Billysvette

Can someone explain the external balanced engines,i have not dealt with them before,i bought a 383 kit that was suppose bolt in kit,is a external engine balanced at all internally?or is it the harmonic balancer and fly wheel that balance the engine?the internal engine i know is balanced inside,crank,pistons,rods.

BLOCKMAN

Exteranal would mean you have to run a weighted flywheel and balancer, Never seen a kit yet that was bolt in.

Most kits we have seen the rods are on the tight side or under the low spec if the rods are floated the pin end need to be sized as well and we find most pistons the pin bores need to clearaced as well.

If its a magazine kit take the rotator some where and have it balanced.

If its a cast Eagle make the snout is up to size as a custome brought in an Eagle that the snout was to small and you could push the balancer by hand and the second one was the same and finally Summit sent him a Scat and that one was fine.

Personally I would not run an exteranlly balanced crank as there has been a lot of breakage problems with them on the snout.

http://www.pacificp.com/forum/viewto...8d105315551ca3

http://www.ls1tech.com/forums/small-...-my-383-a.html

Billysvette

The kit i got was a eagle kit which they had already clearanced the crank and rods.

WPaul400C6

since 383s usually run a 400 crank, you need an externally balanced 400 flexplate and an externally balanced 400 harmonic balancer. I've had both types of engines before, never experienced any negatives on either. As I understood it the 400 and 454s had to be built externally at the time but thats somethng a builder once told me. get yourself that flexplate and balancer then you'll be ready to start enjoying the fun

Ganey

Yes 400 & 454 - only a small part of the balance is external.

glen242

You can purchase internally balanced 383 stroker kits/cranks both from Eagle or Scat.

I have one!

Given a choice, I would go with an internal balance set up.

BLOCKMAN

I would have it checked put as I have seen their kits and the salesman will tell you anything to get a sale!!!!

FRSTR90

Small part? It took me 7 slugs of mallory metal and $800 to get a shop to internally balance a 454 crank!

BLOCKMAN

Thats cheap!!

Billysvette

What im having with this engine and it runs great by the way,Is at cruiseing speed my engine will shake where as my other engines didnot,they were internally balanced.The only thing i changed in the kit was the flywheel because i have a stick and the flywheel they sent was for a automatic,so i bought a aluminum flywheel that was for 383,400 engines external balance engines.Maybe i should have had it check out before putting it in.

BLOCKMAN

I have rebalanced a few of the prebalanced assemblies one was off 32 grams on one end and the kits came with the pistons still in their sealed packages and the pistons were still sealed in their boxes, I never figured out how the assemble got balacned when notheing was taken out of the packages.

Externally balaced asemblies are the worst ones as no one knows what as put on each end of the crank when it was balanced.

We have only used internally balanced rotators and that way any neutral balancer and flywheel with work and we also can balance the Pressure plate as well after we balance the flywheel.

Sounds like one of those budget kits as we have a customer bring in a Eagle kit the pistons were off 8 grams and where do you take 8 grams of an aluminum piston.

After 2 Eagle cast cranks were junk because the snouts were under size Summit sent a Scat one and it worked fine.

My own builds I will not use cast cranks period as we see to many other guys having problems with them and and we use no hyper pistons either.

MotorHead

If you change flywheels you can't just put on another flywheel or flexplate with balancing the entire assembly or do what I did.

I sold my 406ci with externally balance crank with a flywheel. He took the flywheel to a shop and had a flexplate balanced to match the flywheel. He had no vibration problems. That is what you have to do.

Billysvette

Thanks,i guess i will take out the motor again

MotorHead

I meant to say without balancing the entire assembly

Good luck, a little work but you always end up fixing or upgrading something else in this process

Billysvette

I now ,but i just upgraded everything this summer,everything is new performance parts Wife isnt going to like this,me taking it all apart again

MotorHead

If they sent you a flexplate for an automatic and a harmonic balancer then there is a possibility they balanced the assembly. Phone the seller and ask.

Before you tear the motor apart, drop the tranny, take your flywheel off get an externally balanced 400ci flywheel and have that matched to the balance of the flexplate they sent you and you should be fine, provided the entire assembly was balanced in the first place.

If you can't get an answer on the balancing I would still try what I said provided you still have the flexplate that came with the assembly. Much easier than tearing the motor down, that's like rebuilding it almost

MotorHead

One more thing, in the good old days in good shops the balancing on an externally balanced engine was done on parts inside the motor, crank, rods pistons whatever to get it balance without touching the harmonic balancer or flywheel. Hack jobs will drill holes in the flywheel or tack on weight.

Before the Chinese started making "performace parts" you had only a few parts companies that supplied good high performance flywheels and balancers. What the smart shops would do would balance an externally balanced engine to good and popular GM flywheels and harmonic balancers.

They did not touch these parts so if you needed a new flywheel you just ordered the same flywheel, no balancing involved.

If you can't find the flexplate, dump that aluminum flywheel ( that's causing the problems IMHO ) and get a good steel GM or Hayes flywheel for a 400ci and just try that.

MotorHead

........and one more thing, if it was never balanced in the first place, your screwed

kurt81

I agree, I also picked up an ex. balanced 383 rotating assembly that is Eagle crank and speed pro pistons. The kit came with a flexplate and balancer, but also came with the balance sheet they used when it was balanced. I took the entire kit to my machinist and it all checked out. You should have recieved a balance sheet with the kit, if you didn't, it may not be balanced. Good luck and I hope you find an easy solution.

Billysvette

Thanks guys,Motorhead i will do what you say after i check to see if it was balanced,i hope it was,but isnt it hard to drop a manual trans because of the cross member ,not able to take it out like the autos?Or can i do it with ease?