This is in reference to my earlier post on the serpentine belt that killed my B6304 (see post id=498946). I got the ALLDATA information on this engine for both the timing belt replacement procedure and the Head R&R.

I have pulled the plugs, (Good Bosch Platinums) and removed the front covers, serpentine belt tensioner, and then checked the timing. I can get both the top pullies to line up with their marks right away, but the crank was 18 teeth off from where they lined up. Looks like the belt jump was on the crank.

I pulled the tensioner off and reset the timing according to the marks, but I still have interference when trying to rotate the engine. (this existed before I moved anything!) What has me stumped right now is that the #1 piston is not all the way to the top when all the marks line up. I don’t know if they are supposed to be or not though.

In the ALLDATA print out it shows a special tool that is inserted into the block after removing the starter that locks the engine in the proper position for setting the timing. It describe the process this way:

Align timing mark on crankshaft,

Remove starter motor,

Remove protective plug

Mount crankshaft locking tool # 999 5451 or equivalent

Turn crankshaft counterclockwise until stopped by tool

The notch that I am lining up on the crank is a very very small notch in the toothed gear on the rear top of one tooth. I am wondering if the problem could be in some way that this gear could have "slipped" or rung off a woodrif key so that the mark is no longer valid. It is appropriate to note that the engine locks up at the very same points now as it did before attempting this timing reset. Most likely it is at TDC on some of the cylinders.

Needless to say, the pistons are hitting something , (one of 24 somethings I think) but I sure would like to know that I was on the mark before tearing down the engine. So the big questions of the day are:

When the timing mark on the crank is lined up, is #1 on TDC? Or is this some arbitrary mark used only for process of setting the timing?

Also, how important is it to have the special tool # 999 5451? And what would a home made one look like?

Well when I broke the timing belt and with the cam cover removed, it was very appartent on the number of valves bent by looking at the lifters. All the lifters that were not at the closed position for the valve had bent valves. In all 12 valves were bent 10 exhaust and two intake. When I took the head off, scars on the pistons and I don't know if there is other damage(such as a bent connecting rods) that can't be seen unless the piston is removed. If the timing belt breaks or slips off you will bend valves even if the engine is at idle. Sorry to sound so pessimistic.

Clearly some damage will occur regardless of the speed or condition, but I've been told that a low speed failure, perhaps less than 20 mph will be less catastrophic, even relatively minor, than one at high speed. This makes intuitive sense, but frankly, I don't want to test the hypothesis....
--
John Shatzer, '92 965 @100K; one of a few still in captivity.

zach, check the the alternator or serpentine-belt tensioner (still don't know the right vocabulary)... it could be that a worn-out tensioner caused the belt to move sideways over the wheels and then shred, and then slam into the casing of the timing-belt. i was luckily in time to fix the problem. give me some feedback, ok?

uturn. 1992-965, 225.000km.

The crankshaft locking tool (and removing starter procedure) is only needed when resetting the timing gear to cam calibration. The two gears have an adjustment possibility used by loosening the three insex screws holding each gear (DON'T do this before carefully marking the screw positions at each gear) and turning the gear. This adjustment should be performed with the crankshaft locked and cams locked by another special tool. Made once in the factory, the adjustment never should need resetting. The gears rarely get loose or out of adjustment by themselves. I've used the crankshaft locking tool and it lined up close to perfect with the notches of the crank gear/oil pump housing in front.

For timing belt alignment, you never use any of the special tools - just line up the marks and you should be fine. I think you're right about TDC - the engine is not at 0 deg when positioned correctly for timing belt setup, look at the timing scale on the cam gear cover - but not sure, it was a too long time since I looked into that subject.

A broken belt unfortunately is almost guaranteed to destroy at least a few valves and probably other parts also. Look for a shop with "peep hole equipment" and look through the spark plug holes if you still need to be perfectly sure about the damages.

A warning also seems to be needed when engine work is considered on these machines: make sure your shop is reputable and skilled with the technology used to replace the engine head. They can give you a never ending problem if not. If pistons or cylinder walls are damaged - look for a replacement engine instead.

/Martin
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65' 121, 73' 165