In a few months I will be ordering this short block to build

http://www.summitracing.com/parts/hpe-sp04

and in the ad it says the balance is internal/external. Well whenever I go on summit it only shows harmonic balancers that are for sbc for internally balanced motors. So what harmonic balancer and flexplate would you guys recommend? I don't have the money for a super damper and this motor is going to be a street motor with a visit to the strip like 1-2 times a year. Will never go higher than 6000-6500 RPM

 

The operative word is STOCK. Try not to get all hung up over "internal" and "external". Those words only confuse the issue with otherwise STOCK 1-pc rear-main-seal motors.

STOCK.

Don't outsmart yourself. It takes your STOCK damper and flex plate. New, good-quality replacement, is a great idea, particularly f you intend to stress it out a little bit; but STOCK balance is the key here. Nothing in the bottom end of that motor is ANYTHING BUT stock.

Given that, I'd suggest strongly resisting the impulse to do very much of

Remember, all it is, is a STOCK bottom end.

 

Thanks, this helped a lot but when I'm on summit they are still wanting to know if the engine is internally or externally balanced when choosing a flex plate for a sbc 1 piece and even though this harmonic balancer

http://www.summitracing.com/parts/su...make/chevrolet

is for an "internally balanced sbc" I'm assuming it will still work since it's titled OEM? Thanks for the reply

 

All SBCs are internally balanced, except for the 400.

86-up 305s and 350s have the rearmost bit of internal balance weight located on the flywheel or flex plate, instead of being part of the crank. This gives rise to endless confusion but doesn't change the basic fact that the engine is internally balanced. "Internal" and "external" DO NOT refer to side of the bolt split that the weight is on, even though some of the aftermarket crank mfrs and such, have thrown in the towel and mangle the terms as badly as typical street strokes do.

All dampers for 262.5, 265, 267, 283, 302, 305, 327, and 350, are for internal balance.

 

Thanks! I'll just buy an internal balanced damper and flex plate from summit. This helped a lot

 

No
Buy one for a 1 pce RMS engine
See post # 4 above
Summit add to the confusion by frequently listing 1 pce flexplates as both internal and external balance
See
http://www.summitracing.com/search/p...rder=Ascending


This one for example is correct for a 1 pce RMS engine
http://www.summitracing.com/parts/fc...make/chevrolet

and you can see it has the balance weight on it that makes some people wrongly call it external balance

 

Ok that makes sense. Yeah summit just emailed me saying to buy a harmonic balancer that is internal balanced but buy a flex plate for a 1 piece that is "external" balance. Thanks so much.

 

It is disappointing that Summit perpetuates the confusion with this "internal/external" stuff.

I also take exception to the use of the term "harmonic balancer". It isn't a "balancer", it's a "damper". Its purpose is not to balance harmonics, its purpose is to dampen harmonics.

 

Ditto.
But I suspect it originates at the manufacturer and Summit /Jegs just upload their supplied details without any further thought

 

on a side note:
most or all your aftermarket parts list for the 406/413/421/427/434/454 small blocks will be internal bal..

 

And just to really confuse people
there are budget 383 stroker crankshafts based on 400 castings that are TRUE external balance and require the 400 style weighted flexplate and dampener

http://www.summitracing.com/parts/es...make/chevrolet

 

ya I just sold a set up. fluid damper and flexplate for ext bal
for the 3.75 stroke 400 crank in the 350 block

stick with the intern bal parts.. lighter wt stuff