383 wisdom

[Stryder67]

hey all. I'm putting together a 6 inch rod 383 and need piston opinions. I'm leaning toward KB performance pistons (link below). however I have heard that in order to keep the pistons together the top ring needs to be gapped bigger. wouldn't you lose power from this? suggestions on gap? I am open to suggestions for other pistons as well. also in the description on summits site it says spacer ring included. what does that mean?
Description on engine:
eagle specialty 6in I beam rods
scat series 9000 6in stroker crank
lunati voodoo 233/241 @.50 .504/.525 lift 110lsa
https://www.summitracing.com/parts/u...-030/overview/

thanks in advance

[B. W.]

In perfect world you would run zero gap but, in real world, as the ring heat up it grows so you want enough gap so that at operating temp the two ends don't touch. If they do the ring breaks.
So, the the top ring gets hotter, it gets more gap. But, it's a fine line - too little gap on the second ring & it will build pressure between the rings & lift the top ring. I've set gaps various ways but but I'd just go with what the manufacturer recommends. you could gap top ring & second the same and it wouldn't make much difference for a daily driver.
It would be a fun experiment if you were bored, had a dyno & lots of money to see the difference ( or lack thereof) in power with various end gaps. (Someone probably has done this)

[Stryder67]

thanks for reply. so if one were to run nitrous on this engine (not planning, just curiosity) how much more would you have to gap the rings from the manufactures specs? Kieth Black recommends .026 for naturally aspirated street motor.

[Marv D]

Your going to hit those hypereutectic pistons with a shot of N2o????

Myself I wouldn't buyKeith Black anything. When Keith was alive the company made a GREAT product. Now it's a marketing name that is being taken advantage of. They are fine for a low compression, low RPM daily driver,,, IF you have the machinist fit the bore to each piston.

Buy a SRP and you have a quality tooled piston that EVERY piston measures the same to 1/4 thousandth, , you bore the block right, and everything fits like its supposed to. AND a nitrous shot deserved a forged piston. You get what you pay for.

[ka_jd7and1]

Street towing or street nitrous is .032 gap.

They have a chart in the catalog on how to calculate correct ring gap for your application.

We have used KB hypers in our dirt track motors as a cost effective piston with good results. Have not popped a piston due to ring issues. I always hear about people that do, but it sounds more like they are not following the recommended ring gap and gap them too tight.