Even the dished pistons will have quench effect if set up for a proper gap as either:
- the piston height can be set so that outer edge of the piston crown will close up close to the head's closed area surfaces
- or the area above the eyebrows will close up tight to the head like in a normal quench space.
Quench usually gives a bit better combustion efficiency, but the main benefit to seek is for improved detonation resistance. I always want that, with the way I like to set up engines for my uses (with DCR at 8 or a bit higher).
You can go on the SCAT site and go through their parts selector here:
Rotating Assembly Product Search - SCAT Crankshafts
Enter 6.123 for rod length and it will give you all the SBM stroker kits. The Icon and KB dish/eyebrow volumes are all given as negative numbers. (Be aware that KB and Icon will list the same volumes as positive numbers.) You can deduce the piston PN's from that. Hypers will be KB's and forged will be Icon's.
The SCAT listings' dished forged at 20.5 cc's are very probably Icon IC984's with the dish and NO step on top of the piston crown in the quench area referred to in post #3, and so will not stick up above the stock Magnum deck height. These pistons have a littler lower compression height to work better with the .015" shorter deck height of the Magnum block. But they will not have quench unless you mill the deck OR you use .028" thick Mr Gasket 1121G head gaskets to get a quench gap of around .047".
Next choice is the IC745 with a .020" taller compression height than the IC984's. They will stick .003" + or - above the stock Magnum deck, and with a Felpro 1008 head gasket at .039", will give you a .036" + or - quench gap. A Felpro 8553PT head gasket will put you at about a .047" quench gap.
A 3rd choice is the KB416 which is like the IC745 with a bit larger dish. You can ask SCAT if this is an option.
Here are various combinations with SCR and quench gaps + or -. I say '+ or -' as the actual deck height will usually have some variations.
- IC984 and 1121G gasket: 10.0 SCR and .047" gap
- IC745 and 1008 gasket: 10.3 SCR and .036" gap
- IC745 with 8553PT gasket: 10.0 SCR and .047" gap
- KB416 with 1008 gasket: 9.8 SCR and .047" gap
- KB416 with 8553PT gasket: 9.6 SCR and .047" gap
Keep in mind that the deck heights will vary across the block, so it would behoove you to measure this up front. You can get decent numbers for this with the stock crank, a stock rod and piston with rings removed(where you use the standard piston CH and rod length), and a dial indicator up on the deck.
