Question about compression

[Joker Z28]

LT1 383 stroker H/C/I (bottle fed every now and then)
with a 12.3 compression can you get away with pump 93 ocatane gas or is "race gas/high octane" required.

[TA the destroyer]

its really tough to say their are soo many variables involved. i would say yes but with a special tune and it will most likely run pretty rough. but youll also have to have a differnt tune when you want the full potentiol or see some track time. i think it depends on how good the tune is and hopfully it doesnt knock.
but thats just my 2 cents im sure someone has more experiance then i.
just too many differnt things invovled, whats done to the heads, what size cam and alot more to go on..........

[95formula383lt1]

ppl are doing it yes, i will be as well, but u need a dyno tune mail order wont cut it.

[Joker Z28]

Hmmm, you think a mail tune would be able to let it get around for a little while? There are no close dynos with good tuners around for miles and miles away.

I was talking to an old school "drag car" racer who builds and races cars all the time but he only works on carbed motors. I dont know if it makes a difference but he was saying with that high of a compression I wouldn't be able to go WOT without blowing it up and forget about even thinking about spray unless its on some sort of race gas like VP or c16

[Dangalla]

i would guess that you are pushing the limits, but...

i will tell you that there is no way to tell without the dynamic compression ratio - which is what octane requirement is actually a function of, not static - plus the rest of your build, and you will also need someone to calculate that for you, because i cant

as far as nitrous goes you would have to have a spot on n/a tune and pull timing with an ignition box - alot of it - if its even possible

[TA the destroyer]

Hmmm, you think a mail tune would be able to let it get around for a little while? There are no close dynos with good tuners around for miles and miles away.

I was talking to an old school "drag car" racer who builds and races cars all the time but he only works on carbed motors. I dont know if it makes a difference but he was saying with that high of a compression I wouldn't be able to go WOT without blowing it up and forget about even thinking about spray unless its on some sort of race gas like VP or c16
you will need a well experianced LT1 tunner , and you will also need to data log the car to get the tune spot on with a mail order. why do you wanna go soo high on pump gas anyway?

[Z28pr0jekt]

It depends on how much timing is in the motor. If you tell a mail order tuner to specifically set the timing low, then you should be fine for the time being.

[Dangalla]

It depends on how much timing is in the motor. If you tell a mail order tuner to specifically set the timing low, then you should be fine for the time being.

so without knowing his dynamic compression ratio, or any information about his build - your recommendation is that he will be fine, just pull some timing?

how exactly did you calculate his octane requirements?

i am just asking because every piece of information i have ever read states that he will be right on the borderline, and there is no way to know for sure without actually calculating it. at the point he is at his choice of cam will make the difference most likely

being that close i surely wouldn't just guess, and i would never recommend someone else does either

[Joker Z28]

Heres the thing, I talked to LE about my build he has my heads and intake. I am ordering the LE2 hes the one who said I should have a 12.3 comp. He never said anything to me about using race gas but I plan on running 93.
I am trying to get a hold of him but nothing yet.

[Dangalla]

i think there is some confusion there

http://www.camaroz28.com/calcs/crchange.html

using 500 flywheel hp, going from a stock ratio of 10.5 to 12.3 gains 20 hp, or 4 percent

sound worth it to you?

i would not go that high for a street car

[TA the destroyer]

i think there is some confusion there

http://www.camaroz28.com/calcs/crchange.html

using 500 flywheel hp, going from a stock ratio of 10.5 to 12.3 gains 20 hp, or 4 percent

sound worth it to you?

i would not go that high for a street car
and it just not the hp gain either, also ride qualitiy is effected as well as low end throttle response.
i agree thats too high for a street car. your walking on a very thin line.

[Joker Z28]

Ok but I do not have much choice in this, LE said the heads he is making for me will give me a comp at 12.3
At first I didn't think anything of it until now.
Also LE is not responding to my e-mails or phone calls.

[TA the destroyer]

well hes a really busey guy im sure he will get back to you. your best bet on this one is talk to a good tunner cause this is where your main concern is gonna lie. also their is a member on LS1LT1 by the name slowass93 i think. well he has a maroon 94 z running 12.5 comp ratio im pretty sure of. hes a regular member go their and he might be able to help you. i know he DDs his some time.

[Dangalla]

Ok but I do not have much choice in this, LE said the heads he is making for me will give me a comp at 12.3
At first I didn't think anything of it until now.
Also LE is not responding to my e-mails or phone calls.

thats not possible, its your choice of pistons that will raise compression that much, do not get me wrong milling the heads will raise compression but remember that he is also removing material from the combustiion chamber which will lower compression, and you could not mill a stock lt1 head enough to raise compression that much

be patient, he is very good about answering questions and getting back to customers, he will get back to you and explain everything i am sure

what pistons did you use or have you not ordered them yet, also keep in mind that your cam specs with dictate what your dynamic compression is and that is the important number when talking about octane requirements

[Joker Z28]

Ok they are LE2 heads with a custom grind cam of 236/244 .592 lift and a 114 LSA

I do not have a bottom end picked out yet I think I am going to go with Eagle/Scat rotating assembly but havent picked the exact 1 as of yet.