M30 vs M90 or combination of both?

[ericgoum]

Hello all,

This is my first post here, but I have been following this forum and in particular the M30 swap forum for some time now. I've learned a lot about what is involved with the M30 swap, but I have a few questions.

Here is what I have:

-M30 B34 with the B35 oil pan/pump w/ necessary wiring/ecu
-Lots of e28 parts from my 535i that was totaled
-A complete Euro 635csi parts car with highlights being M90, dogleg transmission and I think 3.07 LSD

Here are my goals:

-Initially I want to have a daily driver NA setup with stock ECU that I can take to autocross every now and then.
-Eventually I want to megasquirt this engine.
-Finally I would like to turbo this motor using megasquirt to give me somewhere in the 350hp range.

Here are my questions:

1. Should I use the M30 or the M90 for this? It seems like from what I've read the M90 would make the better NA car if that was my only goal. Does anyone have experience adding a turbo to this motor? I should mention that the person I bought the 635csi from mentioned it had a cam upgrade, although I'm not sure which degree it is, the receipts only mentioned schrick cams.

2. I plan on rebuilding which ever motor makes sense. Price is a concern with me, I really have no clue how much more it would cost to do the M90 over M30. More than likely I would stick to basics like rings/bearings for bottom end and whatever might be need for head. Is the M90 harder to find the necessary parts to rebuild on a reasonable budget?

3. With the 2 motors I have is there some kind of mix matching I can do between them? I ask because I saw a few old threads about using the M90 to do a stroker motor and it interested me. Once again I don't have a budget that would allow for much else in the internal parts other than what is necessary for a basic rebuild.

4. Finally, as much as I'd love to keep the close ratio dogleg transmission for this car, it just doesn't make sense considering I will be doing some degree of daily driving with it and I could not stand the 1:1 5th gear at highway speeds. Which transmission would be a better choice the one from a e28 or e34.

Thanks for reading my long winded post. Of the BMW forums I frequent this one seems to have the most knowledgeable members in regards to this swap. I hope posting here will help me find the answers to my questions. I'm sure this won't be the last time I have a bunch of questions like this.

Thanks in advance,

Eric

[Good & Tight]

The M90 is really not a stroker motor, it has a 84mm crank compared to the 86mm M30.

The heads are interchangeable, so it would make sense to put the M90 head that has the cam onto the B34. I have this same combo and it works very good.

Plus if you plan on going turbo the M30B34 compression is 8.5 compared to the 9.1 M90.
You can run pump gas easily without fear of detonation when turbo.

For the tranny I would get the 265 the one with the removable bell housing.

[ericgoum]

With the heads being interchangeable does that mean that both have the same head gasket? If not which would I use? Are there any special parts that I need to swap the heads or can I literally put the M90 head right on the b34 block and call it a day?

Will having a higher duration cam have many negative effects in terms of blow by and scavenging losses once I put a turbo on the motor? I thought that you typically want less overlap when you start boosting a motor. Does anyone have experiance boosting an M90 or motor with high duration cams?

The 265 transmission comes out of the e34 correct?

Thanks again.

Eric

[Good & Tight]

With the heads being interchangeable does that mean that both have the same head gasket? If not which would I use? Are there any special parts that I need to swap the heads or can I literally put the M90 head right on the b34 block and call it a day?

Will having a higher duration cam have many negative effects in terms of blow by and scavenging losses once I put a turbo on the motor? I thought that you typically want less overlap when you start boosting a motor. Does anyone have experiance boosting an M90 or motor with high duration cams?

The 265 transmission comes out of the e34 correct?

Thanks again.

Eric

Same headgasket, you could also use one from an S38 engine.

I'm running a schrick 284/280 on my boosted engine with no issues.

[wildstoats]

The 265 transmission comes out of the e34 correct?

Some e28s also had 265's. Just FYI.

[rhett325i]

I thought the 265 came from an E30 M3

[Lurker27]

My E34 M30B35 came with a G260...I believe they all did

[ericgoum]

Ok, so the 265 came out of the e28. I tend to get it mixed up with the 260 because of the model numbers...doesn't seem like a natural transition to me. Anyways, now that I have that figured out. Were the differentials in e24's medium case like the e28's or were they different? Just trying to figure out what I can keep from the 635csi and what I need to acquire.

Thanks.

[Jean]

The 265 transmission comes out of the e34 correct?

No, 260/6 is used in e34s with m30.

[wildstoats]

Ok, so the 265 came out of the e28. I tend to get it mixed up with the 260 because of the model numbers...doesn't seem like a natural transition to me. Anyways, now that I have that figured out. Were the differentials in e24's medium case like the e28's or were they different? Just trying to figure out what I can keep from the 635csi and what I need to acquire.

Thanks.

Well not all e28's had g265's just for the record. There is a breakdown on what transmissions came in what cars but I've been searching and searching and can't seem to find it. I will post it up if I come across it again.

As far as diff's go e24 and e28's are the same. All medium case except for the ///M cars which had large case diffs. Obviously you will need to use the back plate from an e30 to make a e24 diff fit on your e30.

[wildstoats]

Ok, found all the info, this should answer most of the transmission related questions:

http://www.m30swap.com/index.php?title=Transmission

[ericgoum]

Thanks for finding that information. Seems to be a pretty interesting site.

Good & Tight: Did you ever run stock ECU with the Schrick cams or were you running megasquirt at that point? I'm wondering if I need to just get all the parts for running megasquirt at this point as well.

[Good & Tight]

Thanks for finding that information. Seems to be a pretty interesting site.

Good & Tight: Did you ever run stock ECU with the Schrick cams or were you running megasquirt at that point? I'm wondering if I need to just get all the parts for running megasquirt at this point as well.

Never ran the stock ECU, went straight to MS.

The link for the transmission's has great info. I just checked the extra tranny that came from my M90 and the first 3 casting #'s are 262, if the site is correct I have the dogleg tranny!!!
woot woot!!!!

[wildstoats]

The link for the transmission's has great info. I just checked the extra tranny that came from my M90 and the first 3 casting #'s are 262, if the site is correct I have the dogleg tranny!!!
woot woot!!!!

Are you sure it's not just a 4-speed g262? That was the stock transmission for the e12 (assuming that's where the M90 came from). I guess the easiest way to tell would be to check the shift pattern. Found this golden nugget floating around mye28:

Getrag 262 is the 4 speed from E12 era. A very good 4 speed, but only 4. However, sometimes the highly regarded 265 is called a 262 since the front casting has 262 cast into it. And the 265 is a 5 speed. Confused yet? No? Then I'll keep going. There are two different 265's, but one is very rare and a close ratio "dogleg" which only came in Euro cars. The common OD 265 has 5th up and to the right of 4th. The close ratio has 5th straight back from 4th. Both have a 3 piece case, not including the removable bellhousing.

The OD one, which is by far more common in the US, it will have 4 side to side shift gates, the close ratio dogleg will only have 3, or maybe 3 with an offset. And the OD has 4 to the front, which translates to the back if the linkage and shift support aren't attached. The close ratio dogleg has 4th and 5th straight up and down form each other.

[ericgoum]

Here is some interesting info in regards to the different transmissions and ratios that I found:

http://metricmechanic.com/catalog/bmw-6-cylinder-transmissions-and-gear-charts.php

If all I was going to use this car for was autocross or track I would definitely keep the dogleg transmission. It might take a while to get used to 1st being down and to the left.