Big Time Poster
milled head + euro motor = thicker head gasket?
I FINALLY got the head to the machine shop. I am getting things done at a snail's pace.
The machine shop took .01" off the bottom of the head. This equates to .254mm. Given that the pistons are the 10 to 1 compression ratio euro-style; would anyone recommend that I install the .3mm thicker head gasket? Or is it safe (interference-wise and/or compression-wise) to run the stock-thickness gasket?
I ran various searches on mye28 and .info. I read that many folks went up to .03" or even .04" milled and still ran the stock thickness without issue, but none of the results were in reference to the 10 to 1 piano-domed piston. Aside from that fact, my ECU is an early fixed-mapping with added O2 sensor; so would I run the risk of pinging with a stock gasket?
I do not care to spend the extra cash for the thicker gasket. I just want to be informed and ecourage discussion.
Major Contributor
1 thou is irrelevant,But you might want to remember that it shortens the Cam chain,or do you mean 1mm, whole different ball game.If you really want to keep CR the same then machine off the piston heads, get out a calculator to calculate the volume of metal required to take off.
Big Time Poster
definitely just .01 (one-hundredth) inches or .254 mm...
4 Grand Master
Stock gasket. No worry about chain, the tensioner can cope with .010
EDIT Bently says .012 is the limit for machining and BM recommends.3mm over gasket, who am I to argue. I think the concern is detonation not piston to valve "interferrence.
Last edited by Ross; 07-05-2007 at 05:57 PM.
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3 Grand Master
Apples and oranges
I would like someone to say that if you take ten thou off the head and use the standard gasket, then the pistons definitely wont hit the valves. I wontOriginally Posted by 31Hertz
Oct '00 E46 330i. Feb '92 525i (departed)
Big Time Poster
1/4 of 1mm doesn't seem like much, but yeah; I am hoping to hear something like that as well. My gut tells me it won't, but my gut is also the place that makes poop...I would like someone to say that if you take ten thou off the head and use the standard gasket, then the pistons definitely wont hit the valves. I wont
It will shorten the chain which means slightly retarded cam timing. I am not so worried about that. Or will this actually work in my favor to avoid detonation?
The compression ratio will be around 10.25 to 1 according to reliable sources.
Apocalypse or Sunshine?
Last edited by 31Hertz; 07-06-2007 at 06:43 AM.
3 Grand Master
Not familiar with your motor but if you shorten the distance between the top and bottom sprockets, surely the chain is longer?
Oct '00 E46 330i. Feb '92 525i (departed)
Big, Big Time Poster
Not familiar with your motor but if you shorten the distance between the top and bottom sprockets, surely the chain is longer?
Was wondering the same thing, you beat me to it
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5-10 Grand Master
The stock HG thickness is 0.070" and you took off 0.010"... You should run a 0.080 gasket and yes, 0.010" does make a difference! That would probably raise compression from 9.0 to 9.5
Big Time Poster
The chain will slacken more, but the tensioner will take care of that. HOWEVER when the cam sprocket and crankshaft are lined up to TDC there will be ever-so-slightly more slack on the guide rail side of the chain. Of course when the motor starts this slack will go to the tensioner side; which means the cam will be slightly behind where it would normally be in the stock setup.Not familiar with your motor but if you shorten the distance between the top and bottom sprockets, surely the chain is longer?
I am still riding the fence on this one...
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