mill m20 heads

[sl0ride]

I have an extra M20 head,. Anyone have any info on how much i can mill off them to bump up the Cr without fuckin up the heads?

[SpecM]

not much... maybe .010" tops?

[XvillainousX]

Did you ever mill your head? If so, by how much? In my youth I milled my integra head 0.060 and enjoyed it. I'm also curious as to how far we can mill the M20 heads before the valve hit the pistons.

[moatilliatta]

I think its .027 maybe....

[Knockenwelle]

There are three cast-in "dots" in the deck surface, about 5mm diameter. Those are the service limit indicators, so don't go past those. It's hard to state a number, cause you rarely know the whole history of a head. As far as P-V, you'll just have to measure it. Running a stock i cam shouldn't be a problem at the maximum cut depth. I found that with mine decked to within .004" of the dots, my cam timing changed about 3 deg, so keep that in mind. However, running the big Schrick, the compression bump is a welcome addition.

[StereoInstaller1]

I have heard there is someone out there making an adjustable cam sprocket

[nando]

I have heard there is someone out there making an adjustable cam sprocket

there are 3 that I know of, they cost between $150-$200.

[StereoInstaller1]

there are 3 that I know of, they cost between $150-$200.

Any links?

[akorcovelos]

I know I have seen one guy on ebay selling them.

[eugeman]

My understanding is 0.1mm shaved = 0.1:1 increase in compression as a general rule of thumb on the M20. You would really have to measure the total volume to get an accurate final of how much your compression has increased after shaving. I believe the max amount one can shave on an unmolested cyl head is 0.4mm before it becomes scrap metal. But again you would have to measure the height of your existing cyl head material before shaving, to see how much farther you could go.

I bought one of these, and my initial impression is that is of decent quality though I have yet to install it:

http://cgi.ebay.ca/BMW-Adjustable-Cam-Gear-E21-E28-E30-E34-Z1-M20-Engine_W0QQitemZ330288129916QQcmdZViewItemQQptZMotors_Car_Truck_Parts_Accessories?hash=item330288129916&_trksid=p3286.c0.m14&_trkparms=72%3A1215|66%3A2|65%3A12|39%3A1|240%3A1318

[Kingb]

How much was that in Dollars? i am about to have my head milled due to overheating and a blown HG. So shouls I get it milled a little more than just to level it out.
Do you have to do anything else like run highre octane gas or anything??

[nando]

My understanding is 0.1mm shaved = 0.1:1 increase in compression as a general rule of thumb on the M20. You would really have to measure the total volume to get an accurate final of how much your compression has increased after shaving. I believe the max amount one can shave on an unmolested cyl head is 0.4mm before it becomes scrap metal. But again you would have to measure the height of your existing cyl head material before shaving, to see how much farther you could go.

I bought one of these, and my initial impression is that is of decent quality though I have yet to install it:

http://cgi.ebay.ca/BMW-Adjustable-Ca...3A1|240%3A1318

overpriced junk, that's merely a stock cam gear that's been cut up and a plate bolted to it. You can get one CNC machined from PPF for about the same price or maybe even less. I don't have a link but there is a thread on E30tech in the engine management section that does, it's called something like "cam sensor options for the M20".

[Kingb]

Any links?

Just saw this on Ireland and is cheaper than the one on ebay

http://store.nexternal.com/shared/StoreFront/default.asp?CS=ireland&StoreType=BtoC&Count1=412410914&Count2=329551339&CategoryID=3&Target=products.asp

[eugeman]

Just saw this on Ireland and is cheaper than the one on ebay
http://store.nexternal.com/shared/St...t=products.asp

Wow, that looks like the exact same piece of overpriced junk as the one that I've got. I'm glad I only paid $130cdn for mine. ;)

[nando]

Wow, that looks like the exact same piece of overpriced junk as the one that I've got. I'm glad I only paid $130cdn for mine. ;)

hey, I almost bought one for $60. But I'm not sure how much I'd trust the thin webbed part of the OEM gear at 7200rpm, after it has been cut in half, drilled/tapped with screws threaded into it and only 1-2mm of material left on each side. it may have been worth the price at $50-60, but definitely not over $100.