Trying to figure out what compression a 393 will have with flat tops with 2 valve reliefs vs 4 valve reliefs. I want to be able to run premium fuel and not have to add racing fuel. The heads are 69 cc chambers

 

It's AMAZING what you can find on the web these days.....

http://www.rbracing-rsr.com/compstaticcalc.html

 

thanks that was a big help

 

with cast iron heads you dont want to exceed 9.0-1 compression. some squeek by with a bit higher but not recommended. with aluminum heads you can almost hit 10-1 but 9.5-9.8 is safe.

 

your cam will have a big effect on how much compression you can run.

it's all about the combo

you don't want to run a cam with 244*@ .050 with 8 to 1 compression it will be a dog big time until it start building cylinder pressure.

same goes with a 10 to 1 compression motor, with a 208* @ .050 it will ping like a bitch.

it all has to match to work right......

I've seen guys that want that big cam sound so they buy a cam that gives it to them but they do nothing about the compression. they bitch because it's a dog off the line and don't make any power until 3000.

most cams will come with recomended compression ratios.

figure out where you want it to run...pick a cam that will get it there ...and then build your compression to match the cam.

give Cam Research a call all he does is FORDS

 

Scroll down on this ebay add and there's a table listing cr's for different stroker/piston/head combos. A 393 w/ flat tops and 69cc chambers shows ~ 10:1

http://cgi.ebay.com/ebaymotors/FORD-...spagenameZWDVW

 

[QUOTE=BaronVonAutomatc]Scroll down on this ebay add and there's a table listing cr's for different stroker/piston/head combos. A 393 w/ flat tops and 69cc chambers shows ~ 10:1

http://cgi.ebay.com/ebaymotors/FORD-427-393-408-FORGED-STROKER-5-0-351W-MUSTANG-TMD_W0QQcmdZViewItemQQcategoryZ33620QQihZ008QQitem Z180090850816QQrdZ1QQsspagenameZWDVW[/QUOTE]

Now stick the pistons .009 out of the block and see what you have. I bet it's up there....

 

Ok I ran it on Desk Top Dyno to get the compression for you.

69cc head
.041 gasket
-.009 deck (piston sticking out of the block)
4.030 bore
3.850 stroke

flat top piston no reliefs 11.63
-10cc dish......10.39
-15cc dish......9.88
-20cc dish......9.41
-25cc dish......8.99

hope this helps.........