piston weight vs compression

I'm considering trimming the tops of the pistons to help get some weight off. What's more important, weight or compression? this is blown akly with roots in truck & tractor pulling. thanks guys for any help pro and con

 

You don't have to take the weight off the top, You can take weight off the inside of the piston, some right under the wrist pin boss, some from the inside top of the piston. You might want to call whoever made your pistons and see how much you can take off, I know Venolia dose that to there pistons if you ask them to do it when you order them.

 

The piston people say that machining/lightning on the piston can/will change the shape of the skirts. They prefer to do it themselves, but heck, who hasn't touched them up.
We had Venolia lighten ours to the max when they made them for us. Our last set was .025" bigger and .5 point more compression and it had the same weight as before. Therefore we did not change the crank balance.

 

I already plan to take it out of the inside of the piston, but some of my pistons have a valve pocket that could be trimed flat (some are already that way). I've got them weighting all the way from 890g to 720g. the heaviest and lightest are both from a-fuel motors!!

 

I would not sacrifice compression for weight.
What got you thinking to reduce the weight of some pistons but not all?

 

those weights I'm listed are pistons of different sets. I'm going through some of the boxes and boxes of pistons I've got trying to get motors ready for next season.

 

Lucky, don't know what kind of RPM you guys turn but I'm thinking it's quite a bit less than most of the TAD and TAFC guys are running. If you're in the 7500 range, don't believe piston weight is as much of an issue as having a little more compression. Since you guys are running for a longer period of time with a lot of loading, seems like it would be best to keep the piston as strong as possible. JMHO

 

my last motor death had the heaviest pistons and pins and I felt they helped pull the rod apart.. I've been running in 8000 plus range (8800 chip) but there's a couple kb's going 9500+ and kickin' butt. was looking at pistons again this evening and the heavier ones have alot of dome meat

 

There are a lot of variables, depending on your combination, could use more info, stroke, rod length, head cc's. Fuel heads take a lot more piston dome than a fat-head which ='s more piston weight. Big inch motor like you guys run might be able to get by with shaving some weight off the outside and still keep your compression up with a thinner gasket. Just food for thought.

 

a couple of quick variables......4.5 stroke, 7.25 or 7.50 rods my motors are arias/fontana so the chambers are kind of standard, valves maybe 2.4 to 2.6. So of these pistons have deep valve pockets and looks to me like shrouding that I felt could be trimmed and maybe that would be good for flame travel.... Alot of my feelings are not run what you brung but run what I've got.... again would I hurt power too much giving up some compression?? Where's the breakover point? thanks

 

hey Lucky...do you know any of the Nation's Ld or Melvin or Craig?

 

yep....some of these things had their turn there....Craig's gone to Veney now