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!