Fly cut clearances

[kansasfirstgen]

Filled block with .016 piston to wall clear. Cast pistons and .100 over valves with 8mm stems. I have mocked up and cut .250 deep pockets in an old piston giving myself .125 clearance on each side of the valve. This seems excessive, but the more I thought about it maybe the larger diameter pocket will help with moving air around the face of the valve. What is standard procedure on a sloppy, high rpm motor? How much bigger should the pockets be then the valves? Thanks, AJ

 

[kansasfirstgen]

bump

 

[cumminsman315]

I've not setup any on a diesel but on the last motor we did .050 bigger than the valve. Motor turns 10,300rpm

 

[kansasfirstgen]

We do .050 to .060 as well on a gasser. I am worried about the piston rock with the sloppier piston to wall clearance. Thanks for the input.

 

[zstroken]

I am kind of curious why your filling a block and still using cast pistons. I would think if your gonna turn it hard enough that you need it filled, that the cast pistons won't survive.

 

[BRE]

I am kind of curious why your filling a block and still using cast pistons. I would think if your gonna turn it hard enough that you need it filled, that the cast pistons won't survive.

This, screw cast pistons. Can we get some more info on the motor?

 

[kansasfirstgen]

Thanks for the encouragement toward cast pistons haha. The motor is nothing special, just one I am putting together for local bush pulls. Filled block with cam bearings and fire ringed block and head with studs, 5/8 girdle, .020 over 286110 pistons delipped, tapered, cut .250", and will be coated. Polished and peened, balanced rods with arp bolts. Ported 12v head with .100 over ss valves, dual springs, ti retainers, 10* locks, runner intake. .370 lift cam with plans of roller rocker next year. 5x.020 injectors, 13mm 215 pump if I have time to get it built, fed by a magnafuel gear pump off the cam gear. 80mm over 64mm t4 ew for now, a/w cooler and water injection if I need it. Sorry for the giant run-un list. This is what I can think of off the top of my head. All to be put together in the next 4 weeks lol. I will throw it on the superflow engine dyno at work if someone will let me borrow a cummins to chevy bell housing adapter!