Scat makes a nice internally balanced 3.75 stroke cast crank ( 9000 series ) it is the same price as the externaly balanced one 
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External balancing
Thread Starter
Racer
Joined: May 2005
Posts: 470
Likes: 1
From: Amelia Ohio
External balancing
What is the difference between that and internal. I just ordered my 383 stroker assembly and I was told it has to be externally balanced. Speedway Motors is doing the balancing and it comes with the harmonic balancer and balance plate which is another thing I'm unfamiliar with. This is my first stroker so I am treading into different waters here. Any input will be appreciated.
Chris
Chris
Drifting
Joined: Sep 2004
Posts: 1,959
Likes: 1
From: North Bend Ohio
The 400 Small Blocks and the 454 Big Blocks are externally balanced from the factory. All other stock engines are internally balanced. There is not enough room in the crankcase for larger counter weights to balance the longer stroke crankshafts. So the counter weights are made a little small and weight is added to the flywheel/flexplate and the harmonic balancer.
These crankshafts can be internally balanced by using heavy metal slugs in the counter weights but this can run into some money.
BigBlockk
Later.....
These crankshafts can be internally balanced by using heavy metal slugs in the counter weights but this can run into some money.
BigBlockk
Later.....
Team Owner
Joined: Oct 2004
Posts: 23,831
Likes: 10
From: Springfield MO
St. Jude Donor '07
I have an internally balanced forged crankshaft for a 400 SBC. It can be done, but it isn't cheap. It's the only one I've seen, I got it from a guy who decided not to build his 400. He got it from a race shop in Michigan or something.
NCM Grand Opening Veteran
Joined: Sep 2005
Posts: 20,979
Likes: 384
From: South of giving a damn
St. Jude Donor '11, '17
It's nothing to be concerned about. You just have to remember that the harmonic balancer & flexplate/flywheel are for 400ci SBC, nothing else is different. You are past the decision point, as far as the internal/external balance question is concerned. Most 383s are externally balanced, as I'm Batman stated it costs more for internal balance.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
the more you spend on balancing parts the smoother the car will run.....externally balanced puts all the weight at the end of the cranks shaft to smooth out the imbalances.....internally balanced puts the "corrections" right at the spot where its needed.... you need to pick up a book on building engines and balancing them, it will be well worth the $20
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Balancing
Originally Posted by evalu8r
What is the difference between that and internal. I just ordered my 383 stroker assembly and I was told it has to be externally balanced. Speedway Motors is doing the balancing and it comes with the harmonic balancer and balance plate which is another thing I'm unfamiliar with. This is my first stroker so I am treading into different waters here. Any input will be appreciated.
Chris
Chris
P.S. We do no more external balance jobs unless it's a restoration where the vehicle has to look original. 383's, 400's, 454's, 509's, and 540's ALL get internally balanced!
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