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Author Topic:   scat cranks
posted May 17, 2004 08:47 AM
blew up a 383 with a scat (9000 ser) was wondering should I use a 350 balancer and flex plate or a 400 balancer and flex plate. Built a new motor and it vibrates bad with 400 stuff.Old motor was balanced new motor is not. Any help would be great.

Ego Racing
posted May 17, 2004 09:50 AM
Need more info... Was the original 383 internaly or externaly ballanced? How is the new crankshaft ballanced? Are you running a stock or aftermarket ballancer?

posted May 17, 2004 11:30 AM
The engine was sent to the mechine shop with 400 stuff externaly ball i assume. The new crank has never been balanced just right out of the box.have been running new 400 balancers but there about 1 year old. The old motor broke one rod jurnal right off the crank

[This message has been edited by ssymmonds (edited May 17, 2004).]

posted May 17, 2004 12:39 PM
Sounds like it's horribly out of balance. If the new one vibrates badly, it's only a matter of time until it snaps too. If you took all new, or unmatched parts, it doesn't stand a snowballs chance in h$ll of making it through the year.

What kind of rpms is it turning? A badly out of balance motor will tear itself apart in a hurry at race speeds.

posted May 28, 2004 08:05 AM
fyi got motor back from michine shop they said it was 200 gr on one end and 300 gr on the other out of balance he said they have seeen alot of scat cranks not balanced very well so if you buy one make sure you balance it.

posted May 28, 2004 08:12 AM
I thought all Scat stroker cranks required balancing. I think there catalog even has a warning to that effect.

posted May 28, 2004 11:19 PM
it would be best to call scat to check you part number.
our 400 scat crank is internally balanced. the counterweights are larger and "wrap around" the crank further than a standard 400. this allows for more counterweight for different piston/rod combinations.

posted June 05, 2004 08:35 AM
I have a scat crank in my 383. It's internally balanced, but I still had the rotating assembly balanced by my machine shop. At high rpms you don't want flying apart. besides if your spending the money to build a new engine you might as well spend the extra money. You'll spend it anyway when it blows up. I can't afford that. If I blow up I'm done for a long while!

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