First: Im not planning on doing this as an 'exact science,' i just want to get within a ballpark range. Im in the process of a cam swap and i was told that my cam will react well to some extra pop. Ive been told that you can run as much as low 12s on 93 octane, depending on how good you can tune an engine. My car isnt a DD, and I am planning on tuning it myself so what do you guys think i should shoot for? Gas stations around here carry 94 octane and i usually run that but id like to be 93 compatible for when i cant find a sunoco.

Right now i was thinking mill maybe .025 and run an impala gasket. (I think this would be around 11.6:1?) could i go more than that?

Opinions? Also I am for sure going to mill them, just want to know how much i can do.

 

Uh, perhaps you might share the cam specs.

 

its an AI cam: 226/234 .540/.575 110LSA

 

I think what the other guy was trying to get at is figuring your DCR along with your SCR. Milling 0.025 on a stock block will put you at/close to zero deck. Impy gasket is good for a tight quench, but you might want to check P to V. I think you are fine with 11.6 any higher will be pushing it.

 

after 11.6.1, 11.8.1 your really starting to push your luck. The reverse cooling helps but than you run into issues of getting bad gas things could go south fast.
But there are guys who run 12+ so it all depends what your willing to deal with.

 

Im aiming for 12:1 will be more like 12.5:1 I figure wish me luck haha, if for some reason you can't tune yours, just go with a thicker gasket.

 

i would think 11.6:1 would be safe and reliable...

 

I have 12.2:1 on use 92 octane...no issues.

 

If that cam has enough overlap and with a 110 LSA, it might, you should be able to run 11.6 just fine and perhaps as much as 12:1 with a good program. 94 octane will certainly help. But why push it to the upper limits? Being conservative on a driver combo is wise.

 

its a weekend/pleasure vehicle. I dont rely on it for anything except that

 

it seems like you are already set on running a low 12 compression ratio and are looking for reason to do it as opposed to reasons not to do it... if you feel comfortable with a low 12 ratio then go for it but i wouldn't take the chance on messing up my toy... good luck with your choice and can you do me a favor and post up some results when you get it dyno tuned...

 

Chasing compession is pretty dumb unless the heads are off and need milled anyway for flatness. The gains are not worth the effort merely to have higher compression. We're talking 1-3% power increase here maybe. On a 500fwhp engine that would be 15fwhp. If your butt dyno can pick that up its alot more closely calibrated than mine.

Its also not necessary with that small cam either. You may see a marginally better idle and 5-10 more tq in the low/midrange, big deal. If the heads are off and getting ported and milled anyway by all means have it done if it makes you sleep good at night. Don't expect that to make it a world beater though.

 

no im not I just havent heard any good reason not to yet. Some say you can run it with no problems others just say thats "pushing my luck." I also hear people say its worth nothing in power gains and others say solid 10-15 rwhp. The people that designed my cam say that I will notice a difference with some extra compression. They have used this cam in several combos so id like to believe them. The guy i talked to that had this cam is running 11.6:1 with this cam and is making 365 rwhp... i cant argue with results like that with how many [mild] cam only cars i see in the 320-340 range.

 

OK here is another concern. Pushrod length. Am i going to have to run shorter pushrods taking that much off? If thats the case, i wont mill as much. Also now that i have the cylinder head off, it doesnt look like there is much room to mill at all before you would be hitting the valves... not quite what i had recalled from the last set of heads i worked on.

 

You take the valves out to mill. So they arent there, so long as you dont mill past the top cut on the valve job you should be fine. Alot of lt1 heads end up with valves proud of the deck surface when you get done milling them....

Pushrod length should always be verified with new rockers and camshafts as either can change the geometry, it should also be verified when milling heads or running thinner gaskets as well.

After you get done milling you may even have to do a little work so the intake will bolt back on properly.

While they're off at least have the clearances checked, and have them cleaned and a valve job done.

I already said if it were me I would leave well enough alone until I was ready to really go through the heads and have them ported. I think its a whole lot of brain damage for nothing much. But what do I know I only did engine r&d for 6 months last year for a major auto maker.

Good luck to you.