NEW from MI

[Garnet]

I bought them from an ex Boxerworks inmate from California. He ran them on his /2 conversion for about 10,000 miles then replaced the engine with an R100.

I planned on useing them with R75 heads and 78 RS 9.5 pistons on my /2 conversion.
More here: http://boxerworks.com/forum/viewtopic.php?f=1&t=648
I am not so sure now as my conversion is very nice as is with the R75 engine and the additional power will require a rear drive upgrade and a lot more brakes.

The cylinders will now probably find their way into my /5 at some point.

[mattcfish]

BMW Bayer says the compression ratio on the pre 9/75 1000cc Power kit is 9.5:1.
http://www.motoren-israel.com/products/ ... -1975.html

That's about the minimum I want to use with the 336 cam.

[Garnet]

Sooo... IF you where to buy the kit, once you have it and measure everything, it may well be possible to up the CR by at least a quarter piont by the use of a thinner base gasket or milling down the heads.

The kit will most likley have a squish band clearnace of about .050", I have read in a coulpe of places that .035" is safe and of course makes more power.

Did I ever tell you how much fun it is spending other peoples money?

[mattcfish]

Sooo... IF you where to buy the kit, once you have it and measure everything, it may well be possible to up the CR by at least a quarter piont by the use of a thinner base gasket or milling down the heads.

The kit will most likley have a squish band clearnace of about .050", I have read in a coulpe of places that .035" is safe and of course makes more power.

Did I ever tell you how much fun it is spending other peoples money?

.035"? What's the width of a compressed head gasket? Does that clearance include the gasket?
You would think, especially with nicasil cylinders, that all the aluminum would expand at the same rate and clearances would remain fairly constant.

[Garnet]

Yes, useing nicasil cylinders is probably where that reduction in clearance came from (only my gues). Doing a mock up with used head gaskets and clay or wax is the only way to measure it, like this: http://moragafalconers.org/bmw_pistons/ ... arance.htm

You will need to do somthing like that to check the valve pockets anyway.

I am hopeing some others will jump in here, as I am getting to the point where I am quoting others, and have no first hand experience with some of this.

[mattcfish]

I am hopeing some others will jump in here, as I am getting to the point where I am quoting others, and have no first hand experience with some of this.

Yes, this does seem to be our own private discussion.

[barndeadr80]

I was digging through stuff from a previous life and found some old catalogs from Luftmeister and CC Products. In the '90/'91 CC catalog, matching cylinder heads to pistons was a listed service. $50 a set back then. Anyway, San Jose/CC still lists a lot of headwork for airheads in their service section. Maybe someone there could shed some light on the subject.

[Garnet]

I was digging through stuff from a previous life and found some old catalogs from Luftmeister and CC Products. In the '90/'91 CC catalog, matching cylinder heads to pistons was a listed service. $50 a set back then. Anyway, San Jose/CC still lists a lot of headwork for airheads in their service section. Maybe someone there could shed some light on the subject.

Over the years BMW airheads have come with many different Piston/Head combinations. Aside from just the obviuos displacement differenaces, R100s had at least 5 different pistons and at least 3 different head shapes. This pictorial shows a few of the different R100 pistons and modifcations to a late R100 piston to make it work with the 1977 RS head:
http://moragafalconers.org/bmw_pistons/index.htm

Sometimes it is easier to modify the head to fit the piston, like this:
http://www.motoren-israel.com/popup_ima ... 41/imgID=0

All this is usually done in the pursuit of raising compersion, or useing the 77 RS heads to gain the 40mm exhaust. Sometimes someone (like me) wants to put ealier R75 heads onto R100 cylinders, just because I can.