stroked377

i bought a motor that is ballanced i am not sure what to do because i need to use a different flywheel and it has no ballancer the flywheel that is on it has a bunch of little drill holes on one side on the face of it how do i go about getting the right stuff for it ?

Apeiron

Ask whoever did the balancing whether it's internally or externally balanced.

jcb999

There are also a couple of other rules of thumb. Depending on the piston and rod weight, It could likely be internally balanced without a lot of heavy metal but otherwise, you should be able to look at the crank and see if it is internally balanced. It will have weight added on the counterweight. If its an aftermarket flywheel, lots of drill holes are not out of the ordinary. Are the rods stock?

stroked377

the crank does have little round slugs welded into it with different numbers on them so the crank has been ballanced. this means it is internally ballanced right ? and if this is the case do i just need nuetrally ballanced flywheel and ballancer ?

AlkyIROC

Balancing a rotating assembly has nothing to do with the crank being internally or externally balanced. They are 2 different types of balance. The slugs welded into the counterweights are for recipricating balance. This balances out the weight of the rods, pistons etc. There's no way to change an externally balanced crank to internally balanced. You just can't add the amount of weight needed in the area it's needed.

An assembly can be completely balanced but if it's an externally balanced crank, you still need an externally balanced dampener and flexplate/flywheel. If it's an internally balanced crank (good aftermarket) then a neutrally balanced dampener and flexplate/flywheel can be used.

My engine is internally balanced. I also sent out my flexplate with the balancing and it was 10gm off so even an internally balanced engine should have the neutrally balanced dampener and flexplate/flywheel sent out when balanced.

The only way to know what balancer to use is to find out if the crank is internally or externally balanced. All factory 400 cranks machined down to make a 383 are externally balanced so only an aftermarket crank can be internally balanced but not all aftermarket cranks are.

stroked377

so what do i do if it is already assembled and ballanced and it is externally ballanced do i have to take it appart again to have a ballancer ballanced for it ? cause i have the flywheel for it but i need to use a different one and on the flywheel it has a bunch of numbers like the ballance of it please point me in the right direction

jcb999

You dont have to have it balanaced with the exact rotating parts but it is better ( they dont change the weight of the balancer - they just spin it all together ). An externally balanced harmonic balancer will work ok. Get one of these if your flywheel is internally balanced and you dont want to buy another.


400 Balance Plate/offset

AlkyIROC

Internal and external balance refers to the counterweights on the crankshaft. The 400 SBC and 454+ BBC are externally balanced from the factory. When the factory produced these engines, they felt there wasn't enough room inside the engine for all the mass required for the counterweights because of the longer strokes. They solved this problem by moving some of the weight to the outside on the balancer and flexplat/flywheel. Aftermarket cranks are available with better casting and are able to add an extra counterweight inside the engine to make it a neutrally balanced crank.

When you get an engine balanced, the machine shop is adjusting the weight of the throws to balance out the weight of the con rods, pistons, rod bearings, rings etc. It has nothing to do with the crank being internal or externally balanced. Whenever an engine is built with aftermarket or mixed and matched rotating assembly parts, it should be balanced. 100gm off on piston weight can make a big difference on how smooth an engine runs.

If the flywheel you have came with the engine, you have to assume it's going to be correct. Around the edge of the flywheel will be entirely smooth for a neutrally balance or there will be a notch cut out or a weight added on if it's externally balanced. If it's neutrally balanced, buy any balancer you like designed for a 350.

stroked377

i guess what i am trying to figure out is if it is internal or externally ballanced. It has some metal slugs welded into the crankshaft with different numbers and letters on it. so what is it ?

jcb999

It sounds (to me) that someone internally balanaced your combination. Especially if the flywheel that you have does not have a balanace weight. I would try to either get an internally balanaced harmonic bal that someone will let you return if it is not correct. Or borrow one to start it up and make sure. Id say thats your only option here.

Firebird1986

Irocs are dumb.