What's the best 3.5L block + head combo?

yellowbullet

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I've heard of people swapping different cylinder heads onto 3.5L blocks (not sure if it's the euro 3.5L or m30b35) to increase the air flow (more HP) and also cure overheating issues. Can someone explain this to me?

Also, what diameter piping headers is best for a basically stock 3.5L w/ a sport cam? 1 3/8"?

Thanks in advance.
 

velocewest

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All M30 heads have the same intake/exhaust ports, valves and combustion chambers until about 1988, when the M30B35 variant arrived in the e34 535i and e32 735i. When I say "all", I mean "all from the factory", so don't be taking me down the "No, Alpina did this and Hartge did that.." road. 8)

The M30B35 head has bigger combustion chambers, 1mm bigger intake valves and improved port shape that is assumed to improve the breathing of the engine. IIRC, BMW never really said one way or the other, but enthusiasts have promoted this theory. I don't know of anyone who has flow-bench compared the older and newer heads, but Todd at TCD was talking about it.

If you put the M30B35 head on any other M30, you'll lower the compression. If you put the head from an earlier engine on an M30B35 block, you raise compression but lose the better flow of the newer head. The M30B35 has the highest stock HP of any M30 officially imported to the US, so if you're looking for the most M30 bang for your buck without modifying or sourcing a Euro engine, that's it. I've been told you can install the larger intake valves in an earlier head without replacing the seats, you just need to have the seats and valves ground to match. That and a little judicious porting would give you higher compression on an M30B35 block with less flow loss. I think Alpina and Hartge upped both the intake and exhaust valves by 1mm or 2mm.

The overheating issue is not an overheating issue with the head, it's that early (roughly pre-1982) heads had large water ports with thin walls that would crack if the engine was overheated. The head itself did not contribute to the overheating, it just didn't take to it with any enthusiasm. This was mostly resolved in late 1981 when the water ports were redesigned. Any head with a 1982 or later casting date should have the better port design. Later model heads will still crack if overheated; I've got a cracked 1985 head in my garage that I'm using to bench-fit my intake and exhaust for a turbo project.
 

yellowbullet

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Tony, thanks for the detailed information! I ask this because I have in my garage a 1979 3.5L Euro engine, a 1986 3.3L engine, and about 5-6 cylinder heads lying around. Since I have more parts than I need, I thought about what I read on mixing and matching the block and heads into getting more HP.

I guess the best way is to keep the full Euro engine and just swap in the bigger valves - this way I won't lose compression AND have more flow.

On a side note, do you know what kind of aftermarket cams the Euro head takes? Same as the M30?

Thanks
 

x_atlas0

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Wouldn't the 3.5 Euro motor be a M90, rather than M30? If so, then you can get some additional displacement pretty easily.
 

yellowbullet

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x_atlas0 said:
Wouldn't the 3.5 Euro motor be a M90, rather than M30? If so, then you can get some additional displacement pretty easily.

Yes, it is the M90, but it seems very few people understand what "M90" means. What do you mean by I can get some additional displacement?
 

ScottAndrews

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There are two blocks and three heads.
I am not sure if Velocewest got the head thing exactly right.

The early Euro block, known as "the L block" due to the large white "L" painted on the side, is a derivative of the M49 racing motor. This motor has a 93.4 mm bore and an 84 mm stroke, and is essentailly the same platform as the M6, but without the 4 valve/cyl DOHC head. The displacement is 3453 cc and compression ratio is 9.8:1. This engine makes 218 bhp stock, and has a huge flat torque curve that will peel the rubber right off your tires; peak torque is 228 ft-lb, and I swear it must be from 2000 to redline. THi sengine has a lot of problems with pump gas (I mix my own gas with 91 octane and 30% toluene).

The later 3.5 liter engine was derived from the 3210 cc M30 (used in the 633 model). In its "3.3" liter from it had a bore of 89 mm and a stroke of 86 mm. Cr is 8.4:1. This unit made 177 bhp and 196 ft-lb torque.

To make 3.5 liters M30 was bored out to 92 mm. This unit made 182 bhp and 214 ft-lb of torque. The compression ratio is 8.0:1. Thie low poer was a result of the low compression ratio, an attempt to meet US smog regs.

In 1988, BMW made a modified head for the M30. This unit had higher compression and the power went from 182 to about 208. I believe this is where Velocewest is wrong. The later head was HIGHER compression, not lower. This was possible using pump gas because of the more sophisticated second generation Motronic engine management system.

If I had a choice of powertrains for an E9, I would use an M90 L-Block, a getrag 265 standard ratio trans and a 3.07 diff. Yeah, thos eare lanky gears, but the M90 has the moxie to pull it off. My 635 uses this setup and it is pretty quick. In a lighter E9 it would be killer. A good alternative for the acceleration minded might be to use a Getrag CR trans with this same engine and diff.

S
 

yellowbullet

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Scott,

I thought the L-Block had a compression ratio of 9.3:1? What problems did you have with pump gas? Do I have to mix my own gas as well? Here in Canada we have 94 octane if that makes any difference...

I also have 2 265s sitting in the garage waiting to be used, but I was thinking of going with a 3.25LSD. Would that be a bad choice? I'm new to the whole "5-speed gearing" scene, so I'll take your word for it. Do the CS's use 168mm or 188m differentials?
 

velocewest

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I skipped the Euro variants as I didn't know YB had a Euro engine. I also didn't talk about the 4 valve head because it's not an option on an M30 block. The later head used on the M30B35 has a larger combustion chamber. BMW only and always set the compression ratio in the M30 with piston shape. On the M30B35 engine, the pistons create a higher compression ratio even with the larger combustion chamber of the head. Putting this head on any earlier M30 will result in a lower than original compression ratio. It's a popular combo for turbo engines -- M30B34 block with M30B35 head.

My point about the earlier head going on an M30B35 block is you will bump the compression even higher with the small chamber head. My e12 has a 3.5 with 10:1 compression, a Schrick 282 cam, and first generation Motronic with a chip. I run pump premium with no problems at all. I'm surprised you're having trouble, is your timing maybe a bit too advanced?

Strictly my opinion, but I'd not put a 3:07 with anything other than a CR tranny. More personal opinion -- I'd never use a CR tranny. The 265 OD with a 3:64 or 3:45 gives much better acceleration with reasonable highway RPM's. The 3.07 just gives up too much acceleration for me. My POV is, the M30 has loads of torque, why not use that vs. shifting all the time? I have a friend with an e12 M535i -- M90, CR and 3:07. He's driven my e12, which has the above mentioned engine, a 265 OD and 3:64 final drive. He's driven my car and chased it, and will vouch it is quicker.

YB, the sideloader diffs used by the e9, e3, e12 and early e24 are all the same size. The later rear-load diffs shared by e28, later e24 and e30 have different sizes but are not directly compatible with the e9 subframe.

I believe what x_atlas0 means by "additional displacement...easily" is you could put an S38 crank in your M90 block and increase the stroke. The "easily" part might be debatable, as I think this takes custom pistons... :shock:
 

x_atlas0

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I was thinking more about using the crank from a 3.3L (the car, not the motor) in the M90, as it had a stroke of 88.4mm compared to the M90's original stroke of 84mm. It is true custom pistons would be required, but if he plans to upgrade the CR anyway, then pistons aren't such a bad idea.

Oh, and with any diff swap, don't forget that the spedo will have to be redone to account for the new ratio. The spedo gets the signal from the trans, rather than the diff like newer BMWs, thusly the spedo does the calculations to account for the final drive. I found a place or two in the southeast that would do this for about 300$. As was said earlier, the CS uses a side-loader, more specifically the big side-loader (The 2002 and the E21 used the small side loader) which was also used in the E12 and early E24's based on the E12 chassis. Unfortunately, this means they are rather tricky to find, at least in LSD form, especially in the ratio that requires no spedo change. (3.45) Supposedly, one can replace the entire rear subframe and suports with those from an E28, allowing the coupe to use the newer style (and more abundant) diffs, but I haven't tried it, and hence, cannot confim it.

Right now, I have the 265 with the stock 11:38 (3.45) rear end, along with the motor / Motronic combo I have in my sig. One can patch out in 1st pretty easily, 2nd is pretty difficult, but the car takes off suprisingly quickly in 3rd. If you hold 3rd from about 2-4k, you'll do 70 in about 5-6 seconds. The chassis is so sorted that you don't realize you are going that fast until you check the spedo. When I was merging onto I-75 on the way to the body shop, my dad'd Mini Cooper S (with all the Cooper Works stuff, so it's about 200hp) had a bit of trouble keeping up.
 

teahead

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Sowhat would putting a M30B35 head on a M90 would entail? Would that LOWER compression due to bigger combustion (CC) chambers?

Was consideirng that combo if the later head flows better? May increase HP, but lower torque?
 

Gazz

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Probably a well worn discussion - however.

I have heard about the M30 taken out to 3.8 ltrs, eg. Paul Cains 3.8 CSi and others. How is this done?
Is there a way using just the crank and rods from an M30B35 or do I have to start Frankensteining with cranks, rods, heads etc?

Using the maximum standard M30 bore and stroke block, i.e. 92mm X 86mm from an M30B35 I would have to bore the block to 96.8mm. This seems excessive if it's even possible, which I doubt. Boring to 93.4 ( '89 ~'92 M5 ) takes it to 3535cc, and 94.6 ( post '92 M5 ) takes it to 3627cc, still way short of 3.8ltrs.
Using a post '92 M5 90mm crank from an S38B38 would do it but now it's getting expensive given (a) the scarcity of M5 cranks in Australia and (b) the ready availability and cheapness of M30B35 complete engines here. And is the S38 crank able to be simply fitted to the M30 block anyway?

In the end is the extra size - 3.5 ltrs vs 3.8 ltrs really going to make that much difference given that I won't be driving it like I stole it?
Perhaps I should focus on building a really sweet running balanced 3.5 which would rev more responsively than the larger engine.
I suspect that in Paul Cain's case it was just as much an engineering exercise as it was a horsepower challenge.
 

TodB

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I've got a franken M30 motor in my E28 which consists of an '85 block, B35 pistons and a stroked crank which is the way it came from Dinan via the PO. After the headgasket went on me, Paul Burke sourced a B34 head, rebuilt it with 2MM larger valves and added one of his cams. I tuned via a Miller warchip and added a MAF, a bored out throttle body and headers. This config ran right by the 19 lb injectors at 4.5k revs so I went to 24s which work great.

End result is 235 HP and 265 lbs torque at the wheels run through a 3.64 LS. Goes right along, pulls like a train and its not too buzzy on the highway. Great motor, I'd love to have it in my coupe.

These projects have a way of getting out of control and this one was no exception...:oops: If I did it again, I'd get a stock B35 and throw a Paul Burke cam at it to get a 40 Hp and torque bump, stay in the Motronic family and get the same (or better) result. Cheap and easy.

Now if you turbocharge...

I'd like to see a real dyno sheet on the MM motors and not estimates or projections.
 
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Gary Knox

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Gazz, Markos, et al,

The company that built the engine in my car, Metric Mechanic, sold their upgrade package as a 4 liter HiFlo Sport engine. I can not verify that it is 4 liters, and suspect it may be 3.8 liters. The engine was built and installed by them, along with the overdrive 5 speed trans and 530i fuel injection system, modified cam, etc. The build was completed in 1993, with the total bill to the ownerwas over $15K. The engine does have a lot of torque and power and runs smoothly.

Recently I went to their web site and found that their largest 'Sport engine' is now listed as 3.7 liters and 270 hp. Link: http://metricmechanic.com/wp-content/uploads/2015/09/Price-Book-9-22.pdf . As of 5 months ago when I bought the car, they were still listing 4 liter HiFlo Sport engines. WHO KNOWS!!
 
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