Octane

MACH1MUSTANG · Jan 29, 2007

Is it worth running a 50/50 mix of 110 octane race gas and 93 octane pump gas in a built up 1969 351W? When I got the car it would ping on only 93 during WOT but with this mix, no ping and I can basically put as much timing in it as I want to. I have a stock dizzy but pulled the points and I'm running a Pertonix set up. It also has a holley 750 carb. Is this fuel mixture safe and what is the optimum timing set up initial and total? I can or can not use vac adv., doesn't matter to me since I am not looking for fuel milage, I'm looking for HP.

66Runt · Jan 29, 2007

that is a very vague question

.

MACH1MUSTANG · Jan 29, 2007

1969 351W, bored .030 over, file fit 11:1 compression pistons, mild cam, solid lifters, 3 angle valve job, headers, edelbrock performer intake, 750 Holley best describes the engine.

ratio411 · Jan 29, 2007

11:1
Performer intake
750 Holley
Small cam

Sounds a little mismatched IMO.
The compression and carb go together, then a small cam (without knowing specs) and such a VERY mild intake go together.
The problem is that small cams and intakes can magnify the ill effects of high compression, as opposed to complimenting each other.

GNN60GT500 · Jan 29, 2007

In the meantime no pinging with too much octane is better then pinging with not enough-

ForceFed70 · Jan 29, 2007

GNN60GT500 said:
In the meantime no pinging with too much octane is better then pinging with not enough-

Definately run the higher octane fuel until the pining is sorted out.

It may be that taking 3* out of the timing will stop the pinging and result in MORE horsepower than running the higher octane fuel with more timing. Although with 11:1 and stock iron heads, he might be stuck with race gas no matter what the timing is.

D.Hearne · Jan 29, 2007

I don't agree, with the right cam 11 to 1 and iron heads is very possible. My 68 Merc's 390 was fine with stock iron heads (C8AE-H, good quench heads as are the 69 Windsors) and 89 octane gas. Just what is this "small cam" anyway? Pinging could also be the result of too hot plugs and a too lean fuel mixture. And too much timing can do damage too, even with the right octane, you're basically putting more stress on the rods, pistons and bearings trying to compress the fuel mixture that's starting to ignite. Try running straight 93 again, but pull off the timing till it stops the pinging, then get back to us on what that is.

ForceFed70 · Jan 29, 2007

Who don't you agree with? I personally said he might be stuck with race gas. I know it's possible to run 93 octane with iron heads and 11:1 but at this point it can go either way.

ForceFed70 · Jan 29, 2007

Dbl post.

ratio411 · Jan 29, 2007

D.Hearne said:
I don't agree, with the right cam 11 to 1 and iron heads is very possible.

That is kinda what I was getting at.
Usually mild cams build cylinder pressure which in turn magnifies the effects of high compression and in the end, hurting performance.
You can run high compression and iron heads with great results if your cam has the right overlap to bleed off some pressure.
Mild cams are often even specifically designed to boost cylinder pressure.
If you mix one of these cams engineered as such with high compression, there is almost nothing you can do to stop ping short of changing one or the other component.
Or run diesel fuel...

D.Hearne · Jan 29, 2007

If he's got the cam I think he does ( go look at his cam specs thread) he'll probably need to do a cam swap or retard the crap out of it. Depends on how accurate he is with the comp ratio.

D.Hearne · Jan 29, 2007

BottleFed70 said:
Who don't you agree with? I personally said he might be stuck with race gas. I know it's possible to run 93 octane with iron heads and 11:1 but at this point it can go either way.

Don't get your blood pressure up, I wasn't picking a fight here. OK, so you said MIGHT

ratio411 · Jan 29, 2007

I ran your cam numbers and I come up with almost 17" of vacuum at idle.
Should run very smooth.

ForceFed70 · Jan 29, 2007

D.Hearne said:
Don't get your blood pressure up, I wasn't picking a fight here. OK, so you said MIGHT

Lol, did I come across as angry? I didn't mean to.

D.Hearne · Jan 29, 2007

BottleFed70 said:
Lol, did I come across as angry? I didn't mean to.

I don't know, I thought I might have stepped in it there for a second.

or maybe you were gettin Cabin Fever up there in the frozen north.

Octane

MACH1MUSTANG

New Member

66Runt

Member

MACH1MUSTANG

New Member

ratio411

GNN60GT500

ForceFed70

That's why they call it "dope"

D.Hearne

New Member

ForceFed70

That's why they call it "dope"

ForceFed70

That's why they call it "dope"

ratio411

D.Hearne

New Member

D.Hearne

New Member

ratio411

ForceFed70

That's why they call it "dope"

D.Hearne

New Member

Similar threads

Octane

New Member

Member

New Member

That's why they call it "dope"

New Member

That's why they call it "dope"

That's why they call it "dope"

New Member

New Member

That's why they call it "dope"

New Member

Similar threads

Privacy & Transparency

Privacy & Transparency