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383 which harmonic balancer to use?

broncoman6524

broncoman6524

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It's an internally balanced 383 eagle rotating assembly.

Should I use a 8" or a 6"? Or does it really matter?:confused:

Thanks, chris
 
Since it is internally balanced the larger the dampner the better, go with the 8". All factory 400's used an 8" balancer anyhow.
 
Definitely go with an eight inch.

does it have a 1 piece or 2 piece rear main seal? If it's a 1 piece make sure you have the weight milled off of the flywheel/flexplate
 
I would always put a bigger balancer on if clearance allowed and it wasn't going to be revved into the stratosphere (8500 rpm plus)
 
The cam runs out a 5600, dont think it will ever be there...:haha:

It's a one piece rear. Its a flywheel as well so by weight, do you mean like a balancing weight?
 
You better check, Eagle (Summit) says the components are balanced, but the engine assembly is externally balanced. You'll need the SBC400 flywheel or flexplate, and the SBC400 harmonic balancer.
Personally, if it's within budget, I'd recommend the Streetdamper from Fluidamper. It really does smooth out the engine.
Otherwise, the 8" balancer will add to the perceived low end torque.
 
I did some more research, I have an Internally balanced assy. I have the sheet saying it was bluepirinted and the weight of everything.

I read that if you have an internally balanced 383, you have to have a "Zero Balanced flywheel"

And a 400 style balancer.

That all correct?
 
broncoman6524 said:
I did some more research, I have an Internally balanced assy. I have the sheet saying it was bluepirinted and the weight of everything.

I read that if you have an internally balanced 383, you have to have a "Zero Balanced flywheel"

And a 400 style balancer.

That all correct?
Click to expand...
That's a new one. The traditional 383 stroker kits require the 400 balancer and flywheel or flexplate.
I would recommend talking to Eagle (phone).
 
broncoman6524 said:
I did some more research, I have an Internally balanced assy. I have the sheet saying it was bluepirinted and the weight of everything.

I read that if you have an internally balanced 383, you have to have a "Zero Balanced flywheel"

And a 400 style balancer.

That all correct?
Click to expand...

If the engine is internally balanced you need a "zero balanced" flywheel and harmonic balancer. Keep in mind that since you have a 1 piece rear mian engine that the older 2 piece main flywheel WILL NOT work since the bolt circle change from 3.58" to 3"
 
ALL of the 1 piece rear main flywheels come with a small counter weight cast in. So they technicly are not internally balanced.

I would highly recommend you take the whole mess to a reputable machine shop including whatever flywheel and balancer you're going to use and have it balanced. It will cost you around 300 dollars to have it done but you know it'll be right when it's done.
It's possible to have an internally balanced 383 but I sure wouldn't trust pulling one out of a box and putting it together without knowing for sure.
 
and these 2 wouldn't ever be used together would they?

"Zero Balanced flywheel"---internal balance

And a 400 style balancer. -----external balance

that combo wouldn't ever be used together would they?
 
No, from what I've read they can't...well they can but shouldn't.:wink1:

I was told to use a zero balance flywheel and balancer.
 
Glad your checking on this.

I had a guy swear up and down at me over several phone calls that my 383 was fully internally balanced and insisted that I buy a 350 flywheel and balancer.

Needless to say, it shook and ran like crap.

I called back and insisted I talk to one of the guys who build the engine.
First thing he told me: You need a 400 flywheel and balancer!!!!

I had to take the whole freaking Blazer back apart (slight exaggeration) to get it changed over to 400 parts.

Best part, The wouldn't even consider helping me pay for the extra parts. Thank god I did it myself and didn't have to pay anyone to do the work.

Now I've got a stinking 350 flywheel and balancer sitting in the garage that I have no idea if I'll ever use.

Good luck man!

-Ben
 
Unless Eagle specifically says it's "internally balanced", and guarantees that in writing, I wouldn't bet on it.
I don't think it can be done without adding heavy metal to some crank throws.
Once you have it built (with the 400 balancer & flexplate or flywheel), have the reciprocating parts "spin/balanced" by a shop that builds dragster engines. :wink1:
 
Is it really that big of a deal that it's perfectly balanced?

Now, I'm confused as to why they even offer a blueprinted/internally balanced kit.:confused:

The cam runs out at 5600, so the rev limiter will be set at 5300. Don't plan on spinning it that hard for very long, or very often.
 
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