6M Crank

[Jeff Lange]

Hardly JZ-style though, lol.

1JZ is 71.5mm stroke... that's F***ING short! Shortest stroke of any Toyota engine I know of.

 

[Toycoma]

what year is your engines ECU?

its a 90 so i guess the ecu is as well. the car was an automatic and now it has a manual. i have an 88 ecu for a manual supra in my garage but never looked to see if it would plug into the cressidas harness. thing it would change anything if it plugs in?

 

[Toycoma]

Here are a few pics. The newer (silver) crank is a 7M crank. Which is the crank I stroked because of its added balance. The other is a 6M crank, the pics are okay. You should be able to se the differences.

is the crank done in these pictures? if so, why didnt you get it knife-edged?

 

[DEFIANT 7M]

is the crank done in these pictures? if so, why didnt you get it knife-edged?

Yes...Thought about it, but just did not see the need.

 

[DEFIANT 7M]

This the best explaination of the 6M/7M cranks.
http://www.jblmk3.com/id145.htm

 

[flubyux2]

the 6M and 7M are both balanced... i dont know why dude man said that the one is fully balanced and the other isnt..the 7M has double counterweights to smooth out the harmonic vibrations over the 6M crank. the 6M crank is something like 9 or 10lbs lighter than the 7M gimmick. some early 89's had 6M cranks. the one from the early 89 supra i did a 1j swap on had the 6m crank in it.

 

[Halsupramk3]

The 6m crank is 5 lbs lighter from not haveing any counter balance weights on the #2 and #5 journals. I would think toyota put balance weights on those journals to help completely balance the crank. I would think that those extra two balance weights absorb vibrations.

I had my entire rotating assembly balanced from HB to flywheel and pistons etc. The shop did remove some material from the crank. Not much but it did make it more balanced. I think toyota balances the crank much bette than most manufacturers. I do not know how much more was removed from mine but it wasnt but a few divits.

 

[Jeff Lange]

the 6M and 7M are both balanced... i dont know why dude man said that the one is fully balanced and the other isnt..the 7M has double counterweights to smooth out the harmonic vibrations over the 6M crank. the 6M crank is something like 9 or 10lbs lighter than the 7M gimmick. some early 89's had 6M cranks. the one from the early 89 supra i did a 1j swap on had the 6m crank in it.

It's not that the 6M isn't balanced, it is. It's just not fully counter-balanced. It has no counter-balances on the 2nd and 5th cylinder, where as the 7M is fully counter-balanced, with counter-balances on every cylinder.

If you notice, when I said which years had what I included 89 in both. Some 89's have the 7M, some have the 6M, I've seen both in 89 models made both in early 89 and in late 89.

 

[suprra_girl]

rev limiter on the 6m cranks = 6750

silly auto.. should get that paddle shifter kit

 

[flubyux2]

exactly right jeffery. the 89 with square motor mounts are almost guaranteed to have the 6m cranks. the late 89's with the newer round mounts are almost guaranteed to have the 7M cranks.

and yeah, both cranks are balanced, but not completely COUNTER balanced. the 7M is just supposed to run smoother with less NVH... thats it.

 

[Jeff Lange]

exactly right jeffery. the 89 with square motor mounts are almost guaranteed to have the 6m cranks. the late 89's with the newer round mounts are almost guaranteed to have the 7M cranks.

and yeah, both cranks are balanced, but not completely COUNTER balanced. the 7M is just supposed to run smoother with less NVH... thats it.

My name is Jeffrey, not Jeffery.

 

[flubyux2]

gotcha, K-man.... or should i call you Cosmo!

 

[james_9876]

I'm glad someone posted about this, I'm the third owner of a 88 mkIII and I know the last owner had a junkyard motor put in, I kinda freaked out when I saw 6m on the crank while reassembling the mains, and rod bearings. And now I can sleep better at night knowing this thread clears it all up.

Thanks guys!!