Piston accumulator grooves

[volodkovich]

Hi all,

I purchased these cheap Keith Black performance hyper pistons for a performance street engine build. They've got a really large accumulator groove, more than I have personally seen on any performance piston. Can anyone shed some light on why they'd be this big and if there is anything to look out for when running them?

Engine is a hot street 4 cylinder, 11:1 CR pump gas, 3.445" bore x 3.62" stroke, 7500rpm limit. Rings are 1.20mm x 1.20mm x 3.00mm

Cheers!

[englertracing]

The Piston has no valve relieves which allow for a relatively High top ring minimizing crevice volume- which is a good thing. they have a really tall compression height which allowed them to put the 2nd and Oil ring far from the compression ring allowing that large accumulator Groove. I don't see anything wrong with the large accumulator Groove

[Walter R. Malik]

Hi all,

I purchased these cheap Keith Black performance hyper pistons for a performance street engine build. They've got a really large accumulator groove, more than I have personally seen on any performance piston. Can anyone shed some light on why they'd be this big and if there is anything to look out for when running them?

Engine is a hot street 4 cylinder, 11:1 CR pump gas, 3.445" bore x 3.62" stroke, 7500rpm limit. Rings are 1.20mm x 1.20mm x 3.00mm

Cheers!

Just be sure that the top ring gap is wide enough.

[rebelrouser]

I have used the KB Hyper pistons on a lot of street B and RB engine builds. Your picture looks a lot like the Chrysler big block pistons as well. I make sure the end gap is big enough and take out a few degrees of timing, keep the RPM's down to around 6,500 max and they lasted very well for me. I ran 10.90 et 440 Chrysler bracket engine for 6 years with out freshening and when it broke it was a broken rod that done it in, piston was still in the bore in one piece. I also did a SBC, with a 671 blower for a mini rod tractor puller with the KB's as an experiment, it also did very well even with the blower. It ran two seasons until he got the money to build a better engine, actually won a couple events.

[Mark O'Neal]

It's large because the land is large. The theory is that you want less pressure between the top and second than you have above the top.

It's a left-over from the days when the rings were gapped backwards....but much of piston (anything actually) "design" is fashion so...there they are.

[volodkovich]

Thanks guys, much appreciated!