hey fellas, i tried those two online DCR calculaotors and one of i felt didnt give me a solid answer for my DCR. heres my combo

4.030 bore
3.75 stroke
5.7 rods
flat tops with -7 CCs of valve releafs
Zero decked, head gasket bore and thickness 4.166 .039

heres my cam specs
http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=12-223-4

BUT i have 1.6 roller rockers. i beleve my SCR is 10.8:1

I tried the both as well, pat kelley's shows 8.53:1 and rcr shows 8.53:1 @ sea level with 172 psi 8.33:1 @ 1000' with 167 psi. from what I can tell these numbers should be fine on pump gas.

The 1.6 rockers do not appreciably effect the cam duration or valve open/close points.

thanks fellas. some im right at the limits of pump gas eh, exalant

Try this witha flat top with no valve reliefs and see what you get. I belive a better option might be a smaller chamber with a D shaped dished piston. You can get more quench in the head and promote better a better burn and reduce the possibilty of detonation. I am thinking a vortec head with 64 cc chamber.

Just tossing it out there.

Joe

Joe is right, use as small a chamber that you can and a true flat-top piston for max burn eff. here!!

Or again like he said, a small chamber AND a MATCHING chamber outline dish in the piston IF you are still at too high a CR. for pump gas use..

And I figure the older SB -461 and later 305HO, -601 doube-quench type heads help here too!!!!

And as a side note, I figure that this is where the BB stock heads have a problem b/c GM or as for that fact, nobody else make's an inexpensive closed chambered stock type large oval cast-iron head so that the 454 P/U motors with their stock flat-top pistons can make good CR!!! I'm talking 9.75 to almost 10 to 1 CR. here....

pdq67

PS., I wish W/P's would step up to the plate and make a stock valve train, cast-iron 90 cc closed chambered, 290 cc intake port large oval head and I bet they would sell a sh-t-pot full of them to guys with the old stock flat-top pistoned 454 P/U motors!!!

This would get these old motors up to like almost 10 to 1 CR if my numbers are on??

I have 8.49 DCR is that ok on pump gas?? Thats what i got for your setup too 8.49 but i didn't know your combustion chamber size so i just estimated. mine is 10.7 to one with almost the same specs as you but my intake closes at 66*. How many psi is 10.7:1?