6m or 7m crank

[Insidious Surmiser]

is there any way to tell which one i have (swapped 89 jdm gte motor) i have a thing about sticking w/ factory recomendations :icon_bigg

 

[Superjustin13]

Depends on what year the car was made, some 89early dont have it late 89's do also 7m cranks are more counter balanced on #2/5 cylinder, hence the 6250redline. yeaa..

 

[spoolint78]

it should be stamped on the crank
6m or 7m

 

[Insidious Surmiser]

would i be able to tell by pulling the pan off?

 

[mickyg]

Yes. The stamp should be fairly easy to see and if you can't find anything obvious, try rotating the crank.

But it's probably easier just to see if the counterweights are there. They're fairly obvious. The 7m is fully counterweighted and the 6m is not.

 

[IJ.]

Only the 6M crank has an ID mark.

Top 7M crank Bottom 6M

 

[mickyg]

Thanks! I was just about to suggest they look at your pics.

 

[Allan_MA70]

You better not have a 7m crank in that motor of yours micky!

 

[Blackmk3]

whats is the perks and downfalls of a 7m or a 6m crank? ive gotta 6m crank i was going to use on my rebuild and as far as i can learn 6ms just arnt as counterweighted? is that true...i mean ill get it all balanced up anyways

or is there other reasons that make the 6m crank perferable to the 7m crank or oppisatly

(sorry about the spelling)

Thanks
Nick

 

[IJ.]

7M is smoother.

 

[mickyg]

You better not have a 7m crank in that motor of yours micky!

You had it long enough to check so it's your own fault!

Seriously though, I doubt it's got a 7m as the motor's likely a 87 or 88. Unless someone got a replacement crank for it along the way.