104 octane for my 360 ?

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pilotsf

pilotsf

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So I'm back again for some needed advice . You Have not let me down.
Im racing this Sunday at a bracket event. I have a medium built 360, 9:5 -1 comp, tuned 850 carb , comp cam timing at around 34 degrees runs a little lean under 2,000 rpm but awesome at W.O.T. my best time on pump gas was 13.50 at 102 mph. should I get the vp 104 and time my car at 36 or run it as is ? (I Just got some slicks to if I can run them(SportsmanRules). I was told if I run the 104 and don't advance my timing it will run slower. What do you guys think.
Thanks for all the help
Dale

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Unless you are running boost, the best power should be made with the lowest octane possible. Higher octane slows and cools the burn and in cases where the engine doesn't need it, and it's well tuned, race gas is a waste of money. You have fairly low static ratio (in the 9s) and iron big chamber heads. The only time I noticed a change was when I used C16 (all I could get my hands on) in a jetted lean N/A 440 that needed to run C12. It picked up 2mph just from the fuel...lol.
 
Agree with Moper on this one. The higher octane rating means that more heat is needed to ignite the mixture. If you're not having detonation/pre-ignition issues with pump gas, stay away from the high octane stuff. You'll only be paying more to run slower.
 
Does it ping with more timing????
I remember talking to you before but i don't remember what cam you have.
How big is the cams duration @ 50 thousands lift, and have you done a compression test to see how moch cylinder pressure you have.

Knowing how much cylinder pressure you have is the key for what fuel to use.
What is the timing is set at, and does it ping under load for that setting on pump gas. (wot)
 
T67POWER said:
Does it ping with more timing????
I remember talking to you before but i don't remember what cam you have.
How big is the cams duration @ 50 thousands lift, and have you done a compression test to see how moch cylinder pressure you have.

Knowing how much cylinder pressure you have is the key for what fuel to use.
What is the timing is set at, and does it ping under load for that setting on pump gas. (wot)
Click to expand...

IMHO at 9.5 you shouldn't need any more octane than 91 actually we run ours on 87......I would start at 30* and keep advancing until you stop gaining et. 8)

Rickster
 
T67POWER said:
Does it ping with more timing????
I remember talking to you before but i don't remember what cam you have.
How big is the cams duration @ 50 thousands lift, and have you done a compression test to see how moch cylinder pressure you have.

Knowing how much cylinder pressure you have is the key for what fuel to use.
What is the timing is set at, and does it ping under load for that setting on pump gas. (wot)
Click to expand...

Yep I remember you. Thanks for all the info. It does ping a little under load part throttle not much for 2-3 seconds. At WOT it runs great. I had the car tuned after our last thread. The timing is about 34 degrees right now. It runs awesome. The tuner said maybe try 104(vp) and go to 36-38 degrees at the track, but it ran great on the dyno 275hp 302 trq. the cam is480 lift duration .50. I'm running 76 91 octane gas. When I ran Sunoco 100 it ran a little better ( or it was in my head).
Thanks your help. again
dale
 
There is nothing better then going to the track and trying to make the car go faster your main goal.
At this point you have done a lot to improve your cars speed and et.
Every car is not the same and some rules can be broken.
If your car is pinging then its telling you something.
From what i read, you have this problem only at very low rpms.
This is the highest amount of load due too the rpm being so low and the fuel burn rate being to fast.
The motor is only lean because, as you know ,your only on the front two barrels.
You have this engine tuned in to the leanest setting possible at WOT POWER.
NOW ....
If you advance the timing just a little and add 104 it might stop the pinging but how much more power will you have if any??????
Look at your mph and see if it goes up.


Let me put all this an other way.
The weather is a big factor in performance and it's something most people forget about SO...................
Go to the track and make a pass, with the old set up first, and then make one change at a time.
I think the fuel will help you if you advance the timing.
I have a question concerning your carb.
What jets are you running front and back and what size pump shots are you using????
Sometimes increasing the pump shot size will stop a car from pinging at a low rpm because of the extra fuel making it rich at first.
I run large discharge nozzles (pump shots) in my cars and they hit nice and hard out of the hole.

SOME GREAT ADVICE >>> IF YOUR RACING IN A BRACKET EVENT, DON'T CHANGE ANYTHING.8)

IF YOU WANT TO FILL YOUR TANK AND ADD A FEW GALLONS OFF RACE FUEL THAT'S FINE, BUT,YOU WILL NEED ENOUGH FUEL WITH THE SAME RATIO TO FINNISH THE EVENT AND THAT MEANS A FULL TANK (MORE WEIGHT)
IF YOU DO USE THE RACE GAS, JUST WEIGH YOUR CAR AFTER YOUR FIRST TIME TRIAL SO YOU CAN DO THE MATH AFTER THE RACE TO SEE HOW MUCH OF A GAIN IF ANY YOU GAVE YOUR CAR.
Every gallon of gas weighs about 6 pounds.
This is if you remember how much fuel you had in it for the 13.50 run.
Oh yea ,The weather on that day too and blah blah blah :angry7:
GOOD LUCK AND CUT A GOOD LIGHT:cya:
 
Thanks ! I'm going to run it as is. check my timing , and I had about 2-3 gallons of gas on my 13.50 run. the slicks with smaller diameter will help me to. I hope i can use them without a drive shaft loop
thanks again !
 
With 9.5 to 1 compression you DON'T need 104 octane,you'll just be wasting your money..my 360 at 10.7 to1 compression runs 11's with only 93 octane at 36 degrees of timing..
 
Check out the hot rod magazine test on fuel.
It's not always the octane according to the test done by hot rod magazine. Race gas burns a little different and can possible help a motor just plain make more power.

I agree with stroked 340 that it is a wast of money most of the time,but in his situation, and if he is correct about the motor pinging, then it could let him tune the engines timing in with out any problems.

I was wondering what the size of the cam was @ 50 to get an idea about the duration and his cylinder pressure.
The lift is .480 but what is the duration @ 50?????
 
T67POWER said:
Check out the hot rod magazine test on fuel.
It's not always the octane according to the test done by hot rod magazine. Race gas burns a little different and can possible help a motor just plain make more power.

I agree with stroked 340 that it is a wast of money most of the time,but in his situation, and if he is correct about the motor pinging, then it could let him tune the engines timing in with out any problems.

I was wondering what the size of the cam was @ 50 to get an idea about the duration and his cylinder pressure.
The lift is .480 but what is the duration @ 50?????
Click to expand...

Yep @.50 . My pinging problem has been a HEAD MELT form day one. always pings at low rpm and load then runs great. I'm at 15,000 miles on the motor and every gear head I take the car to says its so minimal don't worry about it. My timing light is really touchy too. Its a dial light but from 32-36 it hardly changes reading. I might get some 100 octane and do a test and set it to 36.
So per your advice I will run it as is since the tune was done for the race sunday and after I will start backing down around 20 degrees and see if i can get the ping out.
One major note . The speed shop wants to put edelbrock rpm heads on it and give me about 30 hp to the wheels bringing me 310 hp 320 trq but that's a whole different thread.
 
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