I assume its the back.

 

Here's a pic.

 

Let me help you guys out by posting an 83 Mondial engine out photo so all can follow what you are saying. So the rear facing belts broke due to oil starvation which lead to the cam rod locking up causing the belts to break ? Possible but I've never heard of this.
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Hi Gents, just a thought here, if the camshaft seized up due to oil starvation surely there would be evidence of this ie pickup on the camshaft in question.
As ohers have said here, it seems odd that a momentary loss off oil pressure would cause a failure so quickly.
Anyway it will be interesting to see if there is any rotational scoring on the camshafts and the head and camshaft caps, photos would be good also for us all to see.

 

Interesting about the oil pressure theory.

Does anyone know what is the correct oil pressure readings on the dial when hot and cold?

Not sure if it washes between the 4 Mondial variants?

 

Not sure about all 4 Mondial models but here is what the manual for the 3.2 says about oil pressure:
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5K miles on a belt makes me feel icky!!!
I don't care about the time. Must be some
serious other factors.