SDPC Tech Tips: Internal vs External Balance

[@16vSciroccoboi]

Neutral balance balancer is a harmonic damper then and not a balancer at all. Calling it a balancer when it's a non counterweight damper I believe causes more confusion than anything.

[@bigredracer7848]

2👍's up SD thanks again for having us all along with you for the rest of the story

[@El91637]

Thanks for the clear explanation. I have a 1985 GM 4.3L V6 (2 piece rear main seal) in my garage that I want to mate up to a manual trans. The flex plate that came with the 4.3 has no weight on it. Now I know I can source a flywheel from a 1985 or older small block with a manual trans and go with it.

[@ronpetrosky1814]

Would putting the pressure plate on in a different position cause a vibration ?? 4 speed AMC T-10 externally balanced. Thanks for your help

[@mightyeagle]

Your very good at getting to the point thanks

[@christopherkanuk2546]

Thank you so much not confused anymore

[@warrenlucier5796]

This question pertains to the SBF as they went from a 28 oz. to 50 oz. and why can't the assembly just be zero balanced? I realize you were explaining SBC for your customers, but all of this pertains to all 3 manufactures that have a similar design.

[@TheComputerArmory]

Long story short, rebuilt 700r4 all new sonnax parts, replaced factory flexplate as two welds were cracked, have since put 3 flexplates and still have a vibration and have also replaced TQ convertor twice. Old flexplate "weight" best i can measure weighs 2.19lb, new flexplate weight weighs 2.32lb nearly a full 2oz or more over factory. Can this be causing my vibration? Vibration occurs during all RPM and in Park, Neutral and all others, ranges from 600-6000rpm, very bad at 1200 and 4000. How i measured was laying flexplate flat on a scale and a box that was simular hight and a 50/50 weight distribution on the scale and the box the best i could.

[@frederickshipp8013]

I know someone who ran a 427 flywheel on a 454 and was going through main bearings all the time until he found out what was causing the problem. (Flywheel)

[@stevesteve7373]

So if I need to swap flywheel from 1 piece to 2 piece crank, my 10.5 clutch will still bolt up ok? And starter should fine as well? Just the mounting to crank changed?

[@MariusSalvetti]

Technically, there are no internally balanced 350's from the factory. the 2 piece crank 350's had an external "wing" that was part of the crankshaft. The 1 piece crank 350's could not use the external "wing" because of the 1 piece seal design. Chevrolet had no choice but to add the required weight to the flywheel or flexplate.

[@CzechSixTv]

Integrally balanced might be a more accurate description for the 2 piece seal crank.

[@MariusSalvetti]

Yes, that is much more accurate. If gm would have used a little lighter piston they could have internally balanced them.

[@CzechSixTv]

@@MariusSalvetti The real issue is that the block was never meant to house that much stroke. It was originally designed for a 3" stroke 265 that had a round flywheel flange. Just going to slightly larger pistons in the 283 required notching the flywheel flange for balance.

[@joneich1591]

I have a 1 piece seal 350/5.7 chevy that I am rebuilding. Would it benefit me to internally balance this motor, then balance it again with the flexplate and harmonic balance?

[@ussj4brolli]

To note - this is incorrect for the LT1 in a 95 Camaro, regarding the 383. For example, when making it a 383 using an eagle crank that is internally balanced, you need a zero balance flywheel.

[@CzechSixTv]

It's a video from a Chevy dealer. He's talking about when guys would cut O.E.M. 400 cranks down to 350 mains and the cranks used in current GM's 383 crate motors. There are other 1 & 2 piece seal stroker cranks from the aftermarket that are internally balanced as well. With enough Mallory metal($$$) any crank can be internally balanced but for assembly line motors external is easier for the longer stroke.

[@timmygun1]

Question are marine 383 vortec external engines. Internal or external? Please help

[@adamgarcia1824]

Can I use a normal four-speed standard flywheel for a internal balance 400 small block

[@Timmyboy2]

Does the engine block set the internal versus external, one-piece versus two-piece application? I'm looking at a used 400 SBC block

[@CzechSixTv]

All 400's used a 2 piece rear main seal and factory external balancing. There are conversions to fit small block 2 piece seal cranks into 1 piece seal blocks, originally developed to fit cut down 400 cranks into newer blocks when building a 383, but none the other way around. If you've got a 2 piece seal block, you need a 2 piece seal crank.

[@MauricioHernandez-st8su]

Hi. Good information. I have a question. I bought a 350 vortec one piece. The motor was on truck with std transmission,. Can i use flex plate for automatic transmission??? Thanks.

[@Sdpartscenter]

Yes, you can bolt a flexplate in place of the flywheel. No issue there.

[@josephacevedo9325]

I have a 1973 400 sbc that’s in my 74 c10 I bought this from a friend but he dnt knw anything about the previous work on it. So I’m asking if you know or can point me in a directions if that year was internally or externally? It is a two piece rear main came with a 400 externally 168 flexplate but had a balancing plate? Is this needed or is it wrong and just needs a internally balanced flex plate?

[@josephacevedo9325]

And also has a bad vibration at low rpm’s 🤷🏽‍♂️🤦🏽‍♂️

[@Kellengravesfab]

External balance

[@sharons9367]

I’ve got a 350 one piece rear main marine engine , it’s got a flywheel on it I did notice it was drilled out when rebuilt, I did question engine builder when replacing balancer they said neutral or internal balancer will be fine ? I just don’t know whether to believe them Help please

[@Sdpartscenter]

One piece real main seal small block came from the factory with an external balance flywheel or flexplate and a neutral/internal balancer.

[@sharons9367]

@@Sdpartscenter apologies it’s two piece rear main

[@thomaslockley945]

There is no external Ballance 350

[@ratgasgarage]

Can I take a early sbc flywheel /clutch and install it on a mark4 bbc

[@Sdpartscenter]

Yes, the flywheel and clutch off a 2pc rear main seal SBC will fit an internally balanced BBC.

[@dalestogdon839]

Does a 383 crank. Use the stock dampener bolt. On holding in balancer

[@Sdpartscenter]

Yes, it does.

[@dalestogdon839]

Mine is like 1/2 bolt. Is a big block balancer bolt. It be bigger then 350 chevy

[@dalestogdon839]

I'm having truble. Spent grip of money on her Balancer given me a hard time. Take it to the builder. Let him fk it up. At least then I can tell at someone. Lol

[@LemonmilkMusic]

I have a 383 that was “blueprinted” and balanced by a shop before he sold the car 67 Camaro. I have a noticeable difference in the feel of the engine between 25-2800 rpm. It’s worst if I cruise in that range but hardly noticeable if I’m powering through that range Does that sound like an engine balance thing or could it be something more simple. Like a plug not functioning fully,? gap being off slightly ? A valve adjustment thing? It runs really good otherwise. It’s got the Holley sniper EFI and Hyperspark ignition. We have new poly mounts I feel it more in the shifter (Muncie M21). Never driven older cars before buying this so I have no reference on how it’s supposed to feel.

[@jsteganius6969]

@@LemonmilkMusic that does sound like a slightly out of balance thing. It should be smooth all the way through the rpm range. Probably why they sold it because its not gonna be that easy to fix.

[@joe-hp4nk]

What did he say?

[@chrismoher5444]

I want to.build a perfect balance 302. But I think that it would.weaken the crank

[@CzechSixTv]

If it doesn't have weights, it's not a "balancer". It's a damper.

[@vegetaroux6898]

It's basic if your dad taught you. Boarding school teaches nothing

[@beakittelscherz5419]

I came over from "Low buck Garage" to figure out what he is talking about and not to present myself as a Little idiot in the comment section over there...😂Thanks for the Video. Much appreciated Low Buck Garage kzbin.info/www/bejne/sKTHaZJ5ed2ShNE