M30 head gasket thickness and squish height

[535ise]

Hi, does any one know how thick the M30 head gasket is when compressed with the head torqued down as i'm trying to reshape the squish area in my heads combustion chamber to match the Alpina B10 pistons/bottom end i want to use.

If i know how thick the H/G is it will help me to reshape the head.

I am also unsure of the proper squish height to use, after digging around on the net it looks like 0.040" or 1mm seems to be a fairly common sort of clearance but i'd like some feed back from some experianced members on here who are used to stripping/reworking engines please ?

This is the Alpina piston



This is what i've done so far to my head

[632 Regal]

basicly go with 1mm, use an old gasket to scribe a mark onto machinists blue around the chamber and blend it in, no sharpies except where the gasket contacts the head. you dont want to cut too much material cause you will drop compression. When your cutting the head do a little cutting at a time in ALL chambers, not one at a time so it will be more consistant. Measure with a burette and plexiglass when done to equal all the CC's out, you dont want any more than about 1 cc difference.

[535ise]

Cheers for the info Jeff

Measure with a burette and plexiglass when done to equal all the CC's out, you dont want any more than about 1 cc difference.

I've got some clear plastic and a syringe(sp?) ready for this but it's nice to know what the maximum differance should be between chambers.

I've just got to convert ML's to CC's now as the syringe i've got is in ML's.

All i've done so far is to smear some engineers blue marker stuf on the pistons, dummy fit the head with an old HG, turn the engine by hand then remove a little metal at the place indicated by the engineers blue and repeat this about 30 time's to do two chamber's(1 and 6) !

I've done just enough grinding to get the two cylinders/pistons past TDC, once i new what sort of shape i needed i've removed 80% of the metal from the other four chambers to speed things up. Next i will start the whole blue/dummy fit/grind process on the other four chamber's to bring them into line with the first two.

I'd like to find out the clamped thickness of the HG so i can substitute the HG for some thing else that will give me near to the right squish height if i carry on with the blue/dummy fit/grind process, if you get what i mean as i'm not brilliant at describing things.

To measure the clearance towards the end of the shaping/grinding i've bought some Plastigauge.

Thanks again for your help, i'll try to update this thread with some pictures and info as i progress

Andrew

[535ise]

1 Ml = 1 Cc

[632 Regal]

1 ml is 1 cc. plasigage? thats for bearings and crap not headwork. you can guess on the thickness of the gasket by micing a used or new one, they do not compress much at all, like .004 inch, its not rocket science. so your cutting the head cause what hits?

[535ise]

I thought i'd use plastigauge because the principle is sort of the same as it is on bearing clearances, you are measuring the gap between two parts that you can't get to do with feeler gauges etc. It comes in big enough sizes to match what i need.

Sorry, i've not heard of the term Micing before but i guess you mean measuring ?

Would the best place to measure the gasket thickness be on one of the metal cylinder compression rings ?

I'm using an Alpina B10 bottom end that has high C/R pistons that hit part of the head. On the stock M30 that part of the squish band is flat with the gasket face but the Aplina pistons angle upwards about 22 degrees in to the chamber.

[632 Regal]

okay i think im on to what your doing, maybe. the uncompressed gasket thickness is what you want to use as a measurement.

plastigage isnt what you want, and doing what your doing without the knowledge kinda scares me but its your project and not mine so here goes.

to check physical clearances between the piston and head you use modeling clay and cut it apart at the thin parts with a knife then guestimate the clearances. I'm not sure about BMW but in a regular racing engine you want at least .040 inch between moving parts which includes pistons, heads and valves.

I hope im not wasting my time here cause i am really trying to help you.

[535ise]

I hope im not wasting my time here cause i am really trying to help you.

No, you have been a big help to me, thank you !

[BigKriss]

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[632 Regal]

good point, you still should have squish area.

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