Jeep Strokers

.030 overbore
0 deck ht
.043 quench
5.875 rods
Comp 68-232-4 cam
64.2 cc chambers (raised roof from hot 4.2 liter build)
I want to run 87 to 91 octane.
I use to run 9.875 SCR and 8.4 DCR using hypereutectic pistons but that was with 3 2bbl Webers and distributor I could tune. It ran good on 87 octane and great on 91 octane. Since the stroker will be computer controlled and not an IR intake & mechnanical distributor I wont have such good control over mixture or spark advance.

I have two choices in pistons, Sealed power hypereutectic H802cp/H825cp 15.1 cc (9.67 SCR/8.31 DCR)
DCR seems high for 87 octane.
or
Sealed power cast 677P or 525P 17.5 cc (I will adjust deck for .043 quench) giving a 9.44 SCR and an 8.12 DCR

The cast pistons seem much better for getting an 87 octane motor but I have never built with cast pistons at this high a compression ratio before.
Two questions:
1) has anyone run a cast piston in a stroker at 9.4 or greater SCR?
2) has anyone had a problem with a cast piston at this SCR?

For what its worth here is a summary of posts on SCR-DCR Quench and octane on the board.
SCR/DCR/Quench/octane

9.2/7.96/87
9.875/8.51/.050/93
9.25/8.03/.080/91-87 blend
9.25/7.8/.043/87
9.4/8.0/.048/89
9.25/7.8/.043/87
9.6/8.1/.043/87 (bratcop, chip and tuning)

Seem to recall a post on the old Yahoo stroker group about someone enlarging the piston dish to something like 23 cc. I will see if I can find a bookmark.

BTW, loved reading the porting thread! Did you ever get to recheck the head here in this post?

nosigma wrote:1bolt

I just pulled down my Rambler motor due to a bad over rev (7200 rpm) which caused a vibration. Since I have the head off I would love to get it flowed after I clean it up and see just what I ended up with using the bigger offset valves. If your still have the flow bench up and running let me know so we can get this head tested.

John

Here is a link on enlarged dishes:

http://www.jeepstrokers.com/forum/viewt ... =dish#p828

I did get the head flowed . It showed us a little worse than a stock head. Thats a flow bench problem, not a head problem. I was given my money back.

On the 258 build that am taking the crank and head from I ran hypereutectic pistons where I machined out the cups at home on my mill to get the volume just right. I have since sold the mill. I wanted to avoid having to customize pistons. Still hoping to see if anyone runs or has had any problems with cast piston at 9.4 scr or higher in one one of these motors.

John