bronko91

iTrader: (4)

So I am yanking the heads off again so I can enlongate the pushrod hole for my new shaft mount adjustable rockers. Engine is a 408 iron block LS1, heads are P&P Dart 225.

Question o' the day is how much does CR affect HP? I know static CR is affect by the cam which is a custom one off from Thunder Racing (232/238 .613/.601 111LSA) with some milder lobes. I got tired of needed 921 springs to control some pretty harsh ramps. So I went to a milder ramp so I could put some milder springs in (Crane Duals).

I found a way better CR calculator and I thought I was over 11:1 but it now appears I am closer to 10.7:1. Should I sweat it?

Here are the car details, well most of them anyway:
http://www.cardomain.com/ride/2227913

jg04222

dynamic compression ratio is affected by the cam. i would say that you'll probably be ok with the CR and cam you have; it doesn't have a ton of duration. remember, just jacking static CR up does not yield much more performance, it just makes you have to run really high octane fuel (or alcohol). it is just one component necessary to fully utilize the power potential of a larger cam.

bronko91

iTrader: (4)

well, my cardomain page has 11.5 which is what I thought I was at, trusting one of our club sponsors (name withheld out of courtesy) who did my heads. I found a very extensive CR calculator and it put me at 10.7, this is with a head gasket thickness of .073. I think I need to be about .065 which will raise it to 11.4. The engine has just been started and idled and I am being told the cometics will handle being taken off and reused since I have not really run the engine yet. So this is coming down to a cost vs performance gain. Do I stay at 10.7 or raise it back up to 11.5? I will still be running 93 octane and can tune the car for that. How much HP am I going to gain going from 10.7 to 11.5? The car domain page has not been updated to reflect the 92mm TB / manifold nor the 100mm MAF and 4" hardcore. Have not dynoed this setup yet but will cry if it is under 500.