The black gasket wasn't just something JAE sourced off a shelf. They went to a gasket manufacturer, paid for tooling, and had it produced. For the first run, they went with temporary tooling, and there was a problem with the registration of the fire-rings around the inside of each bore hole. You might be able to build a case for some blown gaskets being due to that.
For the next & subsequent production runs, they paid for permanent tooling that resolved the registration problems. Unless you've been sitting on a first-run black gasket, there aren't any more in the system.
The later JAE black gaskets are supposed to be comparable to the Goetze brown/ gray-green (olive drab) gaskets, but I don't have any test data that quantifies performance for either of them.
One thing I'm curious about is the compressed thickness. The Goetze gasket's compressed thickness is about 0.5mm (0.020") greater than the original steel-asbestos-steel gasket. As a result, the cylinder head ends up sitting that much higher up off the block deck, the combustion chamber volume is increased, and the compression ratio drops by about half a point (8.0:1 becomes 7.5:1). When the Goetze gasket was introduced in Jan 1993, Lotus simultaneously changed the block spec, machining the deck height lower by that same 0.5mm (0.020") in order to compensate, and seating the liners a similar amount deeper to maintain the correct 'nip' (liner exposure above the block deck). So all new engines produced from that time forward maintained spec compression and power; while all old, existing engines that were rebuilt with the Goetze gasket lost half a point of compression and some power.
Anything that changes the distance between the crank and the cams alters the amount of slack in a loose timing belt. Then when the tensioner is tightened, the slack in the exhaust side of the engine gets pulled up and over the cams to the tensioner on the intake side. Cutting the head to flatten a warped bottom puts extra slack into the belt, which results in both cams being slightly retarded when the belt is tensioned. Installing a Goetze gasket with it's thicker compressed height reduces the slack in the belt, so less slack gets pulled over the pulleys, and both cams end up slightly advanced. If you can't figure out why your cam timing marks don't align perfectly, the answer might lie in the amount of slack in the belt when loose (cut head/ fat gasket).
I would be curious to know if the JAE black gasket has the same compressed thickness as the Goetze part, or hopefully, thinner... more like the original steel-asbestos-steel gasket. That's probably just wishful thinking.
Last edited by Esprit2; 03-17-2018 at 05:42 PM.