I posted this in LT1 Tech, but didn't get any good replies.



I have had these pistons for a while and just got around to looking at them. Will the way the top is made be bad for good quench? Instead of it being a flat top with a dish, it has a beveled edge. By looking at it, you'd think some of the mixture would be trapped at the outside of the piston.

Thoughts?? Am I way off base here??

 

I personally would not buy this piston for anything. The bevel allows combustion in close proximity to the rings, which weakens the ring land & also transmits more heat to them. This is patterened after a late 70's early 80's emissions piston. This beveled area will not provide effective quench, nor will combustion be that great in this area. If you also look at this piston, the oil ring groove is slotted for oil return vs. drilled as many performance pistons are. This makes it cheaper, but much weaker than a good performance piston. I've seen these pistons deform at the oil ring groove under high HP applications. Do yourself a favor & look for a D-dished piston if you need to lower compression. They will offer better quench as well as improved ring support.

 

I already have them, I was just wondering if I should use them.

 

They cam out of a supercharged 355 making ~615 rwhp. 9:1 SCR. I don't guess he had any detonation problems?

 

So, I guess I shouldn't use them for ~8+ DCR?!

 

Anyone have anything else to add, or did Lonnie pretty much sum it all up?

 

I'll say that Lonnie's comments are basically what I would have said. Factory style emissions-era pistons were like that. The LAST thing the factory wanted back then was any quench or other cracks and crevices for air/fuel to hide out in and cause higher HC emissions. So they did a full-face dish and a beveled edge above the top ring. I can't really see the oil ring return holes/slots from that picture but I agree that most performance pistons I've seen tend to be drilled, not slotted.

 

Funny how this is TRW's forged piston that they KNOW will be used in high HP applications, yet they design it like that!