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Discussion Starter · #1 · (Edited)
I had the head skimmed on my 85 SPG a few years ago when the head gasket blew and the head warped. My fuel economy and low end power have suffered ever since. The cams were retarded by a few degrees because of the head skim but it took me a long time to figure out that this was causing a power drop. The car ran ok but off boost low and mid range power was not acceptable for a daily driver. Power was also a little flat under boost until it reached the higher rpms where the power picked up and didn't trail off at redline. For a daily driver the lack of low end torque was unacceptable and just not as enjoyable. I installed DrewP's adjustible and indexable cam gears (http://www.saablink.net/forum/showthread.php?t=47799) yesterday. The indexing feature is absolutely fantastic. I was able to dial in exactly 2 degrees of cam advance to bring the timing marks to the stock setting. The car is now much more enjoyable to drive because it actually has some torque, and it requires less effort to get up to speed, fuel economy should also be improved. The cam gears are well made and precise and having the ability to index the cams precisely is what makes these cam gears brilliant. I would highly recommend these if you have the head skimmed. They should be fun to play around with too. Great work Drew!



 

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Different thickness head gaskets are not available unless you go for copper, but then you have to mess with o-ringing the block/head and I'm not even sure if anyone makes them anymore.

Best,
Drew
 

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A 'regular' fiber head gasket has metal inserts around the cylinder bores - they're sort of like U-shaped rings. When you torque the cylinder head down the little 'U's' crush down, and the crush tension is what seals the cylinder bores to the head so that the combustion chambers hold pressure. This is also why head gaskets aren't reuseable - once the crush ring is crushed it won's seal again if you take the tension off.

With a copper head gasket the whole gasket it copper, so there is no crush ring to seal the cylinders, so you have to add in a feature to create the seal. 'O-ringing' the block means you machine in a little groove around the top corner of the cylinder, and install a little metal ring that will 'cut' into the soft copper gasket material, and creates the seal. This is why copper gaskets are reuseable, but getting it all lined up again can be a headache, plus you have the extra expense of the machine work to install the o-ring seals.

http://forums.bimmerforums.com/forum/showthread.php?t=1072411&highlight=oring+block&page=2



Best,
Drew
 

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Thank you for the explanation.
Only thing I don't understand is why the copper gasket is reusable. Once the metal rings press a groove in the copper the gasket shouldn't be good for another use in theory.
Has anyone put a copper gasket on a B202 ?
 

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Just use a stock gasket. Always hard to seal the coolant/ oil passages with copper. Unless you require something that will seal a 94mm bore etc.

Cometic installed exactly as they instructed. We went back to a stock one and worked perfect. Unless we can get 100 orders and get them to make custom bore MLS gaskets like the 2x5 motors no need.
 
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