Which swap is right for me??

[85e325]

If I may hijack for a sec... according to the interwebs both the B34 and B35 are 3.4L, is this correct?

85e325, if I were you I'd start as early as possible trying to find a nice M30. The B34 was last make in ~1988, so it'll take a while to find one that hasn't been to pluto and back. Unless you're 100% certain of the maintenance history, I'd be giving it a freshen up (gaskets etc) before throwing it in.

That is my intention, I plan on picking up a motor sometime over the summer and rebuild it then swap it next winter once I have all the parts collected.
On a different note, has anybody done any head work to their M30 and noticed any substantal gains? When I rebuild the motor, Im thinking about port and polishing the head and intake as well as doing a 5 angle valve job. One other mod that I was looking at was water-meth injection. Any thoughts??

[85e325]

Since the S38 is losely based off the M30 block, will the S38 intake fit the stock M30 head and would I see any more HP from it? I like the look of the S38 intake a lot better.

[e46s54dr]

The s38 heads are dual cam so they have a totaly different casting. You can either buy and adapter plate to mount them, or swap the whole s38 head on your block.

The S38 head will physically fit the block, but the differences in the S38 block and the M30 block will then manifest themselves...ie

oil drain at the back of the head
timing chain cover differences
timing chain tensioner differences
The sprocket on the crank
the water pump

[85e325]

I figured that swapping the s38 head wouldn't be an easy straight-forward ordeal. That and with the price of the head and all the fab needed, it might just be easier to just put an S38 in my car. I should be able to just take a M30 intake flange and weld it to the S38 intake.

Or I could just build a high-flow sheet metal intake.....:)

[mbonanni]

do bolth m50 and m30 swaps get roughly the same gas mileage?

the m30 is a 3.5l and the m50 a 2.5l, soo the m50 gets better right?

I would really like to do an m30 swap, but if the m50 gets better mpg, then thats what i will have to go for. It will be in a DD

[e46s54dr]

Just save your money to boost it... itll be your best bang for buck in the long haul.:D

[e46s54dr]

do bolth m50 and m30 swaps get roughly the same gas mileage?

the m30 is a 3.5l and the m50 a 2.5l, soo the m50 gets better right?

I would really like to do an m30 swap, but if the m50 gets better mpg, then thats what i will have to go for. It will be in a DD

M30s do use a little bit more fuel but it probably wouldnt be too bad. Id sacrifice a little fuel savings for the added power any day of the week.

[85e325]

My major problem not just with BMW's, but with all of the euro and jap engines, is that I grew up building old cast iron american v8's were you can see noticable power gains just by making simple changes in air and exhaust flow either by port and polishing the heads and intake, or installing long tube headers with a 3 inch exhaust. Where as "modern" engines are built with a lot tighter tollerances and are already reativly close to the max NA power levels.

I would really like to build a motor using the "old world" methods. I love turbos but the way I see it, It's just one more thing to break. By just building a massaged over NA engine, I still get "some" HP gains with having to worry about a turbo failing.

[85e325]

M30s do use a little bit more fuel but it probably wouldnt be too bad. Id sacrifice a little fuel savings for the added power any day of the week.

Another thing to consider, is that last time I checked the M50 requires at least 91 octane, where as the M30 takes regular. The difference in gas prices alone would be worth the loss of fuel mileage

[Brezzi]

My major problem not just with BMW's, but with all of the euro and jap engines, is that I grew up building old cast iron american v8's were you can see noticable power gains just by making simple changes in air and exhaust flow either by port and polishing the heads and intake, or installing long tube headers with a 3 inch exhaust. Where as "modern" engines are built with a lot tighter tollerances and are already reativly close to the max NA power levels.

I would really like to build a motor using the "old world" methods. I love turbos but the way I see it, It's just one more thing to break. By just building a massaged over NA engine, I still get "some" HP gains with having to worry about a turbo failing.

guys have put 5.0s in e30 before maybe you should look into that I've heard those engines are cheap as well. If your used to american engine modding and aren't a purist It could be a good fit.

[85e325]

I have thought of that, but I would like to try to keep it all in the BMW family