Can anyone use one of their programs to find out the DCR of my combo?

I have a 327 bored .030" over and I am using a XS274S camshaft with a 10.3 compression ratio?

The camshaft is 106 ICL and 110 lobe separation. It has a 63 degree intake closing and is calculated at .015" tappet lift.

Can anyone come up with the DCR I would get with it. I have used Pat Kelleys DCR and it comes up with 10.3 compression ratio and 8.2 : 1 DCR does anyone get a different DCR with any of the other programs that are out there.

I will have a o decked block and a .039" head gasket with edelbrock performer RPM heads.

Can anyone help me out?

Thanks.

Here's another link. It uses .050 numbers and predicts cylinder pressure too. The DCR number is fairly useless from this calculator (because it uses .050 numbers and is quite a bit higher) but the cranking pressure is very helpful IMO.

http://www.rbracing-rsr.com/comprAdvHD.htm

Here's what it said about your combo:

Camshaft, Rod Length, Boost and Altitude Correction to Compression

Your engine summary is as follows: Bore 4.030 inches, stroke 3.25 inches, rod c-c length 5.7 inches, with a static compression ratio of 10.3 :1. Your camshaft specifications call for an inlet valve closing of 44 degrees ABDC (after bottom dead center).

Your chamber volume is 73.05 cc's. With this camshaft your dynamic, or effective stroke is 2.91 inches. Your dynamic compression ratio is 9.33 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 193.77 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 0 PSI is 9.33 :1.

Knowledge is power.

PS. In your case 193 psi is fine for an aluminum head engine with proper quench.

Imho, just input the advertised spec's into the rbracing link calculator and see what you get?

Eff/dynamic CR. calculators are based on math that finds the stroke at the time of intake valve closing is why .050" numbers are worthless. B/c at .050" timing values the valves aren't closed!

I figure both Pat's and the Boost Calculator link SHOULD spit out about the same numbers if the inputs are the same!

pdq67

Eric68,

How do you get 44 degrees ABDC at .050" lift? I would just like to know how to get that 44 degrees? IF you are getting 9.33:1 dcr that would be very high. IF I am reading that right? It is a little complicated to me but I am slowly figuring it out.

Thanks for your guys help.

How do you get 44 degrees ABDC at .050" lift?

106 degree lobe center plus half the .050" duration equals 224 degrees, which is 44 ABDC.

Your cam specs show .050" lift occuring at 44* ABDC when the intake is closing. All you have to do is plug your .050 duration numbers, LSA and ICL into any of the cam timing calculators.

Eric68,

I was just wondering where you got the cam spec card from. I went on CompCams website but I can not find anywhere that it gives me 44 degrees ABDC at .050". Could you let me know where you found those specs.

Thanks.

I got the specs from the Comp catalog, then plugged them into Pat Kelley's DCR calculator (the middle tab that calculates timing events)