Timing chain slop?

[Bonnewagon]

Has anyone ever measured the amount of crankshaft degrees that is acceptable for timing chain slop? If you put a socket on the crank nut you can turn the crank a little before you feel the chain tighten against the camshaft gear. I know when it is new there is no slop but even a week of running will stretch it a bit. So when does the slop become unacceptable? How many crankshaft degrees of turning back and forth constitute a bad chain? This on a Pontiac 400 but most standard V-8's use the same set up. I feel this chain is so bad it is retarding the cam timing. Without mounting a degree wheel I estimate this crank can turn about 45 degrees in either direction. Seems excessive.

 

[airboatgreg]

45 degrees? No way. 4 or five degrees I wouldn't worry about

 

[L92 OLDS]

Great question. It seems all of my Oldsmobile engines had timing chain slop almost immediately

 

[olds307 and 403]

Great question. It seems all of my Oldsmobile engines had timing chain slop almost immediately

Found the same thing, the Cloyes Street Roller was loose to start with, looked bad after a few miles, only 1.5 on the balancer, no issues. The billet Cloyes set is much better out of box. I was told 4 degrees maximum.

 

[lilbowtie]

I run nothing but billet sets for that reason - change it before you have bigger problems, pontiacs aren't bad.


There is a very simple check for a loose timing chain due to a broken tensioner, worn gears, or a stretched chain. Pull the distributor cap and observe the rotor position. Take a breaker bar and a appropriate socket and put it on the crankshaft damper pulley. If you have a degree wheel put it on the damper pulley else you can just chalk mark the timing mark position at the appropriate time.
Now - slowly turn the crankshaft pulley in a clockwise direction. Watch the distributor and observe that the rotor is moving. Stop turning. Now - mark the damper pulley position with the chalk or observe the degree wheel. Very carefully turn the crankshaft in the other direction and VERY carefully observe the rotor in the distributor. The instant it begins to move STOP turning and mark the crankshaft position again. Measure the number of degrees of rotation of the crankshaft. If there is a lot of slop in the chain then you will have moved the crankshaft ten or fifteen degrees (or more) before taking the slop out of the chain after the reversal before the camshaft began to turn. Get the picture?? If all is well and there is no slack in the timing chain then you will see about three to five degrees of "reverse motion" before the distributor begins to turn.
If you are not sure how many degrees it turned during the procedure there is a simple way to calculate that based on the spacing between the chalk marks. Take a string and wrap it around the crankshaft damper where you made the chalk marks to measure the circumference of the damper. Let's say it was 18 inches. If there is one inch between the chalk marks then divide 1 by 18 and multiply the result by 360 (the number of degrees in a circle). In this case the answer is 20 degrees and it is time to replace the gears!!!

 

[motorheadmike]

This is why I kept the tensioner in my Procharged LS2 even with the new chain. Beats chasing wear as things fall out of spec.

 

[Bonnewagon]

Thanks! That is what I feared. 20 degrees is too much? Yikes, I'm surprised this thing didn't jump a tooth yet. I just didn't want to open the timing cover if it was not due. I have a Cloyes on order just in case so I guess it will go right to work. By the way, I had a closeout sale email from RockAuto and the Cloyes Pontiac chain was in it. They had 3 left so I bought them all.