Vibrations on a new rebuilt engine
Thread Starter
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Joined: Nov 2005
Posts: 50
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Vibrations on a new rebuilt engine
Dear ladies and gentlemen!
Please can you help me for this big problem.
With the help of an engine builder (tuning company) i rebuilt my engine for a supercharger corvette C4 LT1.
Now it happens when the engine run (and also when we dont´t drive) at 1200 rpm the sterring whell begins to shake. And At 4000rpm and more the engine and the complete car will vibrate (to judder).
Is there a mistake at the fine balancing of the crankshaft?
I read that the eagle crank has an internal balance and the ATI damper is to zero balanced.
I think my stock crank and pulley have an external balance. And the engine builder makes the mistake, to do also an external balance for the eagle crank and didn´t see that the ATI pulley needs a internal balanced crank.
Could this be the reason for the vibrations?
Best regards,
Juergen Schimak
We used this new components:
> ATI Super damper 6+8 RIB crankshaft balancer/pulley for 1992-1996 LT1/LT4 Corvette
> Eagle 3.480" 350 (internal balance) 1875 bobweight, 4340 forged steal Part. No. 4353348057LA
> Eagle ESP H-beam connections rods 6.000" ligthweigt, 545g, Part. No. CRS60000BLW
> JE Pistions Extreme Duty 23° Inv. Dome, 355 Cubic Inches, 4.030 Bore sizes, 3.500 stroke. 6.000 rod lengh ,1.250 compression distance, Part. No. 218591
Please can you help me for this big problem.
With the help of an engine builder (tuning company) i rebuilt my engine for a supercharger corvette C4 LT1.
Now it happens when the engine run (and also when we dont´t drive) at 1200 rpm the sterring whell begins to shake. And At 4000rpm and more the engine and the complete car will vibrate (to judder).
Is there a mistake at the fine balancing of the crankshaft?
I read that the eagle crank has an internal balance and the ATI damper is to zero balanced.
I think my stock crank and pulley have an external balance. And the engine builder makes the mistake, to do also an external balance for the eagle crank and didn´t see that the ATI pulley needs a internal balanced crank.
Could this be the reason for the vibrations?
Best regards,
Juergen Schimak
We used this new components:
> ATI Super damper 6+8 RIB crankshaft balancer/pulley for 1992-1996 LT1/LT4 Corvette
> Eagle 3.480" 350 (internal balance) 1875 bobweight, 4340 forged steal Part. No. 4353348057LA
> Eagle ESP H-beam connections rods 6.000" ligthweigt, 545g, Part. No. CRS60000BLW
> JE Pistions Extreme Duty 23° Inv. Dome, 355 Cubic Inches, 4.030 Bore sizes, 3.500 stroke. 6.000 rod lengh ,1.250 compression distance, Part. No. 218591
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
Juergen,
If yours is a second gen (one piece rear main seal) and they internally balanced the whole thing, you might be in for a hassle.
It seems that GM saw fit to internal balance the front half of the crank and external balance the rear half. It's mostly due to the lack of counterweight room inside the case. The single piece rear main required the rear to be ground to a standard Dia, removing the small but significant rear flange weight.
You can try pulling the extra counterweight off the flywheel, If they balanced the crank neutral without it that will solve your issues.
As a rule of thumb I give them the flywheel,clutch whatever Im going to be running on the assembly (with the special exception of brand new uncentered ATI dampers) to be balanced.
If yours is a second gen (one piece rear main seal) and they internally balanced the whole thing, you might be in for a hassle.
It seems that GM saw fit to internal balance the front half of the crank and external balance the rear half. It's mostly due to the lack of counterweight room inside the case. The single piece rear main required the rear to be ground to a standard Dia, removing the small but significant rear flange weight.
You can try pulling the extra counterweight off the flywheel, If they balanced the crank neutral without it that will solve your issues.
As a rule of thumb I give them the flywheel,clutch whatever Im going to be running on the assembly (with the special exception of brand new uncentered ATI dampers) to be balanced.
Pro
Joined: Dec 2002
Posts: 704
Likes: 16
From: Dallas Texas
I take my entire rotating assembly to have it balanced (i.e., clutch, flywheel, crank, bearings, rods, pistons, rings, crank hub, and crank pulley). Who did your balancing work and did they have the entire rotating assembly?
Melting Slicks
Joined: Mar 1999
Posts: 2,535
Likes: 2
From: Rochester NY
This is exactly what happened to me my 383LT1 with internal rotating assembly balanced yrs ago. It would shake whole car at 4000rpm, it is undriveable. To solve this vibration problem. You need to remove the inspection cover and crank the motor a few times until you see the counter weight on the flywheel. Remove the counter weight, 2 bolts. Your should be good to go. It really easy to do. Good luck man.
Bruce
Bruce
Thread Starter
Advanced
Joined: Nov 2005
Posts: 50
Likes: 0
I gave all the engine parts to my engine builder. I´ve buyed the eagle crank in his office. Than he takes my stock GM flywheel and the ATI balancer to do the balancing on the crank. He never takes the stock GM balancer to the balancing. (But i showed him the stock one).
I´ve seen at the installing of the engine, that there is a bigger weight on the (automatic trans) flywheel as before. But at this time i didn´t have experinece (notion) for balancing a crank and so i don´t think this is wrong. Now i know that this is an external balancing, but this is not my job to know this, because i´ve payed an engine builder to do this job correct. I think such a mistake should not pass an "expert"!
But i think it´s not the best way to remove only the weights of the flywheel, beause i don´t know what really happens with the crank at the balancing. So i think it´s the best way to do a internal balance again. Can i use my stock flywheel, if i remove the weights?
Best regards,
Juergen
I´ve seen at the installing of the engine, that there is a bigger weight on the (automatic trans) flywheel as before. But at this time i didn´t have experinece (notion) for balancing a crank and so i don´t think this is wrong. Now i know that this is an external balancing, but this is not my job to know this, because i´ve payed an engine builder to do this job correct. I think such a mistake should not pass an "expert"!
But i think it´s not the best way to remove only the weights of the flywheel, beause i don´t know what really happens with the crank at the balancing. So i think it´s the best way to do a internal balance again. Can i use my stock flywheel, if i remove the weights?
Best regards,
Juergen
Drifting
Joined: Nov 2003
Posts: 1,637
Likes: 2
From: Honeoye Ny
If your going to have it rebalanced, then you can reuse the flexplate as it sits.
But...It might not be your only cause.
Heck, just last month my dad got a bum torque converter for his tow rig. It shook the entire vehicle at varying itensities at all RPMs.
If the converter is new(since the last time you had the car together) it's possible that it's causing your troubles.
But...It might not be your only cause.
Heck, just last month my dad got a bum torque converter for his tow rig. It shook the entire vehicle at varying itensities at all RPMs.
If the converter is new(since the last time you had the car together) it's possible that it's causing your troubles.
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