260 Powerhead

[tabme]

I just picked up a 260 powerhead that i am going to go through and freshen up,I am going to do new rings,bearings,seals,clean up the ports. The exhaust chest is done already. I was looking for any Does or Don't on this powerhead and should i CC the heads to 34 or lower on this motor. Thank you

[Stoker boy]

Don’t forget to run a bore guage inside the cylinder walls. Should be close to 3.500
Its been a long time since I’ve run that low of compression I think a stock 260 is around 38 cc heads somewhere around 135 cranking compression. Depending on what your cranking compression is now if memory serves me correctly something like 5 pounds gain for every cc milled. I’m thinking if you go over 145 cranking you need to up the octane from 91. Don’t forget to have the injections serviced.

You might also index your fly wheel so you can check your switch boxes. Use a dial indicator 150,000 before top dead center will equal 25° and 0 is TDC.

[tabme]

Thank you for the reply Stoker boy--I have a real nice set of 32CC off a promax i was thinking of using with 120 gaskets just not sure if that's too much,wondering if 260s like a little more compression.

[Stoker boy]

I’ve never worked on a promax so I don’t know if those heads are interchangeable. I don’t know if the block has ever been decked. You can use a gauge or take the spark plugs out and use four pieces of Solder to check the squish area. I believe 120 are the thick head gaskets and the thin gaskets are somewhere around 50 or 55. It’s been my experience in the past that yes 260s like compression.
remember to pump up octane for higher compression. Different heads have different pocket sizes which can change compression but cc’s are the determining factor. If you want the motor to last just leave it at the factory specs use 91 pump gas and enjoy. If you’re looking to go out and give people a spanking you’re gonna be playing the modifying game.