Correct me if I'm wrong please. 400 cranks, whether used in a 400 block or 350 block or even a 305 block?are externally balanced correct? Which I think would make them unique when compared to other small block cranks in that, unless otherwise balanced internally with mallory, would require a harmonic balancer and possibly flexplate with weights on them. My questions are as follows: Does anyone have or have seen a 383 350 block -400 crank combo that they used a 350 damper or an aftermarket damper that was not for an externally balanced crank? Do harmonic balancers make a difference when it comes to strokers versus non-strokers? :confused:

 

I have a eagle 3.75 stroke 350 main crank with 5.7 rods to make a 406. It's all internally balanced. I use a fluiddamper.. actually I should say I will be using a fluiddamper. However I was shocked that the machinest when balancing my crank said he didn't need the balancer since it was a fluiddamper.. I thought they needed the weight on both ends anyways.. I don't know.

 

Quote:

"My questions are as follows: Does anyone have or have seen a 383 350 block -400 crank combo that they used a 350 damper or an aftermarket damper that was not for an externally balanced crank?"

I think Scat has a crank that will internal balance but must use a 6 in connecting rod if memory serves correct .

I'm not sure what your wanting but if it is a 6 inch external dampner BHJ has one . That is what is on my mouse motor :steering: with a balance plate on the rear and a 350 flywheel .

 

I'm aware that internally balanced cranks, especially aftermarket cranks, use neutral balanced dampers as they call them. But my question is: If you use a externally balanced crank,to my knowlegde, you must use a damper that has weights or some type of weight adjustment therefore making the damper an important part of the assembly not allowing you to just bolt on a internally or neutral balanced damper on an externally balanced set-up? correct? I would think a fluid damper is consistant in it's weight whether internally balanced or externally balanced therefore not required when balancing your set-up. Also it's possible that somehow? The fluid inside makes it damp any harmonic vibrations versus weight? My question rises because another forum member asked the question on how can he determine if an engine (SBC) is a 350 or 383? To make it short, I told him although not 100% he can check the harmonic balancers say 8" 400 balancer versus 8" 350 or smaller balancer to help him determine from the outside. Another forum member said that "harmonic balancers have nothing to do with it?" I believe they are not interchangeable and harmonic balancers do play an important part. Eventually we all agreed that the best way to check displacement was to use a volume meter. But I want to make it clear that balancers do have something to do with it. Can anyone correct me if I'm wrong. :confused:

 

I believe it is normal for a fluidamper balancer to be left off for crank balancing and to use a different balancer if external as the fluidamper does not get activated without the cylinder pulses. I could have it a little wrong but i don't think the machine shop was off.
bob

 

The situation, in a nut shell: An unbalanced 400 crank, which is the stock, 400 balance, requires stock unbalanced damper and flywheel/flexplate. By stock, I mean the "stock unbalance", not necessarily, factory parts. This is regardless of whether it has the stock 400 main bearing size for a 400 block or the mains have been turned down to the 350 main size to fit a 350 block to make a 383. Standard 350 parts are required on a crank that has been manufactured or modified for "internal balance". Regardless of which combination is utilized, a custom balance job should be performed on any assemblage of non factory parts. I hope this helps make things more clear. Good luck, and...

RACE ON!!!

 

Short answer is YOU ARE CORRECT

 

Thank you Black Bart! I talked to my machinist and he says anyone who thinks harmonic balancers don't have anyhting to do with it should find a different hobby. Not a big deal! I just thought it needed clearing up, also don't believe anything you hear or read and only believe half of what you see. Thanks :thumbs: