What Octane do you need for a 427

[Ricochett]

What Octane do i have to run with a 427 motor .030
Compression is 12:1 will pump gas work like 93 octane????
Thanxs for any help it is a brand new motor i started it up with
Cam 2 fuel right now just trying to see how much is really needed!???????

 

[XLR8]

Ttt

That's a good question and these are definitely the right folks to ask. Sorry I can't answer it but I can give your thread a bump to keep it on top of the heap.

Jane Ann

 

[bill81vette]

I don't see any reason not to use 93 octane.
but I suppose if you want to run Cam2 that would be your decision,and your $$$$.
its pretty much a personal decision and vette!!!!

 

[GS Diva]

We always used 93 octane for our 2008 Z06, and we continue to do so with the Callaway.

Elaine

 

[Tuna]

I assume that you asking about a Big Block 427 without electronic engine controls and a carb rather than the current LS7 Small Block 427?

Depends on whether it's pinging or not and whether you want to reduce the overall timing any more. With 12:1 compression, I'd be using a fuel with 100 or more octane.

 

[catbert]

Tuna hit it on the head. The specs for the 427 make the constant tweaking of engine tuning by the computer controls almost mandatory. Using the non processor systems mean tuning for the worse case scenario, and conservative timing, etc. With the high compression of the 427, computer controls make life easier.

I remember a time when I was stuck in the middle of New Mexico with no premium fuel available, and my C6 Z06 ran fine on the local mid-grade, which was 90 octane. That's amazing.

 

[6880 Mike]

...Compression is 12:1 will pump gas work like 93 octane?...

Yes, but it won't like it.

 

[Hib Halverson]

You can't run 93-oct. gas in a 427 with 12.5:1 compression without detonation unless...

1) You never run the engine hard, ie: nothing over half throttle and no high rpm operation
2) You recurve the spark advance to retard timing and you make the WOT air/fuel ratio slightly rich.
3) Understand that retarding spark will make the engine run hotter.

While the above three are practical solutions, they are undesirable compromises, In my opinion.

Better choices are..

1) Change pistons to reduce the compression ratio to about 10:1 (iron heads) or 10.5:1 (aluminum heads)
or
2) Run a mix of 93-oct. pump gas and 100-oct unleaded racing gas. The mix should be somewhere around 1:2 or 1:3 pump 93 to racing 100.

With either of those you can run the engine hard with optimal spark and fuel calibrations.

 

[JohnZ]

I'm with Hib - there's no way on earth a carbureted 427 big-block with 12:1 compression is going to run on 93 octane premium; unless you enjoy paying $7.00 a gallon for race fuel, it's time to change pistons.

 

[Ricochett]

I'm with Hib - there's no way on earth a carbureted 427 big-block with 12:1 compression is going to run on 93 octane premium; unless you enjoy paying $7.00 a gallon for race fuel, it's time to change pistons.

Thanxs everyone for ya'lls input i think i am just going to try to try and error
i mixed 1 gallon of 93 octane with 4 gallon of Cam 2 it seem to be okay now i just bought some more i used 2 gallon of 93 octane to 3 gallons of Cam 2 i think that is about the best or the safest ratio

 

[TimAT]

Yes, but it won't like it.

You Sir, have a tremendous capacity for understatement!!

I'm running 12.5:1 compression. I'm also running either VP110 or 100LL avgas. I back the timing up a little for the avgas, simply because I can't hear it if I start getting detonation. Prices being what they are, the avgas is just a bit cheaper.

 

[catbert]

I talked to a guy at a car show with a 427 BB who replaced his carb with a TBI and electronic controller, Holley, I think. He said it was easy, and now he has a daily driver that isn't fussy about what 93 octane he uses. He said it is easily reversible. He even made a stock air cleaner work.

 

[vetteboy86]

Thanxs everyone for ya'lls input i think i am just going to try to try and error
i mixed 1 gallon of 93 octane with 4 gallon of Cam 2 it seem to be okay now i just bought some more i used 2 gallon of 93 octane to 3 gallons of Cam 2 i think that is about the best or the safest ratio

After your trial you could always pull the plugs and see how they look. See if there are any signs of detonation.