engine internals

[King of Cleveland]

There seems to be quite a bit of mis-information regarding engine internals, their year ranges, and their desirability. Specifically:

What year (or part year) exactly is the break between the early 7mgte blocks with the weaker main webbing and the later blocks? Also, are the JDM blocks different than the USDM blocks over that break? did they switch sooner or later?

Are there differences between JDM and USDM blocks in any ways other than the oil squirters? Is one stronger than the other?

There seem to be three different cranks. The later ones with smaller counterweights on all the throws are the more desirable ones, it seems they spin smoother at higher RPM, but some threads indicate two versions of this crank. Can someone sort this out for me? Is one crank significantly lighter than the others? Do the balancers and pressure plates all interchange? (as in: are any of these offset balanced?)

Does anyone have the actual specs for any or all of the cams that came in these motors?

could any of this type of stuff be made into a "general engine info and interchange" type of sticky? On the mopar boards I'm on those types of stickys have helped me tons especially when heading to a yard.

cheers
Ryan

 

[tomanji84]

I can not answer your question... but I would imagine if you call the dealer and ask for part #'s based on year models for the crank.. if the part # is the same then the part is the same if the #'s are differant then I would get all the #'s and look at each one individually.... other than that I have not seen much info posted regarding your questions... I may be wrong though considering I have not been around supras for very long.

 

[IJ.]

2 cranks 6M and 7M

NA blocks changed to the thicker casting before GTE's did but I can't pin either down to specific years.

 

[Burntz]

Do you know the years for the 6m crank?

 

[IJ.]

6m in the first 7M to late 89/90.

 

[drjonez]

2 cranks 6M and 7M

yups.

NA blocks changed to the thicker casting before GTE's did but I can't pin either down to specific years.

yups again. who cares about the GE? no oil squirters! the GTE should have changed over somewhere in '89....but i'd look for a '90+ block just to be sure. there's pix on mkiiitech.com (i think?).

 

[Burntz]

6m in the first 7M to late 89/90.

Ah, so I'd have a 6m crank, but prolly not the better casting as I'm an 86.5. Its good to know what I have at least lol.

 

[IJ.]

Better casting?

Our cranks are forged not cast

 

[drjonez]

the 6M crank is lighter by nearly 8 lbs...IIRC....

 

[IJ.]

Just under 6

 

[drjonez]

gah...i was close!

 

[Nick M]

edit: They were weighed once at 52 and 57 bls.

 

[drjonez]

sounds about right...

 

[pimptrizkit]

edit: They were weighed once at 52 and 57 bls.

mine weighs 49 1/2 :biglaugh:

 

[starscream5000]

You want to be like that eh? Ian, how much does your 7M crank weigh?

 

[King of Cleveland]

so the blocks changed part year in '89? how about JDM blocks? same year? Anyone know if there is an easy way to tell externally, ie in a junkyard?

Are there any strength differences between the two cranks? I don't really see many crank failures mentioned anywhere on the web, I assume either will probably exceed the strength of the bottom end, although at that point it's usually a chicken-or-egg problem when diagnosing shrapnel.

Does the lighter crank rev quicker? 6 lbs. of balance weight should make a bit of a difference.

cam specs? anyone?

 

[drjonez]

geez. read n search.

 

[King of Cleveland]

I have been. There's a ton of conflicting information... This board seems to be less "dood, how do I turn the boost up to 20?" than the other boards, that's why I'm asking here.

I did find cam specs (stock and a few aftermarket) just now, here:

http://users.tpg.com.au/users/loats/index.html

I can't find a straight scoop on the timing of the block change tho, If I know which 89's I can dig for I'll be in better shape.

 

[starscream5000]

Go by visual inspection, they are easy as hell to tell the difference between because the beefiness of the newer blocks and extra ribs on the outside are quite obvious.

 

[3p141592654]

Its all here, along with most everything else M related.

http://www.mkiiitech.com/forums/viewtopic.php?t=923