I am purchacing an 383 rotating assembly kit from eagle and am not sure whether i want it internally or externally balanced. I know i eventually want the assembly internally balanced, but i also know factory balances aren't the best. Should i just buy an internally balanced kit and have it rebalanced or will the kit be balanced well enough to start with? And if i do buy the kit internally balanced, what else to i need to buy? i know flexplate, harmonic balancer, and dampener are names that have come up in my research that i need to buy. If so, what types of the above do i need (number of teeth, degree range, ect.)?

 

Just get yourself the internally balanced kit and you're good to go. You won't have to do anything later that way. And yes you will need a harmonic balancer and a flexplate or flywheel if you have manual tranny

 

That depends on whether or not the kit comes balanced or not.

 

Now ive seen all of the parts ranging from $60 to $300. I think the harmonic balancer was either iron or steel. How do I choose? Also what parts do i need exactly if i have a manual shift? I know you said balancer and flywheel, but do i need a dampener?

 

A dampener is the same as a harmonic balancer. You will need the flywheel clutch disc and pressure plate throw out bearing and pilot bearing all of which can be bought as a kit minus the flywheel of course. If you're putting together a 383 be sure you get a good balancer for it. As far as choosing parts for your engine ask questions. Ask the people at Summit or wherever you are buying you crank kit. Ask a lot of questions, if they don't have answers stay away from that vendor.

 

Except "balancer" is the wrong description. The correct description is "harmonic damper". It'll probably take a little longer than forever to purge "harmonic balancer" from the vocabulary, but I'm trying.

 

Its especially difficult when harmonic damper manufacturers refer to their product as "balancers".

 

......and the other thing that rubs me wrong when this damper thing is discussed: calling it a "dampener"! To dampen is to "make wet" ; to damp is to quell vibration. D)

 

"Dampen" is also to "dull, deaden or depress", so "dampener" is also correct.

 

I KNOW It's a shame when even the authors of the dictionaries cave in to the illiterates, just like putting "ain't" in there. It used to be that Eastern Kentucky had no influence over the English language

 

Yeah, what were they thinking in the 1600s when that usage originated? I bet they had no idea the irritation it would cause.

 

When you have a spring/mas system, you say, "What is the dampening ratio?" Not, "What is the damperer ratio?" Dampener is the correct term.

 

Hah! You can't even spell, and we should believe you?
You say: "What is the damping ratio."

 

I disagree:

---Main Entry:
damp·er
Pronunciation:
\ˈdam-pər\
Function:
noun
Date:
1707

2: a device that damps: as b: a small felted block to stop the vibration of a piano string ----

Seeing as how a damper is a device that stops the harmonic vibrations of a crankshaft, it is the correct term.

 

COUGH... go back to the library.

Personally, I don't think what kind of dampener you get matters as long as everything is correctly balanced. I suppose it might make a difference if you are going to be doing some higher RPMs, but for anything that would be mostly street driven I don't see how it could be a big issue.

The flywheel will make a difference as far as internal or external balanced. There will be a weight added to the flywheel for external balanced and no weight on an internally balanced. Other than that I think you will want to go with a 153 tooth, with a 12.78" diameter I believe. If you go with the 168 your diameter will jump up to 14.xx and you will need to get the accompanying starter for the larger flywheel. If you are using a starter after 1986 you will want the 153 tooth. Pre 86 and you can go with the 168.
From what I can tell 1 piece rear main seals are usually externally balanced unless it's a 2 piece that has been converted over. So you can look at it as an aspect of deciding based on your block I suppose. If it's a 2 piece main block, you can go with the internally balanced crank and not have to buy the extra conversion parts.

Someone correct me if I'm wrong on all that, otherwise that's the way I'm going to remember it.

 

Yes, it does make a difference which one you use. The factory 400, 3.75" stroke crank, used a weighted damper and flexplate/flywheel, aka "external" balancing. The aftermarket came up with internal 3.75" stroke crankshafts, and if you get one of those cranks, you do not want to used a weighted damper.

The one-piece rear main seal cranks (here we go, explaining this again) needed a weight on the flexplate/flywheel to replace a counterweight that was cast into the 2-piece rear main seal cranks external to the rear main seal. That is not the same as the 3.75" stroke crank "external balance" weight on the flexplate/flywheel (the "externally" balanced SBC 400's had that counterweight cast into the crank as well). They are different things, so whether you get a one- or two-piece rear main seal stroker crank, you need to know whether it was made to be internally or externally balanced, and use the right harmonic damper and flexplate/flywheel.

Personally, to answer the originator's original question, I would get an internally balanced kit that was balanced.

 

So if i have a one piece rear main block, am buying and internally balanced rotating assembly, and having a machine shop custom grind a camshaft, all i should buy is a nuetral balanced harmonic dampener and a 153 tooth flywheel? Did i understand this correctly? and thank you again for your time and patience. Just know you are helping a new car enthusiast become a bit more educated.

 

You'd need a neutral balanced dampener like the one used on any stock SBC except the 400, and a stock-balanced flywheel like the one used stock on any 1-pc RMS SBC.

 

Do you know if the flywheel has 153 or 168 teeth?

 

A T5 needs a 153 tooth flywheel.

 

Glad to help. Warding off misinformation is a full-time job, though. . .

(All 3rd gen V8 flexplates & flywheels were 153-tooth.)

 

When i purchased my eagle internally balanced 1pc rms rotating assembly they told me i could use the factory 305/350 dampener but i would need to purchase a neutral balanced flex plate/flyeheel.But it sounds like you guys are saying that you can use the factory 1 pc rms flex plate????

 

The suppliers are correct.
Internal balance is just that ,internally balanced so anything bolted on the outside is neutral.You would need a neutral balance (2 pce sealstyle ) flywheel.

1 pce seal engines are neutral balance at front , same as all SBC except 400 BUT external balance at rear.That is why the 1 pce seal flywheel/flexplates have a weight on them.

Problem is the two cranks have different bolt patterns for the flywheel so you would need a 1pc rms flywheel neutral balanced .

 

See, here we go again. The 1-piece rear main seal cranks are no more "externally balanced" at the rear than the 2-piece rear main seal cranks are. After all, the weight on the 2-piece rear main seal cranks is external to the crankcase.

Don't call 1-piece rear main seal cranks "external balance at the rear", because that just confuses the issue.

I wouldn't call that a problem. It's a good thing the two different types of cranks have different flexplate/flywheel bolt patterns, because that way you can't put the wrong one on.

And, a "neutral balanced" 1-piece rear main seal flexplate will have a weight on it.

 

Well you are on your own there.
You may be correct from an engineering perpective but the automotive industry considers the crank as part of the internal structure regardless of whether it is actually internal to the block..

GM as well as all the flywheel / flexplate makers refer to 1pce RMS engines as EXTERNAL balance
and the 2 pce RMS as INTERNAL .
The crank is considered internal and anything that bolts to it external.

From GM Parts catalog

Small Block Chevy Flywheel Part Numbers

Part # DIA. Teeth Comments
3991469 14" 168 two-piece seal, internal balanced
10105832 14" 168 86up, 1pce rear seal, ext. balance
14085720 12.75" 153 Lightweight nodular iron, two-piece seal, int balance
14088646 12.75" 153 86-up, Lightweight nodular iron, 1pce rear seal, ext balance
14088648 14" 168 86-up, 1pce rear seal, ext. balance
14088650 12.75" 153 86-up, 1pce rear seal, ext balance

Small Block Chevy Flexplate Part Numbers

Part # DIA. Teeth Comments
471529 12.75" 153 Two-piece seal blocks, int balance
471598 14" 168 Two-piece seal blocks, internal balance
10128412 12.75" 153 86-up, one-piece rear seal ext. balance
10128413 14" 168 86-up, one-piece seal, HD, ext bal
10128414 14" 168 86-96, one-piece rear seal, ext. balance
14088761 14" 168 89-up 350 HO, one-piece rear seal, ext. bal.
14088765 12.75" 153 86-up, one-piece rear seal, ext. bal.
14088767 14" 168 89-up 350 HO, one-piece rear seal, HD, ext. bal

.[/QUOTE]And, a "neutral balanced" 1-piece rear main seal flexplate will have a weight on it.[/QUOTE]

A flywheel that is " neutral " balanced will sit at any position when mounted on a spindle whereas a one with a weight will rotate the weight to the bottom. The weighted flywheel only becomes “ neutral “ when bolted to the rotating assembly

 

Count on the factory to keep it confusing.

 

Yup... suppose you were to build an externally balanced 383 in a 1 piece RMS block. Then you'd have to choose between an "externally balanced" flywheel, and an "externally balanced" flywheel.

I'm convinced GM must have hired Ford engineers.

 

So does that mean i cant build an internally balanced 1 piece RMS 383?

 

Depends what you mean by "internally balance". You can balance the whole rotating assembly any way you want, if you've got the right parts and/or you want to spend the money.