[littleknife]

do we use racing gas mixed with unleaded or do we use a fuel booster?

 

[DanielC]

Move to Colorado.

 

[1971BB427]

High compression alone wont be an unleaded/leaded issue. It's a octane level issue. If you want to add race gas, or any high octane gas to your engine to make it run well and not have detonation problems it wont hurt whatever gas you run with it.
You will need to know what your heads are, and whether they have SS valves and hardened seats. If they don't then running any unleaded fuel will eventually ruin the valves and seats.

 

[327NUT]

What is your compression ratio?

 

[67Mustang Al.]

I run a 347 on pump gas which here is about 93 octane. At first it pinged (too much advance initial, and total. I have a choice of using 93 or 98 or de-tune my engine. I opted to detune and reduce initial timing by 4 degrees from 12 to 8 and reducing the total timing back to 28. I also changed the advance curve on the MSD to allow less advance at 2000 rpm. I would have lost power for sure but i dont drag race. The engine has 10.5 compression , probe pistons, performer rpm heads, stainless valves etc.
It does not ping now and has enough torque for my needs.Even under w o t it still pulls hard without any pinging.
AS previously said by "427" its your ocatane rating that counts.
Al.

 

[timothale]

Boat gas ?

I ve seen Boat gas sold along the Colorado river in Arizona , I'v see water injection kits , My nephew used one, he said it helped.

 

[littleknife]

reply to high compression with double hump heads 11-1 comp.

thanks for the replies forgot to say double hump heads with 11-1 compression. i have to have the heads checked out to see if when it was rebuilt they put hardened seats and and valvels. the guys i bought the truck and engine from raced super mods. flat track. so i am sure they used racing fuel! This engine is in a chopped and chaneled what used to be a 38 ford truck it is all redone and weighs about 2200 lbs. so power to weight ratio will make it very quick. I am really ejoying this site and thanks again for all the infh the engine is right under 400hp.

 

[joelster]

I run 11.75-1 compression, and pump 93. It will run on 91 but I've never beat on it with 91 in it. 38 degrees of timing all in by 3000rpm. Aluminum heads and the motor is reverse cooled. No knock sensors, and a relatively hot plug, Autolite 3923. The tune is pretty good. If you find your car slightly detonating, try a colder plug and see what happens.

Aluminum heads make a huge difference in helping to curb detonation. Every LS engine made has them.

I would cure the problem before I pay $15 a gallon for race gas. Colder plugs, less total timing, richer air/fuel mixture can all but eliminate detonation.

 

[cool rockin daddy]

I would re-think the entire combo. You're at 400 HP now but 420 HP is easy to do now with 9.5 compression, a relatively mild cam, and a good set of modern heads. Why run on the ragged edge of destructive detonation or seriously castrate the engine by de-tuning it?

 

[timothale]

double hump cracks ?

I have seen a few double hump heads with cracks between the center two exhaust valves. be sure to have them checked for cracks. with the 2 exhaust valves that close together , the heat is concentrated there.

 

[67Mustang Al.]

We ran a stroked out BMW in a 5 day race event here and made the finish line. We used E85 blended ethanol to give us a respectable amount of power at 7000rpm+ .You need 30% more ethanol than gas to cover the same distance. We spent $2000 on drums of fuel and had about 60 litres left.
More BHP, more fuel, more money.
Whoever has the deepest pockets can afford the most power. Our pockets are running low now. Pump gas for me, unless of course racing beckons.
Al.

 

[Thumpin455]

I switched to E85 and started making fuel at home from cattails and grocery waste. Its as simple as a carb swap, or just pull it apart and modify it with numbered drill bits. I modify Qjets to run ethanol, they work quite well for it. It doesnt usually cost 30% drop in mileage, even though you have to increase the fuel flow about that much. Up here E85 is $3.08 as of two days ago, and we are almost always higher than most of the country. Compare $3 to race gas prices and even if it did take a 30% hit in mileage its cheaper by far.

You can run over 13:1 with E85 pretty easy. The 455 in my 70 GTO has right at 13:1 and a 700R4/3.42 12 bolt behind it. It doesnt get hot, makes a ton of power, and at oil change time the oil looks just like it did when I put it in.

Octane boosters dont work, retarding the timing and running it as cold as possible on gasoline hurts power and mileage. If you have EFI its simple, just put half a tank of E85 in it, if its carbed its easier to switch to E85 than to figure out how much ethanol is in each tank.

Go here http://e85prices.com/e85map.php and enter your town in the search bar. It will show you the stations carrying ethanol near you.

 

[Mojo56]

I switched to E85 and started making fuel at home from cattails and grocery waste. Its as simple as a carb swap, or just pull it apart and modify it with numbered drill bits. I modify Qjets to run ethanol, they work quite well for it. It doesnt usually cost 30% drop in mileage, even though you have to increase the fuel flow about that much. Up here E85 is $3.08 as of two days ago, and we are almost always higher than most of the country. Compare $3 to race gas prices and even if it did take a 30% hit in mileage its cheaper by far.

You can run over 13:1 with E85 pretty easy. The 455 in my 70 GTO has right at 13:1 and a 700R4/3.42 12 bolt behind it. It doesnt get hot, makes a ton of power, and at oil change time the oil looks just like it did when I put it in.

Octane boosters dont work, retarding the timing and running it as cold as possible on gasoline hurts power and mileage. If you have EFI its simple, just put half a tank of E85 in it, if its carbed its easier to switch to E85 than to figure out how much ethanol is in each tank.

Go here http://e85prices.com/e85map.php and enter your town in the search bar. It will show you the stations carrying ethanol near you.

You are one brave man here... taking a stand in favor of the boogie man...E85.

I remember when we first started using unleaded gas back in the 70's... no engine would last more than 20,000 miles it was said. The heads would glow cherry red we were told...

Be ready for the naysayers...

 

[LATECH]

I would be open to running E 85 and a blower. That would be Kool.
I dont have the funds for it, at least not now.....but.
Alcohol only scares me when people drink it.

 

[1971BB427]

I have seen a few double hump heads with cracks between the center two exhaust valves. be sure to have them checked for cracks. with the 2 exhaust valves that close together , the heat is concentrated there.

Curious what kind of SBC heads have two exhaust valves together close enough to crack? There's one exhaust and one intake per cylinder/chamber, and quite a spacing between even the 3/5 or 2/4 chambers.
I've seen cracked seats between intake and exhaust on old heads, but never between exhaust and exhaust.

 

[Thumpin455]

You are one brave man here... taking a stand in favor of the boogie man...E85.

Be ready for the naysayers...

Have already had plenty of run ins with the naysayers, thing is most of them have no first hand experience with ethanol. I have first hand experience and have been running it for years, building carbs, engines, and not using anything exotic, just slightly modified stock stuff. Usually modified with a drill bit.

You hear or read stuff about how horrible it is, but really that is all just BS. The stuff flat works.

What octane an engine needs depends on a bunch of things. Chamber shape, bore size, material the head is made of, quench, piston design, cam specs, altitude, ambient temperature, any oil in the chamber and ignition timing all play a big part.

All aluminum modern engines like the LSx engines can utilize more compression on pump gas, older engines with iron heads need more octane for the same compression. Premium 93 wont work at 10.5:1 with most older engines that are all iron, even when you retard the timing to the point where it has no power anymore. It needs more octane than that, and there isnt any getting around it.

 

[my87Z]

my engine is 11.2:1 and I mix 5 gallons of 110 octane with 10 gallons of 93 octane to keep it happy. I got smart and bought a 55 gallon drum with an electric pump, this is where I keep my 110 octane fuel. I go straight up to our local dragstrip and fill it up, because i'm buying 55 gallons at a time, I end up getting it for about .40 less per gallon.

 

[ericnova72]

Cans of octane booster are a waste of time. If it advertises a 3 point gain when used in recommended amount per gallon - that is really only a 0.3 gain :nono: ., ....but they don't want you to know that. Your 91 octane would only become 91.3 .

Another vote here for E85 if you can get it in your area or are willing to blend your own using a barrel of E98. I know several racers in my town using it in street or street/strip cars with no problems and noticable benefits in power and easier engine cooling. Getting ready to go E85 myself on a 13.5-1 comp 406 SBC, my chosen carb is at QuickFuel Carberaton right now getting the correct boosters installed to properly match up to E85 (950 Holley).

If you don't want to go E85, the race gas/pump gas blending is an easy alternative as mentioned. 11-1 with old Fuelie heads will be fine on the 20-40% blend as by F-Bird. I'd expect with ignition and carb properly tuned the 20% figure will be fine.

A note on blending--- a 50-50 mix of 87 pump and 110 race actually comes out higher than the math would suggest. Math says 98.5 octane for this mix, but because race gas has so much lead in it, the real mix is actually closer to 100 octane---a little real tetraethyl lead goes a long way, you get "octane creep" in the mix.