What kind of fuel do you run?

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ajarofclay

ajarofclay

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Hey all, I was just curious what you are running now in these days of NoLead. I put my car away for the most part when the GOV had just started the ban. I used an additive for the most part or would get some racing fuel from Gas City back in the day. I had some fuel left in the tank that probably sat for 30 years and drained it recently so I need some advice on what to put in when I kick it over, hopefully soon. Thanks in advance...
 
I use alcohol free from Maverick gas stations.

The engine was rebuilt in the 80s and may or may not have replacement valve seats.

I'm not too worried about the lack of lead in the fuel.
 
In my truck, 87. In Vixen my Valiant, 92 or 93. I always get it from the same place and try to use the same pump facing the same direction.
 
I suppose you might have some options in Illinois. Here in California it's 87, 89 or 91 unleaded, all with ethanol.

If you have hardened valve seats installed, lead is not needed. Lead additives are questionable, anyway, because they tend to just sink to the bottom of the tank. I use 91 because the high compression 273 Commando insists on it. Some people make a big fuss over ethanol but I have never found it to be a problem.
 
100LLtank 025.jpg
beeswingercruisemay162021 045.JPG
 
Non-Ethanol at $4.99 a gal. for this Carbureted Converted '89 318 here in Florida.

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20240514_161956.jpg


Fortunately it is only 5 minutes to everything in down town Palm Bay.

Can run a lot of errands for minimal gas when things are close by.


☆☆☆☆☆
 
Is this a race car? Then I cannot say.

If a street car,
you can pretty much correlate the gas required to the Cranking cylinder pressure, and to the head material/chamber shape/with a minor adjustment for Quench.

For Iron open-chamber heads, the rule of thumb is
160 psi max on 91
155 max on 89
150 on 87.
Add 5psi for a tight Quench

For closed-chamber alloy heads the rule of thumb is;
200 max on 91
195 max on 89
190 max on 87.
add 5psi for a Tight-Quench.

These numbers assume at WOT, with a max sized carb, and full-timing.
On the primaries only, you can likely run any fresh gas, unless you happen to have a destructive Quench in the redzone of 050 to 080..

Personally, I have been running 187psi or better, even 195 briefly, on 87E10 since 1999; with OOTB Edelbrock alloy closed-chamber heads and a Quench between 028 and 032; with a 750DP, and 34* Power-timing, which is all she needs..
Your results may vary.

if you do a compression test, on a long-time sitting engine;
you gotta do all eight, and when yur done, you gotta do it again but this time with a couple of oil-can squirts, distributed around the rings, left to soak, then pump the excess out with the starter, before you put the gauge back on. Unfortunately, this will make a mess. After the oiling, the numbers should all even up. unless some excess oil stayed in the chamber. The numbers will be always be artificially raised just a bit, due to some oil being stuck on various surfaces. When it fires up, the running engine will burn up the oil. Now she's ready for a true Compression test.
If the engine has recently run, oiling is not necessary, unless it was gas-flooded.

Some engine designs will be able to run a wee bit more pressure than I listed. But my numbers should be safe. Most of us cannot hear detonation with our loud exhausts, and even fewer of us run knock sensors. And detonation, even in it's least destructive form, must be avoided, cuz it breaks parts; if not the first time then soon.
Your job is to avoid detonation at all cost.
 
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AJ/FormS said:
Is this a race car? Then I cannot say.

If a street car,
you can pretty much correlate the gas required to the Cranking cylinder pressure, and to the head material/chamber shape/with a minor adjustment for Quench.

For Iron open-chamber heads, the rule of thumb is
160 psi max on 91
155 max on 89
150 on 87.
Add 5psi for a tight Quench

For closed-chamber alloy heads the rule of thumb is;
200 max on 91
195 max on 89
190 max on 87.
add 5psi for a Tight-Quench.

These numbers assume at WOT, with a max sized carb, and full-timing.
On the primaries only, you can likely run any fresh gas, unless you happen to have a destructive Quench in the redzone of 050 to 080..

Personally, I have been running 187psi or better, even 195 briefly, on 87E10 since 1999; with OOTB Edelbrock alloy closed-chamber heads and a Quench between 028 and 032; with a 750DP, and 34* Power-timing, which is all she needs..
Your results may vary.

if you do a compression test, on a long-time sitting engine;
you gotta do all eight, and when yur done, you gotta do it again but this time with a couple of oil-can squirts, distributed around the rings, left to soak, then pump the excess out with the starter, before you put the gauge back on. Unfortunately, this will make a mess. After the oiling, the numbers should all even up. unless some excess oil stayed in the chamber. The numbers will be always be artificially raised just a bit, due to some oil being stuck on various surfaces. When it fires up, the running engine will burn up the oil. Now she's ready for a true Compression test.
If the engine has recently run, oiling is not necessary, unless it was gas-flooded.

Some engine designs will be able to run a wee bit more pressure than I listed. But my numbers should be safe. Most of us cannot hear detonation with our loud exhausts, and even fewer of us run knock sensors. And detonation, even in it's least destructive form, must be avoided, cuz it breaks parts; if not the first time then soon.
Your job is to avoid detonation at all cost.
Click to expand...
My mild build 340 turned out to have 175 psi cranking pressure. That's with reducing the compression height of the pistons, and a .050 head gasket. Does that mean I'm S.O.L? Pistons are .018 out of the hole and the heads cc out at around 70.
 
Pump diesel for the diesels.
California 91 10%alky cat piss for the late model pony car (best available out of the pump, short of $12 100 unleaded race gas.)
Pump 91, plus a few gallons of 100LL avgas, (cause I have access now) in my iron head 10.5 to one 440. The 100 avgas in Arizona is cheaper than pump premium at a name brand station in california.
 
AJ/FormS said:
Is this a race car? Then I cannot say.

If a street car,
you can pretty much correlate the gas required to the Cranking cylinder pressure, and to the head material/chamber shape/with a minor adjustment for Quench.

For Iron open-chamber heads, the rule of thumb is
160 psi max on 91
155 max on 89
150 on 87.
Add 5psi for a tight Quench

For closed-chamber alloy heads the rule of thumb is;
200 max on 91
195 max on 89
190 max on 87.
add 5psi for a Tight-Quench.

These numbers assume at WOT, with a max sized carb, and full-timing.
On the primaries only, you can likely run any fresh gas, unless you happen to have a destructive Quench in the redzone of 050 to 080..

Personally, I have been running 187psi or better, even 195 briefly, on 87E10 since 1999; with OOTB Edelbrock alloy closed-chamber heads and a Quench between 028 and 032; with a 750DP, and 34* Power-timing, which is all she needs..
Your results may vary.

if you do a compression test, on a long-time sitting engine;
you gotta do all eight, and when yur done, you gotta do it again but this time with a couple of oil-can squirts, distributed around the rings, left to soak, then pump the excess out with the starter, before you put the gauge back on. Unfortunately, this will make a mess. After the oiling, the numbers should all even up. unless some excess oil stayed in the chamber. The numbers will be always be artificially raised just a bit, due to some oil being stuck on various surfaces. When it fires up, the running engine will burn up the oil. Now she's ready for a true Compression test.
If the engine has recently run, oiling is not necessary, unless it was gas-flooded.

Some engine designs will be able to run a wee bit more pressure than I listed. But my numbers should be safe. Most of us cannot hear detonation with our loud exhausts, and even fewer of us run knock sensors. And detonation, even in it's least destructive form, must be avoided, cuz it breaks parts; if not the first time then soon.
Your job is to avoid detonation at all cost.
Click to expand...
Great info, AJ. Thanks. Does sound a little scary though. The car is a '72 but the motor is a '70 340 with some very mild work done to it. I should have mentioned all that initially. I guess I'll have to do a compression test. Probably should do that anyway since it probably has about an hour running time on it in the last 30 years. ALSO, over the last almost twenty years since I last ran it, I've probably sprayed some WD into the cylinders about a half dozen times and free cranked it to try and keep the cylinders somewhat clean. I'm sure what didn't dry seeped through the down so I just did a fresh oil change. Will do another after it runs for a while. My biggest worry was the lead free gas but it sounds like that's not that big o' deal?
 
ajarofclay said:
Great info, AJ. Thanks. Does sound a little scary though. The car is a '72 but the motor is a '70 340 with some very mild work done to it. I should have mentioned all that initially. I guess I'll have to do a compression test. Probably should do that anyway since it probably has about an hour running time on it in the last 30 years. ALSO, over the last almost twenty years since I last ran it, I've probably sprayed some WD into the cylinders about a half dozen times and free cranked it to try and keep the cylinders somewhat clean. I'm sure what didn't dry seeped through the down so I just did a fresh oil change. Will do another after it runs for a while. My biggest worry was the lead free gas but it sounds like that's not that big o' deal?
Click to expand...
Unless you plan to run that car 10k/yr for about a decade, I don't think a lack of lead should be a concern.
I'd be more worried about the alcohol content wrecking the rubber in the fuel system.
 
Yeah, about the alcohol attacking the rubber, that is a known thing.

However, the EFI jumpers on my car made it to 23 years. That is to say, the one at the back from tank-sender to the main line, rotted out and the pump started sucking air. On principle, I swapped the front one out, from main-line to the pump, and the one at the back to my EFI-canister filter. The line from pump to carb is one-piece steel, so that was that.
The Holley DP doesn't seem to care about the modest 10% alcohol.
 
CFD244 said:
My mild build 340 turned out to have 175 psi cranking pressure. That's with reducing the compression height of the pistons, and a .050 head gasket. Does that mean I'm S.O.L? Pistons are .018 out of the hole and the heads cc out at around 70.
Click to expand...
No,
my numbers are only a guide. And the numbers are not actually mine. I just compiled them together from various sources, including right here from FABO.
There are other variables to consider such as the load/stall, time spent in the troublesome area(gears), inlet air temp, chamber shape and finish, cooling system temp, header efficiency,
You can alter the pressure with; retarded cam-timing, or a later closing intake event, or a cam with a different LSA.
And if worse comes to worst, you still have at least two options
1) alloy heads, and
2) an anti-detonant injection, such as water/methanol.

Just for an example, Currently, the pistons in my 367, are up out of the hole at ~007; and with an 039 gasket for a Q of .032, using closed chamber alloy heads. The Ica is somewhere in the window of 61>64 *, I'm having a brain-stall, giving me pressure of about 180>185psi. and she is quite happy with 87E10.
A big part of the open-chamber issue is lack of a tight-Quench to impart a super-sonic transfer of what is usually dead air on the far side of the piston away from the plug. That blast really mixes up the air and fuel molecules, and helps prevent pre-ignition, which is what usually leads to detonation.
If I had your engine, I would be very tempted to swap to alloy heads, and get the pressure up, together with a tight Quench.
But I get it, you might have a ton of money in the current heads, so sometimes you just do what yagotta do.

My combo has actually pumped a tic over 200psi, still on 87E10, which is the only gas that has ever been in the tank, besides the one time it went to the track for exactly four runs.
 
CFD244 said:
My mild build 340 turned out to have 175 psi cranking pressure. That's with reducing the compression height of the pistons, and a .050 head gasket. Does that mean I'm S.O.L? Pistons are .018 out of the hole and the heads cc out at around 70.
Click to expand...

No, you’re fine. Cranking compression has little bearing on detonation resistance. Thinking there are rules of thumb and **** like that is old wives tales and secret squirrel ****.

I don’t think people have a grasp of what octane is , what it does and doesn’t do, how octane rating is tested.

IMHO, most guys run way more octane than they need to. I think many guys would be surprised at how much power they may be giving up by doing so.

Neither the engine or the fuel have no clue or does it even care what the heads are made of. It has zero affect on octane requirements.

Get your fuel and timing curves in shape, control engine coolant temperature and don’t purposely drive the engine into detonation by lugging it to death and you can run pump gas to 12:1 and maybe a bit more.

You can’t just Willy nilly slap an engine together and run compression as high as 12:1 and think it will work. It requires a thought out plan.

The end result is higher than orthodox compression ratios can be run on pump gas and not lose any power. You might make more power than on race gas.

I’ve seen 100LL Avgas make 26 more horsepower over 110 race gas at 12.8:1 and I know a guy that 14.8:1 in a Nationally competitive desert truck on straight Avgas with a skosh of MMT in it.
 
I run all my cars on 87 octane gas with upto 10% ethanol. It never hurt anything, but my cars don't have high compression ratios. Also, years ago I did an experiment with E85 and ran a 50/50 mix in my obd1 92 Ferd bronco. Ran it like that for a good time, it ran great and the computer was able to cope with no issue. As for the hoses and other seals in the system... they held up just fine.
 
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