Well I think running around with stock injectors has taken it's toll, and the heads are coming off and I am thinking of going in a different direction with my car and staying with an NA build.

So I am going to be doing some additional upgrades to the heads since I am pulling them anyway(and yes larger injectors 42lbs) and have a question. I am going to tune for 93 octane and the heads/intake are going to be milled. Now I have been playing with my compression calculator (with cylinder head CC and gasket thickness) and the where I am at is a pretty good point it looks like to go in what appears to be safe or outside. But I have incunclusive info on this site, and others.

Depending on what headsgasket I run, my DCR will be anywhere from 8.964 to 9.417 on the highside. Assuming the tune is spot on, is 9.417 too much to run 93 octane? If so, what do you guys think I should be aiming for? I have seen 9.0 stated on here as the max, but at the same time seen people with over 13:1 SCR still run 93 and there dynamic I would guess is probably over 9...

Thanks for the feedback,

Josh

 

i doubt anyone is running pump gas with 13:1 static. my compression ratio is 12.3 but i have quite a large cam to compensate so it can run on pump gas.

 

I have seen on here atleast one person claim to be 13:1 static and running 93 octane with no problems. That's why I am sking for opinions, so that I can make an educated descicion on what I should(n't) do

 

9.4 DCR should be fine for pump 93. I would be worried if you start getting closer to 10, but in the lower-mid 9's should be fine with the reverse flow cooling....just make sure the tune is spot on, otherwise you will break something.

 

Think about this for just a second. If you have 13:1 static compression and lets say with your cam sitting where the intake valve closes 40ABDC you have 9:1 DCR. Now if you retard the cam 40 degrees you will have 13:1 DCR but you might be running on race gas, does that mean that the engine will like a cam that is running 40 degrees retarded? I kinda doubt it. Don't worry about DCR. Look at the combination and use some basic common sense.

BTW, if you were stuck on looking at some DCR number, I wouldn't run more than 9:1 on 'pump gas' unless everything was right

 

I am not stuck on anything, nore have I made my mind up on the choices I have. The reason I posted up DCR #'s is because anytime someone asks, " What is your opinion on octane" and doesn't they get blasted for not looking at the whole picture.

So I used my compression calculator program and calculated different options for both DCR and SCR just changing the head gasket thickness. I agree that common sense plays more a factor than most will want to admit. But sense I am approaching an area that I do not feel I know enough about, I am hoping to learn and make a choice that will work for me.

Thanks for everyone's feedback so far.

 

I have built 2 LT1 engines with high DCR. One was 9.2 and the current one is 9.4. The have SCR's of 11.2 and 12.2 respectively and have no KR and run fine on 91 octane. Further, the current engine, I race the crap out of it (road racing) and have had the heads off recently with no sign of predenotation.

Ben

 

That is good info and comparrison, thank you. Did you take the heads off just to check everything out or was there an issue, if you don't mind me asking?

 

What an insulting question! God people don't know common courtesy!

Of course I don't mind you asking. I took them off because I had a coolant leak I could never find and thought it was the gaskets. New gaskets and still leaks but I fixed it. I run gasket sealer permanently in my water mix. No more leaks!

 

lol, sounds like my humor.