Gas Flow Head - is it worth doing?

Marc-M

Marc-M

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Over the next 2 months I will be sending my CSL engine off for a complete rebuild and could do with a little help about my options.

I am going to keep the engine as factory specification, but was contemplating getting the head gas flowed and putting a better more free-flowing exhaust manifold on.

But I guess the question is – will it make any significant difference in performance and its it worth spending the extra money doing it?

I will be keeping the original fuel injection and that would most probably have its own issues and could negate the head and exhaust modification.

Any feedback would be appreciated to help me make my mind up.

Marc
 
At the suggestion of SFDon I put a Schrick 284 cam in my stock head - big difference. As I recall reading the cost vs. performance of headers doesn't pay off as the stock manifold is pretty efficient.
 
Marc-M said:
Over the next 2 months I will be sending my CSL engine off for a complete rebuild and could do with a little help about my options.

I am going to keep the engine as factory specification, but was contemplating getting the head gas flowed and putting a better more free-flowing exhaust manifold on.

But I guess the question is – will it make any significant difference in performance and its it worth spending the extra money doing it?

I will be keeping the original fuel injection and that would most probably have its own issues and could negate the head and exhaust modification.

Any feedback would be appreciated to help me make my mind up.

Marc
Click to expand...
I would say a definite yes. Jaymic did mine several years ago. Big improvement IMO.
 
You said you want to keep the engine as factory spec. The precludes change in port shape, compression, cam, valve seat profile (eg 3-4-5 angle cuts). Because the engine is an air pump, I'd guess a really good porting job would provides some benefit. But this is where you should call someone who has built a 50 or a hundred performance M30's
 
Tremendous amount of guesswork to answer your question - even in the abstract. Porting is somewhat of a black art, mixed with a dash of science. Not unlike camshaft profiles, porting can enhance engine performance, but it often comes with trade offs. For example, some porting may promote better low speed torque versus high speed horsepower production.

The stock head port configuration is a relatively good starting point. There is always potential for improvement, generally at a price. The same can be said for the bottom end. Porting, polishing and balancing are all good things, in no particular order of importance. You did not specifically ask about changing camshafts. If this is something you are considering, it is not quite clear how the original djet FI would abide by such a change, without additional modifications. Returning to your original post, there are several things you might consider:

Do you have a budget?
What is your anticipated use of the car? Sit, show, go, go fast or go faster?
Who will perform the work?
Does that person, or the shop prospectively doing the work, have a track record? Can they point to realized performance gains? And what are the hard numbers and how were they derived?
How much for the service?
 
Here's a story about ported M30 heads that a guy named Paul Burke was doing. These were extreme M30 motors. Cost for head work was over $2000.
http://www.mye28.com/viewtopic.php?t=109539

There are many more stories about M30 motors on this site. Search and you will find.
In fact because of the E12 and E28 having variations of the M30 you will probably find more about the M30 motors on MyE28.com than anywhere else.
I've built quite a few engines and basically the most bang for the buck is higher compression and cams.
You could do a cam like Steve said with a stock motor and get some improvement but that will be limited by the compression. Higher compression makes more power.
There is a lot more science to this but won't go there.
Headers are sexy but on my M5 motor only provide about 10 more HP.
My suggestion would be to leave it stock like BMW built it. Certainly will make it more valuable in the end.
 
Paul's work was awesome. He built a custom head for me which included one of his cams and larger intake valves for my higher compression/stroked B34 motor. Others here have built motors with his pistons and cams with great results. I always enjoyed speaking with him. Unfortunately, he's all but all but disappeared from the BMW world taking customer money and deposits but not supplying the product they paid for. Its too bad.

I'd suggest staying stock also.
 
I wouldn't touch a correct year csl head.
Get an b34 head and port it.
 
You say you want to remain stock, but are considering changing the motor. Well it's your money and your motor, do what you like. But after some changes, will you/how will you modify Djet to take advantage of the changes? Presumably even a mildly built motor will benefit from a close look at A/F ratio through the operating range. I'm nobody's machine shopper, but what little I read here suggests that the physical changes to the engine may be easier than modifying Djet A/F ratio to accommodate or take advantage of such changes.

Comments anyone? Am I off my rickety rocker here?
 
Thanks for everyone input .
I think I will leave it just as it came out of the factory.
I was hoping that a mild gas flowing head and a better ex manifold was worth doing and some one would have said they had positive results - but that's what is great about forums, a wealth of info, and help.
So again thanks for the info.
It seams there are two many variables , and I do know once you start doing mods, other things start going wrong, or don't work in harmony.

I will just get the engine rebuilt and balanced.
Regards
Marc
 
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