vibration in new engine
 

:( my new 306 has a very odd vibration 2800 and above and gets worse the higher the rpm upto 4500 (that is the highest Ive let the rpms go) it does it free rev or driving, I have also swaped in a c-4 with the 50 oz flexplate the crank # shows to be out of an 87 truck, any pointers please, would anything ignition wise or fuel systeme cause this.... looking for somthing simple preferably.....I can wish right.

Re: vibration in new engine
 

Was the rotating assembly balanced at assembly, including with the balancer and flexplate? Was your converter balanced? Has the balancer slipped? Just a few things to check, but it definitely sounds like a balancing issue. '87 truck...might this have been a 28 in-oz crank?

Re: vibration in new engine
 

I thought all post 87 cranks were 50 oz balanced. The rotating assembly was not balanced together. I bought the short block from a builder in Indy, then finished it off with my parts. The only thing I did not take into consideration was the converter. It came with the trany. Is it possible to have the converter balanced seperately, I know this probably would not be ideal for your application but for just a hobby car for shows and occasional strip time would this be sufficient

Re: vibration in new engine
 

Check your PM. Since its an Indy Performance shortblock, I'd bet the problem is in the rotating assembly itself.

Re: vibration in new engine
 

FWIW, 87 trucks did have the 50 oz setup.

Re: vibration in new engine
 

I was having the same issue. I am not completely sure it is fixed ( 2 feet of snow will do that) but I put new Romac balancer on mine and I can tell a big difference right away. Plus, my old one was really fucked up. I would check into this route. The Romac can be had for $200 on ebay. That is where I got mine.