Question on 360 crank balance

[Hiddentower62]

Hey guys, just got my 360la crank back from the local machine shop, he said I needed a neutral balance converter. When I brought all the parts in to get the crank balanced I brought a b&m 10236 and a stock flex plate and he said to use the stock flex plate with a neutral balance converter. I was just wondering if that sounded right or not. I thought with an external balance engine you needed counterweights at both ends. He also told me the end balanced out at 3g and the front balanced out at 52g, whatever that means. And to answer any questions I just had him balance the crank with new rods and Pistons and yes it's still externally balanced.

 

[Professor Fate]

No. No, no, no, no! If it's still the factory LA 360 external balance, then you need the factory 360 balance weight on the convertor with the factory flexplate (notice how all things I mentioned are "factory"?). If you use a non-360 (internal/neutral balance) convertor, THEN you need the B&M flexplate. The one you mentioned is for a 727, a 10239 would be for a 904.
You sure this guy has dealt with Mopars before?

 

[Professor Fate]

Oh, and welcome to the site!

 

[brian6pac]

I had a 400 Chevy SB with a Scat 9000 crank Internal balanced on the front and external balanced on the rear. It made no sense to me why but that is the way it was.

 

[Rat Bastid]

I had a 400 Chevy SB with a Scat 9000 crank Internal balanced on the front and external balanced on the rear. It made no sense to me why but that is the way it was.

They could get enough weight in the front counterweights but not on the rears. Somewhat common on 4.25 and longer stroke BBC chevy cranks.

 

[Max1196]

he said I needed a neutral balance converter. he said to use the stock flex plate with a neutral balance converter. He also told me the end balanced out at 3g and the front balanced out at 52g, I just had him balance the crank with new rods and Pistons and yes it's still externally balanced.

There's a lot of missing information here. What con rod and what piston was used? Were they considerably lighter than stock? Yes the front or rear of a crank could require a considerable differance in weight correction. Was "heavy metal" used in the ballance job? Post the blue print of the ballance job and perhaps we (fabo) can help you interpert what the machine shop guy prepared for you.

 

[MOPAROFFICIAL]

You can use an externally balanced converter like stock 360's 'especially with stock replace parts/piston weights'...with neutral flex plate like stock.....or you can use an externally balanced flex plate..like the one from b&m and a neutral converter.

 

[Oldmanmopar]

If the builder told you a neutral balance converter and flex plate that is what you'll use. When balancing a 360 crank it is common to balance it with the damper you gave him. So the front of the crank stays the same unless you gave him a neutral damper. The rear rear of the crank will be neutral unless you gave him a 360 flywheel.

We just did a refresh on a 360 with a neutral balance crank in the rear. You should have given the builder a new neutral damper. If you look at the rear counterweight on the crank you will see a slug of heavy metal inserted. 3 grams out at the rear is good for a mild build. Anything above 7000 rpm's should be closer to zero. Scat pro balanced stroker crank kits are terrible we have seen them 18 grams out on some BB fords. Always balance every motor.

You'll be ok listen to the builder.