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Old 06-19-2012, 08:16 PM
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what to do if you have a high compression engine with unleaded gas today

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

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Old 06-19-2012, 08:56 PM
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Move to Colorado.
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Old 06-19-2012, 09:06 PM
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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.
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Old 06-20-2012, 01:09 AM
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What is your compression ratio?
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Old 06-20-2012, 04:46 AM
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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.
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Old 06-20-2012, 07:06 AM
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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.
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Old 06-22-2012, 10:42 PM
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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 info.Oh the engine is right under 400hp.
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Old 06-23-2012, 05:32 AM
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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.
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Old 06-23-2012, 06:46 AM
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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?
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Old 06-23-2012, 07:21 AM
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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.
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Old 06-23-2012, 07:37 AM
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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.
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Old 06-23-2012, 10:14 PM
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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.
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Old 06-24-2012, 09:01 AM
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Quote:
Originally Posted by 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.
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...
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Old 06-24-2012, 09:10 AM
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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.
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Old 06-25-2012, 03:09 PM
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To allow your 11:1 compression ratio engine to be all it can be you can mix 110 octane unleaded race gas with the best premium pump gas in your local area to get the fuel octane required.

You will probably want a blend ratio of 20% to 40% of the 110 race gas to pump gas.

Most good modern unleaded race gas also contains a lead substitute that prevents-reduces exhaust valve seat recession.

Good premium pump gas can handle around 10:5:1 compression.
Beyond that its a real good idea to help it out with a addition of high octane race gas. The exact amount needed to spike the octane up enough depends on many factors. Including the quality of the pump gas.

If you do a lot of street driving and not much racing its probably more practical to just replace the pistons or heads to get a more pump gas friendly engine compression ratio.

Little cans of octane booster are pretty much a waste of time and money for anything bigger than a mini bike.

www.proracingfuels.com
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