I am putting a l28 back together and trying to get a good strong running engine. New pistons, bearings, bored 20 balanced, mild cam, headers, ect. The question is about putting the thinner 1mm head gasket on. Is it worth it for the slight bump in compression? I wanted to put f54 block pistons in but couldn't find them available anymore. Motorsport has a gasket and I have heard about one from Felpro. Any suggestions will help. Thanks.

You didn't say what head you're using nor which pistons you went with (flat top or dished). The stock gasket is 1.2 mm and the Felpro is 1.0 mm. I've used Felpro and had good luck with them but there are others who haven't.

Unless you're running an N42/N47 head with flat top pistons, I'd go with the Felpro. But to be sure, use lengine.exe to calculate the CR with your configuration. If the CR is going to be around 10:1 with the stock HG, there's no point to pushing it higher - backing off timing to prevent detonation costs more HP than you get from the extra CR.

I am running a n42 head with dished pistons. I tried to get flat top but was unable to locate any. Are they discontinued or did I not look hard enough? I was on one engine calc and came out at about 8.5 with a 1mm hg. 8.3 or so with the stock. Is it worth the dollars for the small bump in compression?

ITM makes flat tops for the L28.

Why do you think it will cost more to go with a 1 mm gasket? In my experience, felpro is often the least expensive, less than $30 at Autozone or Checker. I don't think you will notice any difference between 8.3 and 8.5, but unless you already have the thicker gasket, why not go with the thinner one?