Hey guys, I used one of those bars you insert through the transom to center the motor before puttin the outdrive back in. I thought it seemed real smooth, but if the motor is off even a little will I be getting a vibration at idle, NOT in gear? I got a nasty vibration throughout the rpm range and trying to cancel all possibilities before I yank the motor again.

I would be surprised if that would cause your problem. My experience if they are off any it is very hard to install the outdrive. Specially an Alpha.
Did you have the flywheel off when you had the engine out? Did you get it back on correctly. I have seen BBC when the dowl is missing the flywheel will still bolt up and you will have a bad vibration
Take the outdrive off, put a garden hose in the input hose and run the engine without the outdrive. Or just start it without water and see if you have the vibration. Assuming you do not have a seawater pump.

That in most cases won't cause a vibration like your speaking of, check to see if your Harmonic Balancer has spun. I have seen this happen a few times and that will create a nasty vibration throughout the rpm's.

Need LOTS more info. here. But if you used the alignment tool and you could slide it in/out by hand it is NOT an alignment problem. You running this on hose trimmed way up or cranked hard to one side? Gimble brg. and U-joints real good? Rebuilt engine that requires external or internal balance and not properly accounted for? Check it out - Let us know - Can probably help. --- Jer

ya it was a shortblock 355 inch reman, edelbrock headed, hyd cammed, performer intake. No big deal motor. Shortblock is supposed to be of 80-83 vintage. Has 2 piece rear main. Used a brand new flywheel and bran new balancer. If I remember I bought flywheel and balancer that was for an internal balance engine, arent all the 350's internal? The balancer is an 8inch. The outdrive whent right in, so I kinda figured thats not my vibration.

The vibration is typical of a bad balancer, but with everything being new Im just trying to rule everything out. Outdrive is straight, trimmed down on a hose with ears. Was beginning to break in the cam and thats a no go with the vibration.

Its an external balanced engine. I bet you have the flywheel on wrong or the wrong one.

I thought the only externals were the 400? Im no chevy guy by any means mind you. Flywheel is on correct for sure, may have the wrong one

u joints

it was fine with the old 305 in it last year at the last outing, if it was the ujoints that would be great. I was gonna pull the drive tommorrow and just fire it up for 5 seconds and I would know right away if the vibration was still there

350 cid are internally balanced, 400 small blocks are externally balanced. That still doesn't mean that you don't have the wrong or bad balancer/flywheel even though new???