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Wow. Lots of info to digest. Thanks guys. Next week I will cc the combustion chamber to determine the final compression ratio.
JohnMc, Cometic does indeed make a MLS gasket for the B18. Cometic advertises a compressed thickness of .047". They are available through R-sport. I have conflicting thoughts on whether I should spring for the extra C note for one of these gaskets.
Phil, the gaskets you are measuring are not in their loaded condition. Wouldn't they have a memory of their former shape and try to return to that shape when unloaded? Maybe use a dial indicator referenced to the block deck and measured to the top of the head after torquing it down to determine the distance from the block deck to the top of the head. The result algebraically added to a measurement of the head face to the same spot on top of the head would be the compressed thickness. I have never tried to do that but I reckon it could be done. I think it would be a lot of work for little reward.
George, In the scheme of things, I think I can safely ignore the volume of the area around the piston down to the first ring. If my calculations are correct, it works out to about 3 ten thousandths of a cubic inch.
I think it is much more important to set the quench height and then live with the SCR that results. That is why I am fretting over gasket choice so much. I really don't want to shave the head to set quench height.
B20Paul, I noticed a light miss at idle that seemed to smooth out as RPM climbed. I replaced the plugs, wires, and cap, in that order. The miss (actually a skip) got worse with each passing mile. Last Sunday night I was over at TexasAmazon's house and he had his compression gauge handy. My heart sank when I read #1; 60PSI at cranking speed. The others were 150, 160, 160.
I had suspected as much but didn't want to face the music. On the ride home it dawned on me that a burned valve would not smooth out as RPM goes up, it might be receeded. It was. In fact, all the exhaust valves were so tight I couldn't get a .010" feeler gauge on any of them. Number one rocker was holding the valve off the seat. I adjusted them to .017" cold. It sounds like a Singer now but it is running better than it ever has.
I know it is only a matter of time until I have to replace the head. It had only been 8K miles since I had checked the valves last. They were tight back then but I didn't think too much about it because they weren't that tight.
I've already got a B18 head. But a good B20 head is as difficult to find as hen's teeth around here. This is a repair and I need to make it as cost effective as I can. I am just trying to maximize what I've got to work with. I agree with you, velocity trumps outright flow for my purposes and I have never put a grinder to a head in my life. I have some common sense about the matter that I think would prevent me from destroying the head but I could certainly screw-up my port velocities. I have no access to a flow bench so I would not be able to quantify changes. I will leave well enough alone.
Thanks a lot for all the help. I will send the head out to the machine shop next week. I hope I don't have to use it for several months yet.
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Mr. Shannon DeWolfe -- (I've taken to using Mr. because my name tends to mislead folks on the WWW. I am a 51 year old fat man ;-) -- KD5QBL
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