Vibrations after stroker build
06-21-2008, 07:37 PM
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Vibrations after stroker build Looking for some suggestions here as I am not quite sure what is going on with my new engine...
Recently replaced my old engine with a neutral-balanced 383 stroker built using forged Eagle crank / SRP pistons etc... When I made the purchase, I paid extra to get the rotating assembly balanced; as such, I assumed they did a good job so we didn't double-check the balance prior to installing these items. The flywheel and the clutch have also been neutrally balanced, and I am using a Fluidampr for good measure. We went with poly engine mounts for this build, and for what it is worth, the car is a six-speed.
After all this, I have a noticable vibration between around 2000 - 2500 rpm that can be felt through the shifter and also rattles the dash around a little bit. The vibrations only occur when the engine is under load and not when I take my foot off the gas. In addition, the vibrations seem to get worse once the engine warms up and the car goes into closed-loop. Since everything has been neutrally balanced, I am kind of at a loss for what might be causing the vibrations. Could the poly-mounts be doing this? Any suggestions are welcome. Thanks.
Recently replaced my old engine with a neutral-balanced 383 stroker built using forged Eagle crank / SRP pistons etc... When I made the purchase, I paid extra to get the rotating assembly balanced; as such, I assumed they did a good job so we didn't double-check the balance prior to installing these items. The flywheel and the clutch have also been neutrally balanced, and I am using a Fluidampr for good measure. We went with poly engine mounts for this build, and for what it is worth, the car is a six-speed.
After all this, I have a noticable vibration between around 2000 - 2500 rpm that can be felt through the shifter and also rattles the dash around a little bit. The vibrations only occur when the engine is under load and not when I take my foot off the gas. In addition, the vibrations seem to get worse once the engine warms up and the car goes into closed-loop. Since everything has been neutrally balanced, I am kind of at a loss for what might be causing the vibrations. Could the poly-mounts be doing this? Any suggestions are welcome. Thanks.
07-02-2008, 08:27 PM
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Actually, the more I drive the car, the more I am starting to think that what I am calling vibrations are more like rapid pulsations that travel through the car. It is almost as if the car is missing radidly; it actually shakes the dashboard around and you can feel it very strongly through the shifter but not through the steering wheel. Since it only happens when the engine is under load and when the car is in closed-loop, I am starting to think it may have to do with the tune? Do you guys think this is possible?
07-02-2008, 08:54 PM
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the 383 cranks come neutrally balanced. and are balanced to some extent. however, if your running the factory lt1 balancer, (its internally balanced). and the flywheel should be external from factory. due to the lt1 block being 1 piece rear main. if your running the factory balancer you'll hafta have mallory metal added to crank during balancing. when i did my first 383 build years ago, the crank manufacturer told me it was balanced. i put it together and it vibrated. it might have been ok if i had ran a 400sbc balancer. but, it wasnt an option due to the serpentine belt. hopefully this isnt your problem. if so, it wont last long without pulling it out and having it balanced.
07-02-2008, 09:00 PM
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i missed that you had a fluid dampener. call the people that you bought the rotating assembly from and ask for a part # for the balancer to make sure its right. BTW, i doubt poly bushings would cause this problem. i ran a solid trans. mount for 2 yrs. and had little vibration.
07-02-2008, 09:14 PM
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Thanks.
My problem is, why does the engine only shake/vibrate a) when it is warm in closed-loop, and b) when the engine is under load? If it was out of balance, would it not shake/vibrate whether it is cold or hot and at that certain RPM regardless of whether it is loaded or not?
My problem is, why does the engine only shake/vibrate a) when it is warm in closed-loop, and b) when the engine is under load? If it was out of balance, would it not shake/vibrate whether it is cold or hot and at that certain RPM regardless of whether it is loaded or not?
Last edited by fa63; 07-02-2008 at 09:21 PM.
