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VP C-12

Posted By: 440lebaron

VP C-12 - 07/25/22 08:38 PM

is to much octane to much?
400, stk 452 heads t/quad stock intake, headers, 4:56 gears 4100 lbs
Posted By: AndyF

Re: VP C-12 - 07/25/22 08:54 PM

Yes. Too much octane slows down the burn and makes the engine sluggish. It also burns a hole in your pocket.
Posted By: mgoblue9798

Re: VP C-12 - 07/25/22 09:30 PM

You need to optimize dynamic compression, valve timing events, and ignition timing for a certain octane level -plus a little margin for safety. Any fuel with octane rating exceeding what the build is designed for is just wasted money.

Posted By: FastmOp

Re: VP C-12 - 07/25/22 10:07 PM

Test
Test
Test ical
Posted By: 83hurstguy

Re: VP C-12 - 07/25/22 10:13 PM

Octane and the burn curve aren't necessarily related. High compression engines need higher octane and also typically operate at higher RPM ranges, which requires a faster burn...

You'll find that fuels have varying Reid vapor pressures that will help with intake charge cooling more than others, which may help increase power via better atomization/distribution. A lot of stock eliminator guys will typically run C11 or C12, and those engines have less than 10:1 compression and huge cams that produce low cranking compression. Some fuels like hot vs cool engines (or hot intake charges from boost).

That being said, many people use race fuel for consistency in tuning run to run (or class rules) even if the engine doesn't require it. I have a big block iron headed engine here with 10.5:1 compression that doesn't care whether it's on pump or C12 (it actually picked up a tick on pump on the dyno). My stock 440-6 has some preferences that show up on the dyno in terms of fuel, but it's maybe 5 hp difference.

Pump gas is inconsistent but also oxygenated, which can help make power. You may also find that race fuel has lower specific gravity than the pump gas you're running, which means you need to jet up to get the same power input.

Overall - fuel testing and tuning takes a lot of time and effort. It's definitely not as simple as the guy at the cruise night spouting off "yeah she really runs good with the race gas!"
Posted By: slantzilla

Re: VP C-12 - 07/25/22 10:13 PM

Is that the spec gas in Stock?
Posted By: fast68plymouth

Re: VP C-12 - 07/25/22 10:57 PM

In nhra stock, you have to run a fuel that’s on the approved list, and it will get checked after you make a pass most of the time.
Posted By: Cab_Burge

Re: VP C-12 - 07/26/22 01:19 AM

Originally Posted by fast68plymouth
In nhra stock, you have to run a fuel that’s on the approved list, and it will get checked after you make a pass most of the time.

how long ago did that start?
Posted By: slantzilla

Re: VP C-12 - 07/26/22 02:24 AM

8 years or so ago.
Posted By: SLO-KID

Re: VP C-12 - 07/26/22 03:21 AM

13.5-1 439 small block 7800 shift point been on C-12 since dyno day.
Posted By: 440lebaron

Re: VP C-12 - 07/26/22 11:18 AM

no fuel check yet, 8-1 compression
Posted By: rb446

Re: VP C-12 - 07/26/22 01:26 PM

That'll run good on 87 prob, back in the day running my 440-6@9.8:1 with single 850DP I ran what we called 4 star leaded fuel, approx 97 octane, decided to add unleaded to it, and boy it sounded so much stronger, didn't go much faster but.
Posted By: 440lebaron

Re: VP C-12 - 07/26/22 02:01 PM

YEP, no pump gas in stock, running in super street SST to break in car, illegal 383 still waiting for piston for 400
Posted By: fast68plymouth

Re: VP C-12 - 07/26/22 02:10 PM

“If it were me”, and I were running an 8:1 motor in Stock, I’d initially be using whatever was the least expensive legal fuel on the list.

After the car was sorted out and quite repeatable......... then you could experiment with some different fuels to see if there is a performance gain over the cheaper stuff.

Of course, I wouldn’t be messing around in S/St either.
Just put the 383 in the car, with the correct cam, heads, intake, carb and start making runs.
Swap the short block when the new 400 is ready.
Posted By: INTMD8

Re: VP C-12 - 07/26/22 02:17 PM

Originally Posted by 83hurstguy
Octane and the burn curve aren't necessarily related. High compression engines need higher octane and also typically operate at higher RPM ranges, which requires a faster burn...

You'll find that fuels have varying Reid vapor pressures that will help with intake charge cooling more than others, which may help increase power via better atomization/distribution. A lot of stock eliminator guys will typically run C11 or C12, and those engines have less than 10:1 compression and huge cams that produce low cranking compression. Some fuels like hot vs cool engines (or hot intake charges from boost).

That being said, many people use race fuel for consistency in tuning run to run (or class rules) even if the engine doesn't require it. I have a big block iron headed engine here with 10.5:1 compression that doesn't care whether it's on pump or C12 (it actually picked up a tick on pump on the dyno). My stock 440-6 has some preferences that show up on the dyno in terms of fuel, but it's maybe 5 hp difference.

Pump gas is inconsistent but also oxygenated, which can help make power. You may also find that race fuel has lower specific gravity than the pump gas you're running, which means you need to jet up to get the same power input.

Overall - fuel testing and tuning takes a lot of time and effort. It's definitely not as simple as the guy at the cruise night spouting off "yeah she really runs good with the race gas!"


Good post, agreed. thumbs
Posted By: Scully

Re: VP C-12 - 07/26/22 02:39 PM

Originally Posted by Cab_Burge
Originally Posted by fast68plymouth
In nhra stock, you have to run a fuel that’s on the approved list, and it will get checked after you make a pass most of the time.

how long ago did that start?
More than 30 years ago.
Posted By: Cab_Burge

Re: VP C-12 - 07/26/22 08:38 PM

The last time my old M.W. race car ran in NHRA stock was in 1988, it ran better on VP C12 at that race than it had with the SO CA local race gas Daeco brand boogie
NHRA would check the polarity on gas in both SS and Stock but not in any of the Super heads-up classes back then shruggy
Both of those classes can be tough to do well in scope
good luck on your efforts up wrench grin
Posted By: PJ68RT

Re: VP C-12 - 07/26/22 09:52 PM

Engine masters octane testing

https://www.youtube.com/watch?v=ryqyTPfNj1Q
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