M90 and M30 hybrid options

[LJ851]

I have done much research along these lines.


Always wanted to slam an M30 block out to 94mm, run flat top VW pistons, M90 head (maybe bigger valves for lulz), crank, cam (maybe go hotter on the cam), E21 manifolds.

I've got an 83 M90 head and a few B34 blocks laying around. VW pistons are cheap cheap cheap. Trying to find my thread on this combo on Mye28 as we speak.

My buddy built one although it hasn't run yet. I don't think he would do it that way again. The VW pistons protrude quite a bit over the deck with the B35 crank and valve to piston clearance is very tight.

[slammin.e28]

Forgive me, I wasn't as "into" these cars as I am now. I was still young. Gave up on that idea when I scored a B35 for cheaps and slammed it into my e28, thus ended thread.

Slammin's M90/VW/M30 WTF thread

[slammin.e28]

I have done much research along these lines.


Always wanted to slam an M30 block out to 94mm, run flat top VW pistons, M90 head (maybe bigger valves for lulz), crank, cam (maybe go hotter on the cam), E21 manifolds.

I've got an 83 M90 head and a few B34 blocks laying around. VW pistons are cheap cheap cheap. Trying to find my thread on this combo on Mye28 as we speak.

[chadthestampede]

What about the b35 block with the m90 head, m1.3, runners from an e21 and bananafold for cool factor? That will give you higher compression than anything else I believe.

http://www.firstfives.org/faq/e21_intake/320_runners.html

EDIT: Ah. I just saw that you said your b35 crank is damaged. Carry on.

[LJ851]

awesome: http://www.mye28.com/viewtopic.php?t...ion+calculator

Sounds cool, cant seem to open it on my computer?

[kronus]

awesome: http://www.mye28.com/viewtopic.php?t...ion+calculator

[kronus]

Great, thanks for the info.

[LJ851]

That's a good question. How would I measure that?

I would work with the heads loose. You will need a burette with some light oil and a small piece of glass or plexiglass. Its pretty simple to do, i'm sure you can find a writeup on cc ing a head online.

Once you know the difference you can calculate how much you will need to cut to remove the unwanted cc's. On a head with a chamber that is basically round this is pretty simple as it's easy calculate the volume of the cylinder of space removed.

[kronus]

Can you cut the B35 head enough to get the cc down to M90 numbers and retain the compression ratio? Remember to check valve to piston clearance, the valves are getting closer to the piston by the same amount you cut (plus the larger B35 valve).

That's a good question. How would I measure that? Some sort of bolt-it-up-with-clay-and-do-a-rotation to check the clearance, but not sure how to figure out how much to deck the head, and I haven't found anyone who's done it.

[LJ851]

Can you cut the B35 head enough to get the cc down to M90 numbers and retain the compression ratio? Remember to check valve to piston clearance, the valves are getting closer to the piston by the same amount you cut (plus the larger B35 valve).

My M90 flys are pretty light, 14 lbs iirc.

I think you are on the right path, i would go all B35 if it will clear and you can get the compression back up. More potential for a better tune.

[kronus]

Also, the main advantage of the B35 manifold would be the more modern injectors and electronics. I think I'll end up using whatever management came stock for the head casting I end up using, so I guess the concrete question is, stock M90 head + L-Jet or shaved M30B35 head + adjustable cam gear + Motronic 1.3?

I'd venture that a lot of the throttle response comes from the much lighter flywheel. All B35s came with bigass dual-mass flywheels that weigh 20+ lbs, but I think the M90 came with something a lot smaller and more reasonable.

[LJ851]

I thought the B35 cam and stock M90 cam were pretty equal, and the B32 cam was a bit hotter?

I think you would be spitting hairs with the best of the stock M30 cams. Aftermarket is the way to go for more power. I think L jet is more forgiving of a more aggressive cam than motronic btw. Overlap puts motronics panties in a bunch.

[kronus]

I thought the B35 cam and stock M90 cam were pretty equal, and the B32 cam was a bit hotter?

[LJ851]

There is nothing wrong with L jet in my book if it runs well. Motronic would improve your fuel mileage but i have never drooled over motronic throttle response on any engine.

The M90 intake works very well and you can substitute E21 bananas for more volume/flow if you desire. The B35 cam is about the best stock cam and i think you can still buy the conversion nut to drive the distributor from MM.

I would try to keep the compression up in the high 9's or so if you can. A standalone ecu controlled M90 would be ideal for your situation.

[dannyyisntt]

This is relevant to my interests.