Let the machinist port & polish the m30 head?

[Martin in Bellevue]

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.

[JoeS]

I'll probably defer this in an effort to maintain the torque off idle.???

Why would you do this, when you have the adjustable cam gear to recoup the torque issue?

[1992 BMW 535i]

Honestly, I think that 15HP is a little high. I've seen 10HP gains on old American made heads which were nowhere near as good as a BMW unit. Extrude-honing the heads may give you an additional 5-7 but 15? No way.

[George M]

again agree with 92 BMW 535i...wish I knew your name :-)...also believe 15 hp is high...5-10hp is probably more accurate. Returning the head TDC on no.1 doesn't matter as you should Martin check all the valve clearances before you install the head and perhaps just before you fire the motor. I wrote some time ago about valve clearances changing slightly due to torquing the head...they do...so a lesson there to pass along to you. Where did you get the regrind spec's from?...were the intake lobe's the only side of the cam that was ground?
George

[Martin in Bellevue]

I gotta get the cam close to TDC before attaching timing chain; that's a big concern. What I don't want to do, is have to move the cam around much with the head off the block. For me, it is alot easier to turn the crank around, holding the chain up & looking down on the tdc mark, especially with everything out of the way. At tdc, pistons 1 & 6 are up, & the valves better be closed. I'll be checking valves gaps a few times, thanks for the reminder.

Don't really have any of specs on the ireland 284. Jeremiah said everything but, that it was a ripoff of a Schrick. The exhaust lobe backsides looked to be relieved as well as the intake lobes. I have no cam card to go by. We'll see if it is junk, & whether I can put things back together with love.

I spent a few hours with a rag & some gasoline hand rubbing the piston tops. I rotated the crank a few times, bringing 2 pistons up at a time, for the cleaning. That is not a good time, but I'm glad it happened. I shot some oil towards the rings & tried to keep things up & clean. I also spent a pack of wooden q-tips cleaning head bolt threads in the block.

[632 Regal]

port and polish huh?
is this guy a specialist in BMW heads or just in general has ported heads before? I can port heads, dont think i would want to port mine without knowing exactly what would effect what, probably end up with less power all throught the band but you would never know unless you dyno the engine with the new cam and then port the head and dyno it again. I dont think I would opt for that one personally.
Just my 2¢

[Hector]

Also, I looked into this a while back because thought I'd cash-in on the service since the head had been taken apart. I believe the local guy quoted me between $300 to $400 for the job--the gain in power did not outweigh the economics of the situation so couldn't justify pissing away the cash. I got the feeling this guy pumped up the price when he heard I had a bimmer head.

[BigD]

My engine builder wouldn't do it on my M5 because he said the ports are already gorgeous, would just be a waste of money. I asked him about pnp in general and he said if done right, it can have a slight impact on some motors. And that "right" includes porting the intake to match, otherwise if you just port the intake or just the head, you will actually lose power. I didn't ask for specifics, maybe George can explain that...my guess at the time was that the "step" would create uneven flow/stagnant mixture.

[George M]

sounds good Martin...rotating the cam back to no. TDC is pretty easy with the head off the engine...say on a bench for example. There is a large hex with the sprocket off that makes rotating the camshaft straight forward using a large crescent wrench on the hex..what I did and check clearances as I put the camshaft through 1 full revolution. By all means set it to no.1 TDC where both the intake and exhaust valves are closed for no. 1 chamber before you set the head back on the engine. Porting as mentioned by Jeff and BigD is a slippery slope and many times is not beneficial for some of the reasons stated...port agreement between intake and head....physical shape of the ports and a rough casted surface can many times create more and not less flow due to increased turbulence based on higher boundary layer shear force near the port surface...some of the reasons I didn't touch my stock ports. Bill has written pretty comprehensively about this previously if someone can dig it out of the archives.
Good Luck with your engine rebuild Martin. I sure enjoyed mine...the big six is a beautiful engine to work on.
George

[1992 BMW 535i]

Sorry George, the name's Marc, nice to meet you! :)

[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]

http://www.bimmer.info/bmw/Martin5er/crown.jpg

http://www.bimmer.info/bmw/Martin5er/pistons.jpg

http://www.bimmer.info/bmw/Martin5er/profile.jpg

[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

[Jeff N.]

Couldn't quite remember when we talked on the phone this AM but they are the same....

[Jeff N.]

Here's a comparison pic of the stock port vs. Metric Mechanics port job. CNC machined, Jim R. states it improves stock flow 13%. Rowe specializes in BMW headwork.

Note the smooth but not polished finished.

http://home.comcast.net/~jsnord/pics/sbs_ports.jpg

[1992 BMW 535i]

Very good idea, I'm going to give it a try. BTW I do have the heat shield and it looks great!

[632 Regal]

ill admit thats real purdy there! but again thats from a specialist that used a cad program to reach the desired results. That is a LOT different than some guy commin in and hitting it with a grinder, do you follow what I mean?

[632 Regal]

weird design of the tops, why bother with the little bit of domes, probably make more power without them.

[Jeff N.]

weird design of the tops, why bother with the little bit of domes, probably make more power without them.

I believe that's known as a "reverse ditch cut" and it's a reversion management technique.