i got a used engine, used heads and used cam

did my homework, but just want to confirm my findings because i dont do these calculations very often. I'm about to send my carb off for a rebuild, and i need to know if i should have it converted to e85 due to my compression and DCR. anyways, here is the combo, and if you have any questions i can answer them.

Engine:
stock bottom LS2
Stock head gasket
61 cc combustion chambers (tfs 225 heads)

i figure after flycutting the intake side of the piston, i'm around 11.7:1 compression.

cam:


my calculations came out to 8.95ish DCR which is well over the "limit" of 93 octane according to internet racers who claim 8.7 or so is the limit.

can someone check my math? SC and DCR...once someone confirms my math, my next question is should i step up to e85 on this build. i plan to run a 200-250 shot through this engine too.

 

On my old 4.8 i had a dcr in the 8.5-8.6 range and that bitch could run on 89. Not very well but it did not ping.

Borrow my extra meth kit and let it eat. Just trigger it with a WOT switch.

 

I don't remember how many valve relief cc's a stock LS2 pistons has, I used 2cc for my calculations and 3cc after flycutting. Static CR is a little under 11.5 using GM gaskets and average deck height. I didn't calculate dynamic CR, but it's probably close to 8.8 which is close to your goal. If stock pistons are -3cc, you'll probably be okay.

EDIT: Nevermind, if the pistons have no relief (like TXsilverado says), then you are probably correct about the 11.7 static CR. I have a LS1 and knew they were true flattops (I've had the heads off a couple of times). For some reason I thought the LS2 had valve reliefs.

 

ls2 pistons are flat top with zero relief. i had to cut .090 off of the intake side using a 2.055 cut. the intake valve angle on a trick-flow heads is 13.5*.

 

this is annoying. i punch it into 1 calculator and see around 11.7:1 compression...into another calculator i get 11.57.

so i punch in the OEM specs of an ls2 and dont get 10.9:1 that it should spit out. dammit lol

 

the newest calculator (that shows higher than stock ls2 compression) that i'm using has me thinking my compression isnt as high as i originally thought.

at this point, **** it. i'm running 93 pump and will splash some race gas in when i'm on the nitrous. if it blows, it blows.

 

Does your nitrous have a standalone fuel system?

 

it will. havent got that far yet. need to get it on the track n/a and fix whatever bugs come up first.

 

Is it gonna make the ls1truck shootout?

 

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