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Discussion Starter #1
After the Sprint sat for more than six months due to an engine rebuild, it now has a vibration that I can't figure out. When in park (TH400) and I pick the rpm's up to 2200 and above it vibrates the entire car. At around 2500, which is the stall speed the whole car jumps like it is going to take off.When in neutral I don't have this and little to no vibration is present. When driving, again, anytime the rpm's hit 2200 and up it vibrates. I changed the harmonic balancer initially thinking the previously one had gone bad but little to no change.
I'm leaning toward a TQ issue but really have no idea. The trans/bell housing are bolted up tight. The weight is on the flex plate and all the bolts are present. I don't know where to go from here!
Any advice would be appreciated!
Thanks.
 

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What engine does it have? If you replaced harmonic balancer and/or flex plate you may have used the or been supplied incorrect parts. 350 and 400 CI engines are balanced differently. 350 is internal and 400 is external.
 

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Discussion Starter #3
I guess that would be important wouldn't it! It's a MK IV 454. On the original build it was balanced and blueprinted. This build was just honing, rings, bearings, gaskets and such. Nothing that would have affected the balance.
 

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Discussion Starter #5
Yes, it is the same TC and flywheel as before. I'm not familiar with any crank dowel hole alignment. Please educate me. As for clocking it, all of the bolt holes lined up with the crank. If there is a specific way they should go other than that than I'm ignorant of it. The flywheel will only go on one direction without hitting the block. And yes, the TC is all the way back.
 

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its a line-up hole for the dowel pin in the crank [ that's usually never there ]
you just line up the holes.. it only matters on external balance motors
like the newer 1pc seal 350's, 400 sbc, 454 bb..
fw 454 FW WEIGHT.jpg fw Brokeflywheel dowl.jpg
1st pic is the weight on a 454, if your running a zero balance flywheel..
 

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Discussion Starter #7
Well, I just learned something. I'll have to check it out. (Not looking forward to it but...) I must have gotten lucky before i guess.
 

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Discussion Starter #9
Well JJLT1, That was the issue. My Flex plate was 180 out so my son in law and I spent several hours under the car yesterday rectifying the situation. When it was all said and done there was no trace of vibration. I took it for a spin today and it was nice and smooth, well as smooth as a built 454 can be anyway. Thanks so much for sharing your knowledge.
 

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Discussion Starter #11
Someone can correct me if I'm wrong but as far as I know dieselhead all of the Mark IV big blocks are externally balanced engines.I think it was after 1989(?) that they went to internal balancing. These big block also use a two piece rear main seal.
 

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wtg Rowdy glad it helped..

yea the 86 and up 1piece seal sbc350 is only Ext Weighted on the flywheel end..
sbc 400 was Ext Bal on both ends..

not all BBC were Ext Balanced,, the 2piece seal 454 are Ext Bal.. both ends..

I believe the 396 and 427 were Internal.. IIRC [CRS]
not sure on the 366 truck motor..

I have no idea on the late model stuff..
 
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