connecting rods for m30 rebuild

daicos35

daicos35

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Guys,
does anyone have a good source/reccomendation for aftermarket or second hand original, 144 mm con rods, as used in the M class engines based on the m30 style block,
Thx Mike
 
Why would you want to use aftermarket / other rods? The stock rods are already very balanced and pretty light, for what they are. They are also very strong, and have been shown to take more than 20psi (of boost) easily.

That said, you can still get rods from BMW, last I checked, and there are several good aftermerket suppliers, lik Pauter and Eagle. Usually run about 1000$ US for a set of 6.
 
Hm, well, based on the realoem part specs, the M30 used the same con rod during the entire run. The S38 and M88 used different rods, and were only used in those engines. Give how close the blocks are, I would bet money you could use M30 rods with custom pistons, which would also let you do your own custom compression ratio.

I'm afraid you are looking for a rather rare item, since the rods are usually very sturdy and have a very low demand.

What do you want the rods for? If you spill the beans on the whole project, the board may be able to help you find what you are looking for in a more or less complete package.
 
Am building an engine for my E9, that is period correct in terms of technology and simplicity (read alpina style), for performance street use.

I have an m30 b35 engine (91 535i), along with an 88.4 crank.
I will bore to 94.6, giving 3730 cc. Am having custom JE Forged pistons made, to run the engine at 10:1, along with a schrick 284 cam (mild , not hot, to preserve idle), dual valve springs etc.
I plan on running mallory mechanical advance distributor, and triple sidedraft 45mm dcoe9 carbs.
I dont need more than 270 ish hp, and am debating whether the last piece of the puzzle could ne longer con rods (so looking at cost/benefit).
Thx mike
 
If you are getting custom pistons, why are you trying to get custom con rods? The pistons can be sized to use the proper rods. Refresh my memory, an 88 crank is from the B35, not the S38B38, right? If so, then to keep everything peachy, you should use the stock size rods, as increasing the rod length would make the pistons hit the head.
 
The 88.4 stroke comes from the 3.3L E3 from 73-74 ish, so I can stick with the 135 mm rod, and have pistons made to suit , or I can get a 144 mm rod and have pistons made that are even lighter , because they have less material in them, given the piston deck height is lower.
The m88 had 84 stroke, 93.4 bore and 144 mm rod, the b38s36, had an 86 stroke, 93.4 bore, and 144 mm rod, the b38s38 had 90 stroke, 94.6 bore and 142.5 rod, in other words , all of the M engines used as long a rod as possible.
 
Ah, I see. I remember trying to find one of those cranks a while ago but had a bit of trouble with it.

The build you described sounds quite nice. Are you planning on any head work, like even bigger valves, a P&P, etc.?

The lighter pistons can be nice, but if you combine it with a lightweight flywheel, it may be somewhat tiring to drive, as the revs will drop off too fast.

You may be able to find a set of S38 rods from BavEngine, as they seem to get quite a few tired S38s, which usually get broken down rather than rebuilt. Some people have had poor experiences with those guys, however, so watch out. In terms of other providers, I'm not too sure where you would go, as just about anybody else with a working or even tired S38 tries to either fix it or sell it as a complete package. If I remember right, the S14 is based on the S38, so you may be able to use S14 rods, which are a bit easier to come by, but not by much.
 
Thanks for the advise re bav engines, I will try them.
Re the engine, it will get a port and polish etc, that late head already had bigger valves and flowed very well, so i wont do any more than the cam, springs, maybe rockers, and the p@p,
thx again, Mike
 
Am building an engine for my E9, that is period correct in terms of technology and simplicity (read alpina style), for performance street use.

I have an m30 b35 engine (91 535i), along with an 88.4 crank.
I will bore to 94.6, giving 3730 cc. Am having custom JE Forged pistons made, to run the engine at 10:1, along with a schrick 284 cam (mild , not hot, to preserve idle), dual valve springs etc.
I plan on running mallory mechanical advance distributor, and triple sidedraft 45mm dcoe9 carbs.
I dont need more than 270 ish hp, and am debating whether the last piece of the puzzle could ne longer con rods (so looking at cost/benefit).
Thx mike
Click to expand...

I built a similar sort of engine for my 2002 touring (S14 crank, JE pistons, 304 cam, Alpina A4 injections). I went with stock rods because it is a street car and S14 or Pueter or whatever rods cost a lot of money and the value only really comes in after ~7500 rpm. As a street car, the engine is rarely going to see that -- and certainly not for long periods on end, like a race car.

If yours is street use, as you say, I wouldn't bother with anything other than stock rods unless you plan to live at the redline. My MSD is chipped at 7.5k and the stock rods work dandy, and saved moeny for other performance items that really help, like an alumium flywheel. Now, that is money well-spent, IMHO. I think these are all questions of where the money is best spent, unless, of course, if you have an unlimited budget.....

[Next year, the coupe will get it's engine work done, just the top end, though probably -- triple webers and an Alpina airbox, 288* cam and p&p. If I was doing the bottom I would do basically what you are, stroker crank and J&E pistons, not much else: good, strong, simple, low maintance POWER]
 
daicos35 said:
Am building an engine for my E9, that is period correct in terms of technology and simplicity (read alpina style), for performance street use.

I have an m30 b35 engine (91 535i), along with an 88.4 crank.
I will bore to 94.6, giving 3730 cc. Am having custom JE Forged pistons made, to run the engine at 10:1, along with a schrick 284 cam (mild , not hot, to preserve idle), dual valve springs etc.
I plan on running mallory mechanical advance distributor, and triple sidedraft 45mm dcoe9 carbs.
I dont need more than 270 ish hp, and am debating whether the last piece of the puzzle could ne longer con rods (so looking at cost/benefit).
Thx mike
Click to expand...

As has all ready been stated if this is a street engine the cost/benefit ratio of having custom rods built is something only you can decide it's your money after all.
I'm no engine building expert but as I understand fitting longer rods has the effect of flattening the torque curve and allowing the engine to rev more freely.
There is a guy on here in the UK who built a group 2 spec engine using custom rods and pistons and a 300 ish degree cam running mapable injection through throttle bodies and got 311 bhp at 7000 rpm so I would imagine that your goal of 270 bhp with a larger capacity should be easily attained, let us know how you get on.
 
Ireland eng. has them

Jeff Ireland carries them for $145 each, in Duarte, CA (LA area). They are aftermarket HD with 7/16 bolts. Website - iemotorsport.com
 
Another advantage of the longer rods will be a lower rod angle, which will contribute to the longevity of the bottom end.

That said, M30 bottom ends tend to last just short of forever anyway...
 
Rods

look to hear about the progress did the same type of set up. Used a euro 635 block and a U.S crank. You can go bigger piston longer rod. So displacement and stroke is better. Which means more H.P and more torque.... Call Ireland Enginneering Wish you all the best in the build
 
Thx to all for the advice.
I went with std length con rods. Engine is built and in the car, it is running, but has gone straight to a weber dyno tuner, who will set them up for me, along with the mechanical advance mallory. I have posted currents pics under the cs folder on the website (diacos35's cs, will be on once approved by our host), will post final engine bay shot, and dyno outcome in the next few weeks once I am on the road.
 
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