getrdunn

iTrader: (7)

This has been discussed before however what is the magic number on the piston below deck? This is debatable question and can ask 10 different people and get 7 different answers so the question is more directed toward SC builds with hands on experience. At the same time what is considered a good target quench. I have my own experience with such however on lower hp builds and mostly NA builds. 555 SC 8.5:1 comp build.

NA I'd typically be btwn 005-008 in the hole with .040 gasket with a total of .045-.048 quench. seems like many engine builders try and end up with 0 to .010 deck height to help avoid detonation. SC being a little more forgiving??? Forced induction and chambers can change things up but how much?

253

Keep the Quench between 34-38 for less detonation, I just finished an engine that piston was .008 down in the cyl., used a .027 Cometic head gasket , I have build many engines, all NA., with Quench in this range, never had any problems.

mike tkach

iTrader: (3)

i usually look for.050 but a little less will do.

getrdunn

iTrader: (7)

That's seems to be middle of the road. I wasn't sure if an sc application with more turbulence so to speak would have an affect or not. Plus the chambers are going to be reworked and opened up regardless so would more help or not? Just a thought that popped int o my head. Jim v tried steering toward flat tops but just don't see any good way to get 8:5.1 or less without some kind of other potential risk. Personally I've always liked flat tops when able to use just cause of the even combustion. May not mean chit in the real world but always made sense to me. That's only when comparing to higher dome pistons though. Almost like side loading. Anyway I'm getting off track here.

mike tkach

iTrader: (3)

as you know different builds will require different pistons.if i am building a pro charged deal i like more compression because the unit needs to be spun faster before it makes boost so it needs to make more power before boost.a roots or screw blower makes boost as soon as you start to open the throttle blades.the total amount of boost and the engine application needs to be be thought out before deciding on a c/r. on a pro charged 565 i built last year the c/r came in at 9.2 to 1,if i had that one to do over the c/r would be closer to 10 to 1.

getrdunn

iTrader: (7)

Ya I'd like to have my static mid 8's + or - but I was more so wondering about the quench and the deck height. Looks like I would end up with 20 -22cc dish regardless so I'm not going to be concerned with deck height at this point.

Unlimited jd

iTrader: (5)

Just for reference, merc 1075's use a flat top piston just over .100 in the hole

ezstriper

the best is 0 if you can get the compression where you need @ that

snapmorgan

iTrader: (2)

I like them around .010 in the hole with a .040 gasket. Has worked well for me

mike tkach

iTrader: (3)

with a new block i almost always go .010 in the hole,that way if it needs to be resurfaced down the road for some reason you still have some metal to machine on and won,t have the piston out of the hole.