M90 and M30 hybrid options

[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.

[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

[LJ851]

Originally Posted by slammin.e28guy

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]

Originally Posted by LJ851

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.

This is exactly what I was wondering!

So the B34 crank would be the same, BUT If I can get my hands on an M90 crank we'd probably be in business? Stroke of 84mm vs 86mm w/B34 crank.

[LJ851]

Originally Posted by slammin.e28guy

This is exactly what I was wondering!

So the B34 crank would be the same, BUT If I can get my hands on an M90 crank we'd probably be in business? Stroke of 84mm vs 86mm w/B34 crank.

I will test the memory of my friend and see what he remembers about the details. I did a lot of consulting during the build but i cant remember.

I have a M90 crank that i prob would sell. My folks still live in D.C. i could deliver if you are semi patient, Maybe.

[slammin.e28]

Originally Posted by LJ851

I will test the memory of my friend and see what he remembers about the details. I did a lot of consulting during the build but i cant remember.

I have a M90 crank that i prob would sell. My folks still live in D.C. i could deliver if you are semi patient, Maybe.

Hmmm....I'm very patient. I've been meaning to get my hands on an M90 crank, but things never line up for me.

[LJ851]

OK. Here are the details on my friends build. M90 block, B35 crank and rods, 94mm VW pistons, stockish B35 head with schrick 284 cam. Thick M90 headgasket ( i remember 1.7mm thin and 2.1mm thick)

The block and the deck were not cut much, the thick headgasket was needed to get piston to head and valve to piston clearance to be (barely) in the safe range. Piston sticks out of the deck 1mm or so. Compression ratio is at 9.0 to 1 ish.

[Good & Tight]

You can port the M90 intake side to match the B35 intake manifold. That's what I did.
Switch to the B35 cam to make the distributor work.




You can make your adjustable cam gear with a rat tail file just open up your original cam gear.



You will have to knock the dowel pin out.

[kronus]

^^ how do you make sure the cam gear doesn't slip? Seems like four small bolts won't hold the angle too well..

Also is this possible for a dual-row chain?

[Good & Tight]

Originally Posted by kronus

^^ how do you make sure the cam gear doesn't slip? Seems like four small bolts won't hold the angle too well..

Also is this possible for a dual-row chain?

I have washers under the allen head bolts, it has never moved. Not sure on a the double row, can't see why you couldn't.

[kronus]

Also, interesting, so this lets you use the M90 head and not lose compression.. do you even need an adjustable cam gear in this case?

[Good & Tight]

Originally Posted by kronus

Also, interesting, so this lets you use the M90 head and not lose compression.. do you even need an adjustable cam gear in this case?

There's HP to be made by adjusting the cam timing. You had mentioned an adjustable gear and wanted to share the info. Doesn't hurt to have it though if you like to tinker with the powerband.
I did it for my turbo set up to adjust exhaust pressure to spool the turbo.

[kronus]

The info is very appreciated, thanks!

[Good & Tight]

Originally Posted by kronus

The info is very appreciated, thanks!

No problem, the cool thing about the M90 is that the bottom end is exactly like the M88.
Stock they put out 218hp & 228ftlbs, great engine. 84mm stroke 93.4 bore.
Plus it has more displacement than the B35... "The M30B35 635 engine has a displacement of 3430 cc while the M90 has 3453cc"

[kronus]

So, do you think Motronic 1.3 cam and intake/injectors/management is better enough than L-Jetronic everything to justify the upgrade? Will I need a Miller MAF/WAR chip or some other piggyback to tune it?