6M crank or 7M crank?

hvyman

Dang Dude! No Way Man.
Staff member
Apr 17, 2007
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Fullerton,CA
6m is lighter and the 7m is better balanced.

so you can either balance the 6m which will lighten it a tad more or lighten and re balance the 7m.
 

HommerSimpson

New Member
Dec 31, 2007
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New Smyrna Beach Florida
7m is fully counterweighted so its smoother.. but weighs more.. so taking the 7m and having it shaved and rebalanced is the best .. but cost a ton..
so imho eather or stock will work fine.. if you want little more rpm go with the 6m if you want a smoother engine thats easyer on the bottom end go with 7m
 

SupraJerry

Banned
Jun 23, 2009
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Kilgore
CajunKenny;1380748 said:
Toss them both and stick a Chev 350 crank in there. You'll get more compression.

j/k

How do you strech the cheezy (sorry, I meant 'chevy') crank to fit?
It is too short for a 7M block.

If you have personally done that, I for one would love to see pictures.

Now on the 7M vs. 6M,
I just seen a post by IJ a few weeks ago on the subject,
sounds like he has the most experience on this.
 

IJ.

Grumpy Old Man
Mar 30, 2005
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I come from a land down under
hvyman;1381000 said:
^yup.

just take a 6m crank and have it full counter balanced. light and balanced.

7M crank is fully counterweighted.....they're ALL balanced, look at a 6M you'll see missing counterweights on a couple of the throws, to compensate others are larger/longer so it's never going to be as smooth running as a 7M crank.

crank01.jpg


crank02.jpg


crank03.jpg
 

black89t

boost'en down 101
Oct 27, 2007
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humboldt, ca
i have a 7m crank motor and a 6m crank motor. the 7m crank motor is what i'm driving now. really the difference in how they drive is hard to even notice...