Possible timing chain issue?
Thread Starter
Drifting
Joined: Oct 2020
Posts: 1,568
Likes: 578
From: Wisconsin
Possible timing chain issue?
My new-to-me ‘71 has a GM Performance 350/290 hp crate engine.
I have the receipts and specs on the motor showing it was installed in 2017. I know from the registry the car had 60,xxx miles in 2016, it now has 64,xxx miles. So that tells me the motor has less than 4,000 miles.
I’ve been doing a little tuning on it because it doesn’t seem to run quite right. It has misses all through the rpm range. I have to advance the timing a lot to get it to run halfway smooth.
I verified the TDC mark on the balancer is pretty accurate. However, as I was turning the crank back and forth finding TDC, I noticed quite a bit of crank movement before the distributor rotor would turn, like 15+ degrees of crank movement.
Now I know it’s possible that the timing chain can be stretched or worn out, but it seems strange in only 4K miles.
Anyone else have a similar occurrence?
I have the receipts and specs on the motor showing it was installed in 2017. I know from the registry the car had 60,xxx miles in 2016, it now has 64,xxx miles. So that tells me the motor has less than 4,000 miles.
I’ve been doing a little tuning on it because it doesn’t seem to run quite right. It has misses all through the rpm range. I have to advance the timing a lot to get it to run halfway smooth.
I verified the TDC mark on the balancer is pretty accurate. However, as I was turning the crank back and forth finding TDC, I noticed quite a bit of crank movement before the distributor rotor would turn, like 15+ degrees of crank movement.
Now I know it’s possible that the timing chain can be stretched or worn out, but it seems strange in only 4K miles.
Anyone else have a similar occurrence?
2026 Loser of the Year
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From: New Or-leens Loo-z-anna
I just found this info......
Three to five degrees is normal, and more than 10 degrees is excessive. More than 10 degrees of slack indicates that it is time to replace the chain and gears.
Three to five degrees is normal, and more than 10 degrees is excessive. More than 10 degrees of slack indicates that it is time to replace the chain and gears.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
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just becausse they rebuilt the motor doesnt mean they changed the chain or did the job correctly. Are you spinning the motor by the bolt or the balancer? Are you sure the harmonic balancer isnt spinning?. The motor I just picked up had a sheared key on the balancer shaft.
To replace the chain you will need a new timing chain gasket, water pump gasakets and possibly a new pan gasket as well. You should be able to do it in the car by dropping the steering arms to get clearance
To replace the chain you will need a new timing chain gasket, water pump gasakets and possibly a new pan gasket as well. You should be able to do it in the car by dropping the steering arms to get clearance
Thread Starter
Drifting
Joined: Oct 2020
Posts: 1,568
Likes: 578
From: Wisconsin
just becausse they rebuilt the motor doesnt mean they changed the chain or did the job correctly. Are you spinning the motor by the bolt or the balancer? Are you sure the harmonic balancer isnt spinning?. The motor I just picked up had a sheared key on the balancer shaft.
To replace the chain you will need a new timing chain gasket, water pump gasakets and possibly a new pan gasket as well. You should be able to do it in the car by dropping the steering arms to get clearance
To replace the chain you will need a new timing chain gasket, water pump gasakets and possibly a new pan gasket as well. You should be able to do it in the car by dropping the steering arms to get clearance
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,259
Likes: 9,401
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Yes a single roller isn't a high performance chain and 4000 miles isn't even nto oil change time for the new oils....too bad that some companies will put poor equipment in their motors and put their name on it. Have you contacted them about the chain?
Melting Slicks
Joined: Dec 2009
Posts: 3,235
Likes: 658
From: Thunder Bay
While you have the distributor out check the end play. It's hard to imagine someone built an engine without installing a new timing chain, but it's not hard to imagine someone not setting the endplay on the distributor. It's also a LOT easier to check.
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Le Mans Master
Joined: Apr 2011
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From: Hermosa
Another possible cause is if the block was line bored and a lot of material was taken then the distance from the crank center to the cam center is reduced. This will make the (stock length) timing chain looser than normal creating a lag in the rotor when turning from one direction to the other.
little story on that information fi you're not familiar with line boring.
https://www.hotrod.com/articles/ccrp...g-distributor/
little story on that information fi you're not familiar with line boring.
https://www.hotrod.com/articles/ccrp...g-distributor/
Last edited by REELAV8R; Apr 9, 2021 at 03:45 PM.
