Internal vs external balancing
Thread Starter
Instructor
Joined: Jun 2005
Posts: 156
Likes: 0
From: Liverpool NY
Internal vs external balancing
I'm going to be shopping for a 383 short block and am not clear on the internal vs external balancing. this is going in an 82 with a 700R4 tranny.
Can anyone explain this to me?
Can anyone explain this to me?
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Externally balanced uses a counterweighted flywheel and damper to balance the assembly. I would much prefer an internally balanced engine
Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
Go for an internally balanced engine.
I orderred my crate engine (externally balanced) with a flexplate, as I intended to use an auto.
I then changed tack, and bought and installed a 5sp manual, and had to use an externally balanced flywheel. I had issues with vibrations even though I used the appropriate flywheel with the offset mass. I've had the flywheel "matched" to the flex plate, and most of the vibration has gone, but it just would have been so much easier if engine was neutrally balanced from the buildup...
I orderred my crate engine (externally balanced) with a flexplate, as I intended to use an auto.
I then changed tack, and bought and installed a 5sp manual, and had to use an externally balanced flywheel. I had issues with vibrations even though I used the appropriate flywheel with the offset mass. I've had the flywheel "matched" to the flex plate, and most of the vibration has gone, but it just would have been so much easier if engine was neutrally balanced from the buildup...
Melting Slicks
Joined: Mar 1999
Posts: 3,027
Likes: 137
From: Nashville TN area
take the crank, pistons and rods and have everything balanced as an internally balanced rotating assembly. then zero balance your flywheel and pressure plate, as well as the front balancer/hub.
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
If you are using a 400 crank, then internal balancing may cost you a chunk of change, if the crank you are using is an internal balanced crank, then forget what I said...
Drifting
Joined: Aug 2004
Posts: 1,883
Likes: 124
From: Lubbock TX
It depends on intended usage as much as anything. If you're not going to race it or rev it over about 6 grand, save the money from internal balancing and use it on something else. GM built tons of 454's, all externally balanced, and I've never seen a balance related issue. Where a good shop gets balance within about 1/2 gram, GM was good to get it to within about 1/2 ounce. If you're going to beat on it, by all means, have it internally balanced.
Racer
Joined: Sep 2003
Posts: 258
Likes: 1
From: Memphis TN
I went through this issue on my 454 build. As has been already stated, 454's were all externally balanced from the factory, as were 400 small blocks. Your lower priced (cast steel) big block cranks are externally balanced but the forged 4340 stuff are mostly internally balanced. It's the same story for 400 cranks used in 383 small blocks. My Eagle 4340 forged crank is internally balanced and I really like it. My 454 really likes to rev and has no vibration at 5500-6K. Internal is the hot setup if you can spring for it.
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