I'm trying to calulate the DCR for 2 different cams and I think I'm doing it all wrong because I'm coming up with a 9.4:1 DCR.

The 2 different cam setups I'm trying to compare both use the same factory stock LS6 346cid longblock with the stock bore of 3.89 and stock stroke of 3.622, 10.5:1 SCR, the heads are stock 64cc ls6 heads and have stock 2.00/1.55 valves and use the factory .054 GM MLS headgasket.

I was trying to calculate the DCR difference between these two cams, 237/242 .603/.608 114LSA cam (110 ICL) and a 234/238 .598/.598 111LSA cam (109ICL).

 

I am on my work PC, but I have a calculator I found online on my home one, or id post it. Try to google one. Even then those arnt super accurate. Maybe call Scoggin Dickey or LME, A good builder and ask them to help you. with what you have there is NO way its 9.4. More like 8.4.

I racked my brain getting mine to where I wanted.

 

What is the spec for the Inlet Valve? What is the ABDC spec more specifically?

 

Using Comp Cams as a guide #54-446-11 232 @ .050" 71 degree ABDC I get 7.95:1

 

You need the seat to seat timing, not the .050 timing.... thats why your numbers are skewed.

Take the advertised duration, subtract the .050 duration from it and divide that in half.

That's the number to add to the intake valve ABDC timing to get the actual seat close timing.

 

I think rod length, and altitude will have an affect as well.

Just curious, what is the consensus about what is optimal for DCR?

 

Ok, I think I'm about spot on with my calculations for the 234/238 cam (ICV 46 and 14*overlap). I came up with a 10.6 SCR and a 8.1 DCR...

I'm still trying to calculate for the 237/242 cam.

 

Back when I did all this to select my first cam, the ideal was thought to be as close to 8.5:1 as possible.

 

Post both the advertised and .050 duration #s for each cam... as well as the intake centerline and the IVC (.050) ABDC I'll double check it for you.

 

237/242 .603/.608 114LSA - Adv duration is 286/291 and ICV is 49.5 ICL is 111*
234/238 .598/.605 111LSA - Adv duration is 238/287 and ICV is 46 & ICL is 109*

 

Your IVC seat timing is 74 ABDC and your DCR is 7.81 with that cam, installed straight up.

Retard it 2 degrees and DCR drops to 7.67
Advance it 2 degrees and DCR increases to 7.96

 

lemme google that for ya. http://www.google.com/search?aq=f&so...tio+calculator

http://www.wallaceracing.com/dynamic-cr.php

 

Thanks!