Need Compression ratio input

[Ken Cooper]

Speeking with Jeff Prock on the phone the other day and he told me that my compression ratio should be 14 to 1. This motor will be 602 cubes with a 4.5 stroke and a 4.620 bore. Does 14 to 1 sound correct?

Being an N/A guy all of these years it's always been as much as possible. Right now this motor is 16.8 to 1 with a cnc digitized piston dome.

He also told me that there should be .170 between the valve pocket relief and the inner diameter of the top ring land grove. When I called JE they told they would put the ring groves at least .375 to .4375 down from the piston top. Can I check this with out cutting a piston apart?

[Zeke1]

I think the 16.8 is too high for juice 14 to 14.5 sounds right as for the piston if your ordering new from JE they should be abile to tell you the distance when you ordered and if you don't like it make them change it if your ordering customs to begin with it's no big deal

[Monty Mikho]

Speeking with Jeff Prock on the phone the other day and he told me that my compression ratio should be 14 to 1. This motor will be 602 cubes with a 4.5 stroke and a 4.620 bore. Does 14 to 1 sound correct?

Being an N/A guy all of these years it's always been as much as possible. Right now this motor is 16.8 to 1 with a cnc digitized piston dome.

He also told me that there should be .170 between the valve pocket relief and the inner diameter of the top ring land grove. When I called JE they told they would put the ring groves at least .375 to .4375 down from the piston top. Can I check this with out cutting a piston apart?

Ken tell me how your new JE pistons work out.. :roll: They changed casting about 1 year ago and you may want to look elsewhere for pistons.

You can check the ring stack height with a set of calipers. .375-.4375 is a little too much if ya ask me. .300 seems to be the norm for a nitrous motor. I had mine pulled .350 down and I didn't see any improvements at all for heat transfer into the rings. People are getting crazy with pulling the ring stack down. How far off do you have to be on the tune up to take advantage of the ring that far down? Give Bill Miller a call and pick their brain.. I think they will be a little more realistic in piston design. As far as compression? I ran the motor at 14.2 last season and 15.7 the season before. All I can say is give me compression for a better working combo... I believe the NPS guys are at 17 ~ 17.5 with a .34 pill. Some of them spray 2 kits in Orlando and seem to be the front runners... JMO