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Discussion Starter #1
I was ruminating on the depth of the quench band in my rebuilt B20E. I used the Elring gasket set sold by IPD and was just looking at the Elring website and it appears that the gasket is listed at 1.2 mm thickness (0.047"). I always thought that the stock gasket thickness was 0.028 ". If 0.047" is the compressed height of the Elring gasket, my quench band is probably in the order of a rather useless 0.067".

Does anybody know whether the heights listed in the Elring catalog are uncompressed or compressed thicknesses?

The thinnest gasket that I have been able to find is a Cometic MLS gasket at 0.027" I am assuming that is the compressed height; but, the catalog is not specific. Does anybody know? Is anybody aware of a thinner gasket than the Cometic 0.027" gasket?
 

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The E originally used a .8mm gasket and the F a 1.2mm. For years now, they've only offered the 1.2 for both E and F engines. What I do is use the B20B gasket, which is nominally .8mm. The larger injection combustion chambers intrude very slightly into the fire rings on the B, but I've never had any problems with that.
 

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Discussion Starter #3 (Edited)
Thanks Phil. I take it that the thickness that Elring, Cometic and others quote is the compressed thickness of the gasket?

0.8 mm works out to a hair over 0.031". My pistons sit about 0.018" below the cylinder deck. With the F gasket that I probably have, my quench band is probably around 0.065". I have very slight detonation right around 3000 RPM under wide open throttle which I think might be due to a worn distributor. The static timing is 10 deg BTDC climbing to a max of somewhere around 32 deg BTDC; but, is very unstable, bouncing over a fairly wide range. If my detonation problem is not purely due to a worn distributor, do you think there is any upside to trying the thin Cometic gasket to reduce the quench band to something around 0.045", or is that still so large as to be ineffective?
 

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I was using round numbers -- the Elring B gasket crushes to .033" or .034".

Opinions vary a lot on what the optimum clearance is. I'm in the David Vizard school in which tighter is better. With stock rods, I go for .032" clearance as being safe, so I deck the block so the pistons are .002" out.
 

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Discussion Starter #5
Spring will have to arrive before I get a chance to try my ignition fix (ditching the coil and distributor for some COPs). If I have to do some silly ignition mapping and radically retard the timing to eliminate the detonation, I might try the thin Cometic gasket (Head R&R is fairly easy. I really don't want to have to pull the block to send it out to be decked).

Are you aware of anything special or mysterious about the installation of the Cometic gaskets? I couldn't find any application notes on their website.
 
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