SB Scat Stroker Kit - Compression??

[340sFastback]

I am planning to build a .020" 340 stroker with the Scat cast crank stroker kit part # 1-98013BI:

http://www.strokerkits.com/new_page_6.htm

Summit will sell me the kit and they say they can get it with the .020" over pistons.

Question:

The kit says 9.7:1 compression with 64cc heads. When they come up with that compression estimate are they assuming zero decking the block and .040" head gasket? I just don't know what assumptions they use to come up with that number?

I am planning to run Edelbrock closed chamber 63cc heads. I have heard they actually measure out around 65cc. I am looking for 10.5:1 compression to run on pump gas premium. I am also planning to have the block decked. Any advice greatly appreciated, thanks,

 

[jysnflem]

I'm running a 415 stroker that INDY built the bottom end. Zero deck block and pro tru dish pistons. The pistons have a small area that's dished on the bottom and flat near the top. When I had the heads done they were measured for how many cc's each chamber had and then equalized to the largest chamber by grinding material out of the smaller chambers. Once they were all the same they calculated how much to machine off the head by measuring piston dome volume "for the litlle dish I had", and head gasket thickness etc. After the heads were machined he remeasured them and they were 62 cc heads. My engine ended up being 10.2 comp. If you have flat top pistons and zero deck your heads might need to be 63cc. to have 10.5 Your edelbrock heads should be 64 mine varied 64 to 65 when we started. Jysnflem.

 

[jimmyray]

Your edelbrock heads should be 64 mine varied 64 to 65 when we started. Jysnflem.

Same here. My Edel Perf chambers CC'd at 64 and 65.

My compression as calculated by Hughes engines was 9.9, but the Keith Black wesite calculator has it at 9.6. I should have gone higher, maybe to 11. I run 93 premium and have *never* had a ping, and my last tank I mixed 1/4 93 to 3/4 89, still no pinging! If I had to do over, I would push towards 11:1 compresson with Aluminum heads and pump premium.

 

[340sFastback]

Thanks for the advice. Very helpful.

 

[340sFastback]

I called Scat and yes they assume zero deck and .039" head gasket. The dish in the kit is 20 1/2cc and they tell me that will give me 9.7:1. Scat says if I want a smaller dish volume it would have to be a custom piston. Flat top piston will put me over 11:1. I discussed this with my machine shop and he really doesn't like the idea of going any higher compression for a pump gas motor.

 

[Brambles]

What about using the flat tops and leaving he pistons down in the hole enough to take you to where you want to be compression wise? Maybe increase the valve relief in the pistons, that might bring it down enough?

Just some thoughts

 

[340sFastback]

What about using the flat tops and leaving he pistons down in the hole enough to take you to where you want to be compression wise? Maybe increase the valve relief in the pistons, that might bring it down enough?

I really want to have a .040" quench combustion chamber for increased power. The quench chamber also helps to fight off detonation. If I put the pistons down in the hole that will increase the quench area volume and I will loose the benefits of the quench combustion chamber. I am probably only loosing 20-25 hp going with the lower compression but I will never have to worry about running on pump gas. This is primarily a street car that may only see the strip a few times. If it was a more strip oriented car I think the high compression pistons would be the way to go.