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Vibration at 2100 RPM
All aluminum FE 452 stroker with I believe Eagle rotating assy, Fidanza aluminum flywheel, Mcleod clutch. Motor has been balanced and dynoed by the builder and has 450 miles on it now.
The problem is a vibration that seems worse with higher RPM. It is really noticeable at 2100 RPM on the way up the rev range in any gear. It is downright awful at 2100 on the way down through the rev range where it really shakes the car and rattles the drivers side pipe. It is the same in all 4gears. It seems to be getting worse or at least more audible. Has anyone run into this problem or do you have any suggestions on what I should be checking. Thanks FE gurus. |
Check to see that the damper ring has not slipped.
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Was the damper and flywheel that is on the engine now the same ones used when it was balanced? I think I would talk with the person who balanced it first.
I suppose a clutch or pressure plate could cause problems if it wasn't zero balanced. If memory serves me, the 428 FE was the only FE to be externally balanced from the factory. |
A bad balancer is the only "easy" fix I can think of -- two seconds with the timing gun will tell you if it has slipped. I take it the engine seems to run right other than the really bad vibration? Was it dyno'ed? If it didn't vibrate on the dyno then that's a tip right there.
EDIT -- OK, I see it was dyno'ed. If it didn't vibrate on the dyno (and I can't imagine he'd let it go if it did) and it vibrates really bad just revving it at a stand-still, then you could take the tunnel out and disconnect the transmission, pull the clutch, and run it again with all that off and if it still vibrates you're going to have to pull the engine. That might at least let you spot some loose pressure plate/flywheel issues without having to pull the entire engine first. |
Bad u-joint or driveshaft out of balance...
Check to make sure motor and trans mounts are tight. |
mm -- does it not vibrate when you rev it at a stand-still?
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He kept saying, any gear, all 4 gears, etc, etc. I took it to mean that it only happened as the car was rolling down the road.
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You don't understand how joyful I am to know that you agree with me Patrick. ;)
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However after re-reading, the fact that it is worse when slowing down than when accellerating is most puzzling. I would say the input shaft in the tranny is also turning at engine speed. Bad bearing in tranny on input shaft??? Rev engine to 2100 rpm with transmission in nutral with clutch out, car parked. Also rev it with transmission in gear, clutch in, and car parked. |
If you rev it standing still it is barely noticeable. It's almost the same as going up through the revs where you just feel it. If I stomp the clutch as it's going down and thru the 2100 shake it stops immediately but it also is out of the rev range immediately. The driveshaft was so close on balance (partly cos they're so short) he ground balanced it rather than add weight. The motor has not been touched since dyno other than putting carb and TP on and adding the log and retorquing the two manifold bolts. It does it in every gear so it's not driveline I'm thinkin. It does feel like the flywheel area and shakes back from there. The engine builder and the flywheel/clutch supplier all agreed it was zero balance on both their assemblies and they didn't need to be balanced assembled. I just checked the timing it's at 16 deg at idle. Balancer nut is tight. They are good suggestions thanks. If this thread gets hijacked I'm unsubscribing to my own thread.
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Another good check thanks. It is barely noticeable on the way down sitting still and revving the engine. I'll try clutch in and out in the a.m. I would guess the same from trans forward due to the every gear no road speed effect.
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Unless you bolted on the weights that came with the Fidanza flywheel, then it is indeed 0 balance. Pressure plates are always 0 balanced as well.
Has the problem existed from the first startup, or did it just appear? |
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Barely noticeable on the way up moving, barely noticeable on the way down sitting still. Weights are in the box they came in. I don't know if my awareness or neurosis has increased but it almost seems worse as you drive it. I didn't notice it on first drives.
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You may have to drop the trans real quick just to check things out....make sure the flywheel bolts are still tight, pilot bushing looks good, etc. I'd take a look at the input shaft on the trans as well....make sure the bearing doesn't have any slop in it.
If it does it with the clutch out in neutral, then it has to be between the flywheel and the transmission. |
It is seeming to me that it is a shaft that is not necessarily out of balance, rather not being held centered and allowing it to wobble off center of its axis of rotation. Like a bad bearing, worn shaft. Even a pilot bearing that the input shaft is loose or too short to reach it.
I had an industrial blower with a loose bearing on the shaft that the vibration was worse when slowing down than it was when speeding up. Any way if the car is in gear and stopped with the clutch in, the input shaft and clutch will not rotate. However in nutral clutch out the shaft, and clutch will rotate. Try to simulate the rpm coming down as if driving. On the pilot bearing, if it were loose, every time you push the clutch in and let it back out, the alignment could change. Does the vibration seem to randomly get better and worse as you shift? |
We balance the flywheel on the engine after it is balanxced to make sure that it is zero we then install the pressure plate and chack it. They are almost always out some. We will move the pressure plate to all three locations that it will bolt up at and see which one is the closest. We will then balance it and stamp where it is bolted so that it gets bolted up there again.
Thanks, Keith |
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