Do not use that calc. There is no way to calculate slow lobes(or any lobe that is not using it's lobe acceration ramp it uses for it's calculation).

Use Pat Kelley DCR calculator. and try 75 abdc for your closing point

 

Ok thanks, using 75* gives me 7.38 DCR with stock compression, thats more like what I have found. I wish I could find the .006" #'s for the stock cam.

 

How do you know what degrees he should use for abdc?? Is that the factory cam spec?? 7.38 seems ridiculously low for anything other than a supercharger/blower (not turbo). But, I am not an expert.

 

Sounds like he's saying just pick any random value, I think...NOT! That value is very cam-specific...

 

I was thinking the same thing ...

 

I won't say this is the exact way, but here is how I did it. The piston rocks in the hole. Measure both sides at their max height. In my case is was .011 on one side and .013 on the other. Add them up. divide by two, then divide by two. so.. .011 + .013 = .024 / 2 (average height) = .012 divide that by two to get the height that of the piston when it's level. .06 for me. Now that I think about it. That last calculation might not work too perfectly. But, as I measured it when it was level, .006 did repeat itself.

Offset pin will give one side higher than the other.. One number should be smaller than the other.

It is also this rocking in the hole that made my decision to go .045 head gasket crush height instead of .040. I know others have done it just fine, but I guess I'm just not the huge risk taker I used to be.

Another way is to put a straight piece of steel across the piston. Lock in a dial gauge over it to zero while the piston is down in the hole. (deck height plus piece of metal..-- strong and straight) then spin the motor over and watch the dial caliper as the piston pops out and pushes the metal up (assuming LS style). Easier, but doesn't get you all the other measurements on furthest rocking height. Also be sure that the piece of metal is centered over the center of the piston pin. Otherwise it might be off a bit.

 

Who said it was random? But thanks for your confidence (must be my idiot check signature again). Here's more spoon feeding Duration was measured way back in the day at around 270/280 (you'll note that in close to a stock LS6 cam for base duration). With a 119 lsa/icl that puts it at 74.5 abdc or close to it. Problem with the factory cam is the production variance and year cam changes dcr very easy. Also the due to the production differences of that stock cam. You might have a dcr of 7.5 or 8.0 (in theory), way too much difference. Since the op thought he was at over 9 to 1, I gave him the best info I have seen over the years for a stock cam. I have seen measurements of less than 270 and way more than 270 on the intake depending on the cam and how it's measured. No easy answer. I remember when people used to say the DCR was 6.7 or so. I never believed those low numbers but they were using 300 base duration on a 119 icl. You could see that a 115.5 icl/lsa 2001 and above, would also boost DCR. With that 190-200 psi I always thought 8 to 1 seems more realistic. But running the numbers came up below 8.0 depending....

PAUL 57. Pat G might still have the spects off some old cams lying around. If I did not just slide in a new cam in my 427, I would throw in one of the stock cams again to check for you. But, like I said that would only be good for that stock cam. Before you make decisions about DCR and read to much into there importance, you might want to read this...

http://www.advancedinduction.com/LSX...BilletCams.php

I do use DCR as one of the criteria for a cam in a givin combo, SCR and environmentals + Ve of heads, ect. are just as or more important..