Thread: 6" vs 8" balancer SBC

Tweet

Is one better than the other? My 76 SBC came with the 8, but I'd like to run the 6" just to clean things up.

Thanks for you oppinions!!!

I wondered about the same thing. My 350 came with an 8 inch, and when I ordered a new one from Summit I asked the tech there if I could go to a 6, and he suggested not changing it as it might cause some problems. But that was just one mans opinion, so it will be interesting to see what some of the guys on here who know say about this.

Don

You can do either one,but the 8 inch produces more spooled up engery off the line for racing.The smaller one will help the engine rev faster due to the reduced mass.It must be correct for the balance of the engine also.
It all comes down to application and personal preference,will it hurt the motor no,will it be the best one for your application ,only you know that.I also remember reading that small one and light weight ones do not do as good of job dampning the harmonics as a heavy one.Were talking minimal amounts but enuff to be noticed in crank bearing wear .Those are the basic differences that I personaly know about ,there may be more ?

O.K., here's my take on it. Nobody has ever told me the reason there are so many different dampers for a small block Chevy, but I'm thinkin' the factory engineers know more than I do. I do know the reason for a damper and it makes sense to me that because there are different strokes and weights of reciprocating assemblies, it takes different dampers to dampen the harmonic oscillations created in the crank every time a cylinder fires. If it didn't matter, the Chevy engineers would only have made one application for all small block Chevies. Take a look at a damper used on a 3" stroke crank and then look at the damper fitted to a 3.750" stroke crank. Lots of difference. The longer stroke crank has a longer "arm" and I reckon it takes more damper to dampen the oscillations because the arm deflects from center farther and springs back farther. Like I said, this is just my own figurin', nobody has ever explained it to me. And by the way, the piece is a damper, not a balancer. It doesn't balance anything.

For you who don't know what happens, every time a cylinder fires, there is pressure placed on the rod journal. That pressure bends the material from the journal to the center of the crank. It will only bend so far, then it stops and begins springing back the other way. It springs back past center until it can't go any farther, then it springs back the other way, etc., etc. etc. These oscillations are called harmonics. It is the job of the harmonic damper to dampen these vibrations so as not to destroy the crank.

I can't remember if it was on this forum or another one that I was reading recently. This fellow was trying to find a good crank that wasn't cracked for his DeSoto hemi I think. He had found a number of them that were no good because they didn't use a damper at the factory and harmonics had cracked every one he found. He finally found a good crank and was asking about fitting a late model Dodge 340 damper to it.

If it were my crank, I'd research what the factory fitted it with and use that particular damper, pretty or not.

Look at this list of dampers from Damper Doctor for small block Chevies.....
http://www.damperdoctor.com/Merchant...egory_Code=CHE

Richard's logic was pretty much what the Summit Tech said..........it came on there as an 8 inch for a reason, so don't change it. Made sense to me, so I didn't go smaller.

Don

HD or truck could see a hi load on the crank at low rpms the damper would be bigger to help this but if you are not run it in a truck them you could swap them out but most think the big damper mean HP engine gm used big dampers on all HP stuff in the 60/70 small and big blocks but the 454 had a big damper to help with the external balance of the crank it let them put the weight in the hub of the damper and the 400sbc to. to get the mass down a lot of guys run a small dammper to spin up faster i have all ways lean to the side of caution on hot engine or all out races engine not really not knowing where in time or how much harmonic there will be and if the smaller one could help dammpen some of it when it comes. from what i know it can happen at any rpm more or less so a big dammper has more surface to help controll it the oem ring type but still if you want to a small one that they say can do a much better job at it like a TCI rattler or ati then you could run a small one

Hmmmm... What about using a 305 damper on a 350 (or vice-versa). They both have 3.48 stroke, but the dampers look different.

Ya know, Midgets & Sprint cars don't run balancers and do not experiance problems "or none I've ever seen or heard about"... I just finished building a limited 305 chevy for the kids sprint car and because we are running the standard water pump I put a new 6 inch lightweight balancer on it. Guess we'll see if that cast crank holds up..... I would never run anything except an 8 inch balancer on any of my street vehicles as I would rather be safe than sorry,only reason for the small one on the 305 sprint motor is I'm lookin for every thing I can get within the rules........