Yellow Bullet Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
1,815 Posts
Discussion Starter #1
11.3:1 compression, heavy car, 351C with factory closed chambered iron heads, flat tops. Wondering what is a good mix I can run and not worry about detonating to death. My choices in this area aren't real good (PA), and no E85 but there might be E15. The pump gas is up to 93 octane but they put up to10% alcohol ( I think) in the mix. So far I've been running VP110, but I'll need to start running some form of pump gas eventually. What about octane boost additives? Also, there are a couple stations that offer 91 octane "straight" gas (no alcohol). Do the alcohol mixes need richer jetting? Thanks
 

·
Registered
Joined
·
277 Posts
11.3:1 compression, heavy car, 351C with factory closed chambered iron heads, flat tops. Wondering what is a good mix I can run and not worry about detonating to death. My choices in this area aren't real good (PA), and no E85 but there might be E15. The pump gas is up to 93 octane but they put up to10% alcohol ( I think) in the mix. So far I've been running VP110, but I'll need to start running some form of pump gas eventually. What about octane boost additives? Also, there are a couple stations that offer 91 octane "straight" gas (no alcohol). Do the alcohol mixes need richer jetting? Thanks
We have a somewhat heavy bracket Camaro 11.5:1 434 sbc. We just started running 91 octane UL/pump gas with Race Gas Concentrate. We mix it around 4-6 oz. per gal. Right around 99 to 101 octane after mixed. The 2 races I've used it, went to the semis & won the other one. The important thing to remember is it needs MMT in the ingredients. I named one, a couple others are Boostane & Torco Accelerator.
 

·
Registered
Joined
·
755 Posts
Torco Accelerator concentrate is the one I've used, makes up to 107 octane out of 93 pump @ 6.4 oz/gal ratio(64 oz in 10 gallons)

Price is a good bit better than the Race Gas Concentrate stuff...
Torco $23/32 oz,
Race Gas $36/32 oz

With the Torco, since you only need about 96 octane to run what you have 1/2 a quart can to 9 gallons pump 93 should do you up.
 

·
Registered
Joined
·
1,815 Posts
Discussion Starter #6 (Edited)
Have you actually had it detonate on pump fuel?
No. New motor so I haven't had the opportunity. With that said I remember years ago I had a fresh motor with similar compression, took it on it's maiden voyage during break in and when I dipped in the throttle it sounded like teeth being ripped off a nylon sprocket lol. It didn't hurt the motor, but it did "pepper" the piston underneath the exhaust valve. WIth that said I've detonated motors before with disastrous results and don't want to go there again...lessons learned, as they say.

Do you think I'll be okay with the gas straight out of the pump?
 

·
Registered
Joined
·
925 Posts
I ran 94 octane with 12.7:1 on 408 cleveland with quench chambers but aluminum A3'S. Not saying it didn't detonate without me knowing but ran for over ten years. Tight quench, tight P to V, lots of overlap, 31° timing but quicker piston speed than you if you are still 3.5" stroke.
 

·
Registered
Joined
·
2,113 Posts
With that compression on an old iron head engine, I wouldn't.

No saying that it can't be done with the right cam, maybe some chamber mods, and a good tune.

Between 91 octane non-ethanol and 93 octane E-10, non-ethanol all day. That is, with a good octane booster like Torco, VP Octainum, Race-Gas, or similar MMT based additive. I use the VP because Autozone carries it, and I stock up when it's on sale.
 

·
Registered
Joined
·
1,856 Posts
Where at in PA? We got alot of e85 around western pa Pittsburgh area
 

·
Registered
Joined
·
4,904 Posts
Arco 91 octane, Shit works with a gallon of race gas per 10 gallons 91. Under 11 to 1 compression.
 

·
Registered
Joined
·
1,363 Posts
No. New motor so I haven't had the opportunity. With that said I remember years ago I had a fresh motor with similar compression, took it on it's maiden voyage during break in and when I dipped in the throttle it sounded like teeth being ripped off a nylon sprocket lol. It didn't hurt the motor, but it did "pepper" the piston underneath the exhaust valve. WIth that said I've detonated motors before with disastrous results and don't want to go there again...lessons learned, as they say.

Do you think I'll be okay with the gas straight out of the pump?
I cant say, I have no expierience with iron headed stuff, I was just curious because all of my combinations in the last 12 years have been pump gas, starting at 10.75:1 static, to now 13.2:1 static and I have only had one time where I saw any kind of detonation, which just turned out being some bad gas, and it didnt hurt anything, but i have always had aluminum heads with "mild" camshafts.

There is a lot to it though. Static compression doesnt mean much in terms of cylinder pressure, I feel like the cam choice has more to do with it. Also, I have been running holley EFI since 2013 and I have COP, and the ability to precisely control fuel and spark, which I think really helps, and my new cylinder heads have a really efficient chamber and dont need a ton of timing to make power.
 
1 - 12 of 12 Posts
Top