for an 81 Euro spec 635CSi engine. It's a high compression 3453cc (M90B35 instead of M30B34 - special designation because its basically a race car block.
also, will the 735 turbo manifold bolt up to this engine?

Tough to say about the E23 turbo engine, i thought that motor was the M103 and was a different design, closer related to the M30...but i could be full of it. What kind of parts are you looking for? eBay might help some, for the patient ones. the m90 also runs the older the bosch jetronic ecu system i think. parts in general are harder to find, but not impossibel, for the older (E12 based chasis) E24's, as some of the owners here will tell you.

-Jeff

i was just referring to parts in general. Someone has an e30 with this engine in it that they are offering me, so I was just wondering about mantainance

Simple. Phone the dealer, give them a part number, and get what you need.

Al

so parts ARE readily available?
also, how reliable are these engines? are parts expensive?

The old big six engines are very reliable. Parts from the dealer are going to be a little to a lot more expensive than through the forums, eBay, but you have a better chance of getting them in a timely manner.

-Jeff

for an 81 Euro spec 635CSi engine. It's a high compression 3453cc (M90B35 instead of M30B34 - special designation because its basically a race car block.
also, will the 735 turbo manifold bolt up to this engine?
It is a M90, not a M30B35. The 745 manifold should bolt up, since it is a M30 derivative.

The 745i manifold will bolt-on but the studs in the head should be replaced. The head should be redrilled and tapped to accept the larger studs that were used with the turbo motor for the proper bolt up of the manifold.

The main difference between the M90 and M30 is this: M90 has a larger bore and shorter stroke than the M30. The short block is basically what was used for the S38 (they share the same bore and stroke). Some say that a well tuned M90 can give a M6 a run for it's money (don't know). When I get my car together, I'll find out.

The main difference between the M90 and M30 is this: M90 has a larger bore and shorter stroke than the M30. The short block is basically what was used for the S38 (they share the same bore and stroke). Some say that a well tuned M90 can give a M6 a run for it's money (don't know). When I get my car together, I'll find out.

I was chasing Scott Andrews through the hills near San Fran in a Dinan M6, and his M90-635 kept me hopping! I think he's a better driver, but that car was worthy of a lot of respect! Think the E12 Euros are lighter, too, so that helps...

If you want to read a few things Scott has to say about the M90, go to Big Coupe and under engines, I started a thread on "M90 Stroker", read it.

Parts are not hard to find in my opinion. I have solicited a variety of sources, online, local part stores (simple things - belts, brake pads etc ...), and I have watched vigilantly for older sixs people are selling with the intention of parting out.
I have not found anything that I could not locate.

I had a 79 635 years ago, my modifed 79 would play havoc with the M6's at the track. Parts are not a problem, unless you are buying sheet metal, of course that goes for all e24 cars. Let me know if I can help as I have been sourcing parts on e24's for over 20 years now

for an 81 Euro spec 635CSi engine. It's a high compression 3453cc (M90B35 instead of M30B34 - special designation because its basically a race car block.
also, will the 735 turbo manifold bolt up to this engine?

I'm in Germany if you need help getting Euro parts.