Vibration in a 383 stroker motor?

[Pete104]

Hello. I have an issue with a repower. Started out with a 1989 350 MAG, s/n OC 409667.
Let me say that I have been "certified" w/mercury marine since 1983. Among others. Have been put through plenty of obsticles & other "hoop jumping", even had to stand corrected once or twice! LOL

The original engine had 1900 hours on it. Constantly having to do something. Valve job one year. The following year started getting water in the oil. Cracked head. Owner had enough.

We are repowering w/ the "stroker" version of SB Chevy. The place we bought from, their version of "partial engine", crank & pistons up to heads installed & valves adjusted. Fine, I've done alot of engine replacements to 1 degree or another.

Bottom line is engine has great everything, oil pressure, temp & charges all on known good test equiptment. BUT, it's got a vibration! Drive off, no water going thru it. Just light it up & at 1500- 2000rpm it's pretty significant.

It does have the 8" balancer (external) & original flywheel. All the research I've done leads me no where, ever been there?LOL

Thought maybe some merc techs have experience with this!

Thanks

 

[Bondo]

Re: Vibration in a 383 stroker motor?

It does have the 8" balancer (external) & original flywheel. All the research I've done leads me no where, ever been there?

Ayuh,... If the balancer, 'n flywheel are from the 350Mag,...
I'm guessin' the long block ya got is an externally balanced rotating assembley...
You'll be needin' a 400 SBC balancer, 'n flywheel...
A call to the Builder should clear up the question...

 

[Pete104]

Re: Vibration in a 383 stroker motor?

I've got the balancer for 400 SBC. No body has brought up the flywheel, although I've questioned it. Ran out of time to call on a Saturday.

I'll post again on monday with what they tell me, but I'm thinking your spot on!

Thanks

 

[Pete104]

Re: Vibration in a 383 stroker motor?

I talked to somebody today at "rebuilder", telling him all I've done. He swears up & down, the balancer is all I need. As he suggested, I sent an e-mail to the guy in the warranty dept.

What designates how an engine is balanced? Internal vs External

 

[picklenjim]

Re: Vibration in a 383 stroker motor?

It does require a 400 flywheel or you can get a "balance plate " to use with a 350 flywheel. Check out these links.
http://www.jalopyjournal.com/forum/showthread.php?t=8241

http://www.worthpoint.com/worthopedia/sbc-383-400-chevy-flywheel-balance-53400388

On an internal balance the balancing is all done in the crank and you would use a zero balance flywheel and balancer. External the balancing is done with the flywheel and balancer.


Personaly I would recomend a 400 flywheel over a balance plate.