Originally Posted By: moregrip
Originally Posted By: CNC-Dude #5585
Originally Posted By: moregrip
Question: who offers a 6.2 rod and forged piston for the 250?


Most all connecting rod companies offer them as a custom part, but also at a custom price. 5.700" and 6.00" are the norm for the 250 engines for off the shelf, modest pricing rods.

As for piston sizes, you will rarely find a 250 or 292 that will clean up at .030" over, and i've seen many that had a couple of cylinders that wouldn't even clean up at .060". The front 2 cylinders are the worst ones typically. So find a block and get it rough bored first to verify it will clean up at an acceptable bore size before buying pistons.

You seemed surprised at the cost of pistons, many people expect that building a 6 cylinder is somewhat cheaper than a V8 because there are 2 less cylinders. Its often considerably more and even with less HP than you'd get with a V8 unfortunately. So don't let cost hinder you.


not really shocked by the price just kicking myself for not buying a set of forged 307 pistons when I had the chance a few years back!






Not all forged pistons are created equal. For the expected boost level you are seeking, you need a very premium quality piston forging, and TRW doesn't offer that in the 307 style pistons. You need a true forced induction aluminum alloy and specific piston die to create a piston forging that can withstand the constant cylinder pressures of 12-15 psi. The TRW's will only last for the short term, but soon fall victim to being subjected to use it wasn't designed or intended for. For forced induction, you need a 2618 grade alloy piston. You can also get other custom features to ensure longer piston life with a custom piston that you won't get with an "off the shelf" piston like the TRW.

Even companies that manufacture MLS head gaskets only rank it in the middle of the pack for sealing ability for forced induction compared to copper gaskets and o-ringing, which they highly recommend for that type of usage. Plus, MLS gaskets require some more specific machine work that makes them less forgiving if these procedures aren't followed also. And not all machine shops are capable of performing these tasks, so make sure your machine shop has experience with them and knows how to follow and perform these tasks because the gasket company many not honor any warranty issues if the block and head aren't prepped correctly.


Class III CNC Machinist/Programmer