Checking for timing chain stretch?

[starfiresx]

Hello all. just wondering what you think is the best way to check for timing chain stretch on my 94 K1500?

this truck has over 167,000 miles on it. 305cid. from what I can tell/ and from what the last owner told me it came from the dealer with a plow when purchased new. it also looks like nothing has ever been done to this engine.

I have been having some hesitating/missing problems with this truck lately. and I think I have it down to the EGR vale and solenoid. but I have noticed that when I did try to check/set the timing. it was jumping around a little. though the engine seems to run smooth at an idle.

set the timing at zero and the truck seems to be down on power. so that is why I ask about the chain. I think it is the chain or the outer ring on the damper has moved. or a combo of both.

what are your thoughts?

thanks Joe

[2000CAYukon]

I have a 90 K1500 with the 5.7. I am the original owner and it has 115K miles on it. I also noticed that the timing jumped around while setting the timing. I tore into the chain over the last thanksgiving weekend. I was amazed that the truck even was running. The chain was very sloppy. If the chain is original, it is probably loose and that is why you are seeing the timing jumping around.

//2000CAYukon

[MT-2500]

Put a socket and breaker bar on your crankshaft pulley bolt and move it back and forth and you can feel the slack in the timing chain.
Did you disable the set timing connector to set timing?
Anothe weak spot is the dist shaft bushing. If it gets to much side play it will run rough or miss.
MT

[starfiresx]

yes I did disconnect the set timing connector. also the distributor is new not rebuilt.

I tried that with the plugs in the engine after it was warm. and the bolt started coming lose. I will have to try with the plugs out.

thanks Joe

[jveik]

lol yeah when you sed it lost power at tdc (0 degrees) that would be expected, likely your engine is supposed to be timed at 4 to 8 degrees before tdc, which actually makes a pretty big difference.

[MT-2500]

Mr Mitchell on Demand says base timing is 0 degrees on all except the big boy 7.4 eng and it sets at 4 degrees before TDC.
Timing specs is usually on the underhood sticker.
MT

[starfiresx]

Well I warmed up the engine and pulled the plugs. took off the cap, and gave her a turn clockwise to make sure the chain was tight. turn it back counter clockwise and only had at the most 3 to 4 degrees of movement.
I don't seem to think that is all that bad! I was told by a friend that in 92 GM started using a true roller chain in the trucks. is this true?

I had to dive the truck today to pick up some equipment for my neighbor. the weird thing is my truck has this intermittent hesitation on take off, only when it is warm. and sometimes it takes off great with no hesitation.

Joe

[MT-2500]

Only 3-4 degrees slack is good.
Can not say what timing chain it has.
One thing to keep in mind after the eng is warm or hot is the egr valve opens when you first take off, To much or a to fast or sticking egr valve can cause a stumble or hesitation.
May not be the problem but one thing to check.
Also aftermarket egr valves somtimes do not work good.
Good Luck MT

[tykrz]

This is how to check:

1. take off distributor cap
2. mark the crank pulley and turn the pulley in one direction for about a quarter turn. then turn the pulley the opposite direction and note when the rotor in the distributor just starts to move. note how far you turned the crank pulley. if it rotated an inch then you're timing chain needs replacement.

One thing to keep in mind is that the GM 350's were notorious for having the rear cam lobes wear down. If you take it apart to replace the chain and sprockets you may want to consider replacing the cam while you're at it, especially if you have over 40000 miles on the engine.

[tykrz]

ps: If the damper has moved you will have a major vibration in the engine.