VegasJen

on a 1st gen SBC what size came factory?
(i think) i know that up to 400ci motors were internally balanced, 400's were externally balanced. is this correct? and what would be the difference in relation to the balancer? if so, why would you not balance a 400 internally?
i'm looking at a streetdampr from fluidampr when i do my rebuild. they list both a 6.25" and an 8" for the SBC. what's the difference? when and why would i want to use a certain one?
your personal experiences, opinions and any links would be appreciated.

Monty

A variety of sizes came stock on from the factory - depending on engine option and SBC or BBC.

Yes, 400's were externally balanced from the factory using dampers and flywheels/flexplates with offset weights to help balance the crank. A 400 can be internally balanced, but mallory (heavy metal) is usually needed. This adds a little to your balancing bill, but neutral dampers and flywheels/flexplates are usually cheaper so some of the expense is offset.

A small damper will reduce rotating weight, so the engine will rev slightly quicker, but the difference is pretty negligible unless you're racing competitively. But I've always used the 6 1/4" or 6 3/8" on my engines. Some people claim that the larger dampers are more effective at dampening torsional forces, but I've never seen any data to validate that claim. Even so, as with the quicker reving benefit of the smaller dampers, the dampening effectiveness advantage of the 8" over the smaller one is probably equally negligible.

Another consideration is space. It's not an issue with the C3's, but some later model Vette's sometimes cannot use the larer dampers because it hits the front crossmember.

My opinion - use the smallest one available for your application.


[Modified by Monty, 1:52 PM 8/10/2002]

Zpeedstr

Is there a 6.25" fluid balancer 6 groove pulley setup that can replace the stock LT4?

SmokedTires

Clutchdust I installed the Fluidampr 6.25" on my 74 SBC with no problems. I too like the idea of less rotating weight :yesnod: .

gkull

Zpeedstr I don't understand what your asking? the pulleys bolt onto the front of the damper. I use a 6 1/4 SFI rated.

Zpeedstr

The LT4 uses a different setup, where the pulley and damper seem to be one unit.
I would like to get some underdrive setup if possible.
The stock LT4 6 groove pulley is about 6.75 " diameter.

r

MoMo

I'm going to go against the flow and vote for the larger damper. I also prefer a Hayes billet steel flywheel instead of aluminum, and a nice heavy Lakewood scatter shield.

The reason for my preference is that although the lighter reciprocating weight will tend to make a faster revving engine, I'd rather have a smoother engine at the high rpm's. At 7000 rpm, I don't want to feel even a throb. Of course, my intended application is for racing, track and road type. For that, endurance and reliability are my top concerns.

I don't know if anything's been proven one way or the other, it probably does just come down to preference and theoretical reasoning. If so, that is mine.

Jvette73

I got the 6.25 fluidampr on mine with no problems so far. my stock damper slipped so I upgraded to the fluidampr. Very happy with it and its fully marked with timing incriments already so no need for timing tape.