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I am having a vibration problem sitting still in neutral and when i rev up to higher rpm as well. It never goes away. Could it be an incorrect flywheel ? What is the correct flywheel for a 1970 454 What do you think, any suggestions are appreciated. Thanks
Had a couple BBC but never owned a 454. But I vagally remember when the 454 was introduced to the Chevy lineup. It seems there was an issue with balancing even way back when. GM engineers insisted on balancing the 454s vibration damper, crank & flywheel together as one unit before installing it into the block.
Evidently, the 454 harmonic balancer has a specific weight on the inside of the hub. Hard to spot, but visible.
You can feel the extra size of the weight on the inside back of the front balancer with your finger, and you can see the added weight on the flywheel if you pull the inspection cover off and rotate the engine.
Verify both are there.
Most likely is some dummy replaced the clutch/flywheel at some point and used the wrong part. Or the balancer failed and the wrong part got put on.
Now depending on how original you think the car/engine is, or if it is a high performance build, it could also have been subject to an expensive high performance crank balancing job with mallory metal which would mean it is now internally balanced. It's unlikely, but you could see the mallory metal thru a borescope thru the oil pan hole.
Either way, get it wrong, and it will vibrate, and likely fail.
This is not a factory balancer, but it is a clear pic of how much extra metal should be on the backside of the front crank balancer. So you know what to "feel" for.
More info on original parts 3993827 1970-90 14" 3.58" 11" 168 Counterweighted for externally balanced Mark IV 454 engines. Use with balancer P/N 3963530.
yes, the 454 is externally balanced by a special flywheel and front damper that will not work on other big blocks that are internally balanced, it it get worse as you rev, then you probably have the wrong flywheel or balancer.. or both. see the above pics for what you need.
unless it is not a 454 and is a a 427... a 427 with a 454 balancer or flywheel will cause vibration issues also..
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I went through a similar issue last summer but it wasnt a 454.
Do as directed above insuring the appropriate weights are installed. Aftermarket flywheels and dampers have removable weights.
Check the motor and transmission mounts. IF you see the motor move when you give quickly give it gas then you should replace the mounts. I went to solid mounts because my High Energy Poly mounts all failed
Make sure all the bolts are tight.
Make sure its a 454 as noted by Joe...either check the stamp or you will have to drop the pan and check the crank.
Last edited by Rescue Rogers; Apr 16, 2022 at 08:09 AM.
you may be able to spot crank casting number with a borescope through the oil drain hole. or possibly piston number either on skirt or on top of piston thru spark plug. i doubt trying to measure piston travel using a coat hanger or similar thru plug hole will be able to accurately see the 1/4 inch stroke diff.
Flywheel issues
