top ring land location

[hbstang]

what would be a safe distance from top of piston to top of first ring?right now they are .140 down.
these are out of a 427 stroker short block i have.would they be ok for 550-600 hp n/a 454?

[Barry_R]

Were they made that way - or are the tops cut?
Were the valve pockets cut deeper?
Dimension should be OK, just concerned about valve pocket to back of ring groove dimension.

[hbstang]

i think the pistons were cut that way.3.98 crank in a 427 block.venolia pistons with small dome.this engine was built maybe 20 years ago?will they hold up with 550-600 hp?

[jayb]

I'd share Barry's concern about the distance from the ring groove to the valve cutout on the top of the piston.  If that is at least .100", you should be OK to 550-600 HP.

[machoneman]

Great to check it as noted but I wonder if a top flight outfit like Venolia would cut a piston and ignore their own minimum safe distance, whatever they used back then. Guess you'll measure same and tell us. 

[Joe-JDC]

You need a mininum of .180" thickness under those valve reliefs, or it will melt when it gets hot.  I ran that similiar combination for years.  427 piston cut for 3.98" crank.  Joe-JDC

[Barry_R]

Should be good.  Question stems form the modification process.  When the trimmed the dome end they may also have cut the valve pocket deeper at the same time.  Its the intersect between the inner/lower corner of the pocket and the root of the groove that'll catch you....

[hbstang]

thanks for all the replys,but now after pulling the top ring out,there is no way it has .100.back side of ring land is .200 from od.the exh may have as little as .030 between ring groove and pocket where they intersect.also,top rings are .041.maybe a bbc piston?here is another pic.also in the pic,the scribe line is the approx back of ring groove.so now i need pistons!

[CaptCobrajet]

I think I'd probably run that.  Those pistons were most likely made for a 3.98 stroke, being that they are domed pistons to start with.  If they were flattops, I might worry more about deck thickness.  From your pics, the VR are not very deep, and .140 down is pretty darn safe.  I used to run .125 down and huge VR in Super Stock 428's.  The exhaust relief was thin in the corner, but we never had any issues.  The key part of your question was the part about being naturally aspirated.  Any kind of power adder throws everything I just said up there out a 40 story window!!