Let the machinist port & polish the m30 head?

[George M]

Same here Marc...welcome to the board! No question you will add a measure of technical insight. Glad you have joined the group.
Cheers,
George

[Bill R.]

gain but i would take it with a grain of salt unless he has a flow bench there and a dyno and has done many of them on the bmw m30 specifically...Without a flow bench its virtually impossible to tell what you're doing , whether helping or hindering.... and if done correctly you can gain flow without losing velocity in the port so peak torque rpm is not changed, it may even be helped or lowered more, there are many variables to a good port job on a head and the valve grind is an important part of it, such as what width is he cutting the seat to, and where is he placing the seating surface on the valve, is he sinking the exhaust valve any? Is he using a radius seat? Is he cutting away the valve guides in the port or shaping them for flow? My brother has done alot of port work on a few different head designs and he has literally thousands of hours in each.... Of course once you find out what works best for a particular head then its not as bad to duplicate it as long as you keep your templace head around...
So what i am getting at is that unless he ports a large number of bmw heads and has the test facilities to verify what his changes are doing I would hesitate to pay anybody for a ported head...

I dropped off the head, timing cover, & regrind 284 today. The machinist, Phil, recommended by Craig, was knowledgeable & very positive. He said the reground cam looked very good. He also assured me that the head would be returned at tdc, as dropped off.

He pointed to some areas around cylinder #6, indicating I had beaten a potential gasket problem. There were radial marks, from the combustion chamber in the aluminum head.

Phil mentioned that he could port & polish the head for some 15 additional horsepower. This was a guesstimate & would add a week to the downtime. I'll probably defer this in an effort to maintain the torque off idle.

Thanks for the recommendation Craig.

[Craig]

This guy does do a lot of BMW work. It's not all he does, but I've been in there twice and he had a couple of them sitting around each time.

I don't know enough about these engines to say whether 15hp is realistic or not though. I'll be anxious to see your new dyno numbers with the cam in place.

[1992 BMW 535i]

I agree, but even with a flow bench, I doubt that anyone could improve the flow enough to generate that high an HP number without significant collateral improvements. Matching the Intake manifold, head and headers could theoretically bring 15HP. I've looked at my head and it's beautiful. Wouldn't want to remove too much material and disturb the turbulence flow necessary to create good fuel atomization...

[1992 BMW 535i]

Please post the results once you get them, I'd be interested to see them!

[Hector]

your cold air intake? Just curious.

Please post the results once you get them, I'd be interested to see them!

[1992 BMW 535i]

Contrary to popular opinion, I saw an improvement right off of the bat. I made a very old-school, low tech test to check throughput on the stock set-up. I connected the whole thing to a vacuum cleaner and checked how hard the unit had to work to get air through. Then I did the same thing with my K & N set-up and saw a huge difference in the effort being exerted by the old Hoover.

It also made enough of a difference to feel "by the seat of my pants" and I've noticed improved gas mileage as well.

[Hector]

One cool thing to do would be to stick a thermocouple inside the cone (assuming you have this setup) with and without the heat shield to see what delta T you'd get. Don't know if you have a heat shield but always wondered how much of a T difference this makes. The increased air flow plus the lower T air sucked in should give the most bang for the buck.

[Martin in Bellevue]

[mikey535im]

Wouldn't want to remove too much material and disturb the turbulence flow necessary to create good fuel atomization...

This is the reason I feel that 'polishing' is a waste of time , money and possibly efficiency. Unless of course your feeding 600+ HP , the rough intake port promotes fuel atomization. Correct me if I'm wrong.
Mike