One of the really cool things about working with a company like JE Pistons is that you can pretty much get anything you want, no matter how off-the-beaten-track your engine combination might be. Of course, odd bore sizes, pin heights, ring package combinations, and features like gas porting are all a piece of cake (and are often available for popular engines as shelf-stock slugs from JE’s SRP division), but what if you have some crazy super-secret head that just doesn’t want to work right with a conventional piston dome design? You’re going to need JE’s help, and they’ve outlined some tips for making combustion chamber casts that will allow them to precisely craft a dome to match your exact needs.

JE demonstrates two different casting methods, but whichever you choose, it’s important to use a material that’s both rigid and easy to remove. Flexible or brittle compounds like latex, silicone, modeling clay, or plaster won’t work because they can’t be scribed or measured accurately. Epoxy resin works great, except it may not release cleanly from metal (which sucks in ways that are easy to imagine). The right solution? Bondo, with a little WD-40 as a release agent, as it turns out.

Once the cast is molded, features like extended plug relief notches and flame slots can be cut in as well to further customize the dome of your piston. While 99.9% of engine builders and racers will never need to utilize these techniques to get the pistons they want, if you’re in that 0.1%, it’s nice to know that JE is ready to help.