How do I know what racing fuel to buy?

[NiceGuyEddie]

https://vpracingfuels.com/product-category/racing/

There used to be a place near California Speedway in Fontana that sold VP Racing fuel by the gallon. I added ONE gallon the day before an autocross and the engine seemed to run cooler, and it smelled not nearly as bad. Smelled pretty good, actually.

Anyway, I was surprised yesterday to pass by a VP Racing gas station in San Pedro. I stopped in and it turns out they sell the racing fuel in 5 gallon cans only, starting at $60. I don't recall any choices last time - it came from a pump. The place yesterday they had all sorts of fuel on the shelf.

They said there was no one on staff that day to help me select the right racing fuel (Sunday late afternoon - repair shop closed, etc.)

I'm sure you'll blow all sorts of things running straight race fuel but again, I'm just looking to add a gallon to a full tank.

I have a 347 with a 570cfm Holley Street Avenger (yes, small for a 347), Edelbrock aluminum heads, fuel pressure regulator, and an electric in-tank fuel pump if that matters.

If anybody thinks this is a bad idea, please tell me.

EDIT: When I tried the gallon of race fuel, I had a mild, 300hp 306.

[Railroad]

This chart puts it all in front you.
https://vpracingfuels.com/master-fuel-tables/#fuel-tables

[NiceGuyEddie]

Now I'm MORE confused :confused:

[frankeeski]

What ever fuel your carb or fuel delivery system is set up for is what you should run ALL the time. Unless you have a different tune for your setup to run the higher octane, you're just wasting your money.

[NiceGuyEddie]

Hi Frank:

How are you, old friend? (OB1-Kanobi voice)

Well, to your point, my carb was tuned for my old 306. I was just hoping to get the smell down and don't want to blow anything up.

I don't mine one (1) $14 gallon of race fuel per tank if it will do so. I'm only at 4-5 tanks of fuel per year.

I tried that "cherry bomb" fuel additive one time. I thought it was snake oil, but someone told me it really works and it really did. Of course, I wouldn't sniff it purposely or use it as an air freshener for my garage.

[Jeff Kleiner]

What ever fuel your carb or fuel delivery system is set up for is what you should run ALL the time. Unless you have a different tune for your setup to run the higher octane, you're just wasting your money.

Frank,
I think Eddie just wants it as cologne, not actual need ;)

Jeff

[sread]

If you are only going to add a gallon, it probably won't make much difference which one you choose. If you want to gain any real performance benefit, you probably would need to up the percentage to 50 % or more and would need to tune for it, i.e. add timing and or more fuel. Your main choice is whether to use leaded or not and whether to use oxygenated. You are running a carb so it won't hurt to use the leaded fuel but I think those are typically for higher compression builds, boosted, spraying nitrous , etc. Your best bet assuming you are running a moderate compression ratio is probably to use one of the oxygenated fuels with the lower octane rating. The r +m/2 number is what you see on pump gas so you can compare apples to apples. I think MR 12 used to be popular with the stock compression street car crowd and also u4.4. Both of those are probably going to cost more than the $12/ gal though.
Realistically, they will probably only have 4 or 5 to pick from, not everything you see on the list. You can also look at the vapor pressure numbers (less is better) if you are have any vapor lock issues.
If you are just running it to get the great smell, just stick with the most economical.

I just remembered something - you should probably stay away from the MR 12 - I believe they recommend draining the tank daily as it is very hard on any rubber./plastic components - some of the others also...be sure to check

[NiceGuyEddie]

Thanks for the lesson above. The prices at the store were between $60 and $200 (verbal, I didn't look specifically.)

I'll go back when someone is there, my guess is if I have a street motor with carb they'll know what to give me. I don't mind a $65 experiment.

In any case, I was very surprised to see the full-blown VP racing fuel station. Never heard of it.

EDIT: I just looked, and apparently, there are over a dozen VP Racing Fuels gas stations all over SoCal. One of them is near my workplace, one is near my "country home" and the other near my apartment downtown. They seem to have taken over a chain called "American Gasoline" and renovated every store. Gas prices are the same as 76 or Shell. If fuel for the daily driver is a quality fuel, I may have a new go-to gas station. But I guess that's another conversation.

I've opened my own can of worms!

https://scontent-lax3-1.xx.fbcdn.net/v/t1.0-9/68248115_10219990686421098_4670876002115649536_n.j pg?_nc_cat=103&_nc_ohc=gCg8sN2KpO8AX8mB3ZF&_nc_ht=scontent-lax3-1.xx&oh=517075bd9e631dbc232ad52b10f46d7d&oe=5EF85401

[Railroad]

I ran C10 like you did in my push rod, non O2 sensor engine. It does help. It cranked, idled and ran better than pump gas. I would add about 1 gallon every fill up somewhere around 1/2 a tank. It had a cumulative increase and insured I was at 93 or better. Pump gas is junk and any help is good.
I would recommend more research before doing this on fuel injected, computer controlled engines.

[NAZ]

Best case, you're just wasting your time & money. Your engine will not run cooler and there will be no performance advantage.

I run VP C12 because I have to but if the engine would run on pump gas that's what I would use. It costs me $171 for 15-gal and that lasts four to five passes depending on how full the staging lanes are.

[NC Cobra]

I’ll throw one additional consideration into the mix. If you can find a fuel source with no ethanol your carb will be MUCH happier. Pricing here in NC is about the same as premium.

[mike223]

You can also look at the vapor pressure numbers (less is better) if you are have any vapor lock issues.

If you are just running it to get the great smell, just stick with the most economical.



+ (mostly).

He can't possibly have vapor lock with an in tank pump.

As for the most economical (with the same great smell), that would be 100LL avgas - if you have any general aviation pilot friends.

[GoDadGo]

+ (mostly).

As for the most economical (with the same great smell), that would be 100LL avgas - if you have any general aviation pilot friends.

I used 100-LL for years in my old 1980 Z/28 at a 25/75 mix so that I could push my initial timing up a couple of degrees.
My goal was to just avoid detonation and it seemed to work well; however, I had no scientific proof to say that it improved the car's performance.
100-LL does have different burn rate than your typical automotive grade fuels, but I was only adding 5 gallons and topping off my 20 gallon with 93 premium.
The only takeaway for me was the car would rattle the pistons if I got a bad load of gas, but wouldn't if I threw 5 gallons of 100-LL Avgas in the sucker.

Old Z/28 Engine Specs:
10/1 Compression 350 SBC
Comp Cam 280 Magnum Cam
Edelbrock Performer RPM #7104
Quadrajet (Yes I Still Love Those Big Rear Flapper Carbs) built by Jet Performance
1 5/8" Header 3" Collector
2 1/2" Exhaust Dumped @ Rear Axle

Though Only A Peppy Car I Still Miss That Sucker!

[frankeeski]

Hi Frank:

Well, to your point, my carb was tuned for my old 306..............................and don't want to blow anything up.


And there, in lies, the issue. 570 CFM may or may not be enough for your 347, I know it wouldn't be for my 347 setup. How much fuel/air is used has more to do with than the limited specs you've given. Cam lift, chamber size and compression ratio matter. Second, a lean running engine "stinks" way more than a rich running engine. My suggestion would be to get together with your engine builder and find out EXACTLY what size carb you need and then have the engine tuned to 91 octane with that setup. I'd be willing to bet your smell issue subsides.

[TrevorP]

You motor should run fine on 91-93 octane. The smell is the carb. You're probably running rich and a rich fuel mixture is smelly. The race fuel has a sweet smell, so it is less of a nasty smell when burning.
My cobra runs on 110 octane. Even though the exhaust smell is very toxic, it has a good sweet smell. The Radical runs on 100 octane/sunoco 260. These fuels are required because of the very high compression and ignition timing to make more power.
You could try running your carb leaner, but at a risk of detonation if it becomes too lean. The best solution is to switch the carb out with a sniper fuel injection system. That way you can tune it to a much more accurate a/f ratio.

[Jeff Kleiner]

....Second, a lean running engine "stinks" way more than a rich running engine....

THANK YOU! THANK YOU! THANK YOU! Finally someone who gets it! I'd kiss ya' if you weren't so damn ugly so instead I'll just buy you a beer :)

Jeff

[GoDadGo]

And there, in lies, the issue. 570 CFM may or may not be enough for your 347, I know it wouldn't be for my 347 setup. How much fuel/air is used has more to do with than the limited specs you've given.

Excellent Point About Needing Complete Engine Specs!

347 @ 6,000 RPM

CFM @ 100% VE
602

CFM @ 90% VE
542

CFM @ 80% VE
434

The Carb May Or May Not Be Maxed Depending On The Engine Specs!

[NAZ]

I suggest before you do anything else, find a reputable shop that has a tuner experienced with carbs and have him tune your engine. A sharp tuner can advise you on the correct ignition system and carb for your application and can make it run correctly. There's no shame in getting expert help when you need it. If you don't have the knowledge to properly size a carb to your engine you likely don't have the skill to tune a carb. And this is a skill that is quickly vanishing as carbs are now typically limited to race engines.

I've been tuning street and race cars / motorcycles for more than 50-years and I know it's getting harder to find guys with carb experience but they are out there. You want a guy with carb experience, not some youngster that stares at a laptop tweaking fuel tables -- it's not the same. Find a shop that works on drag cars and you will likely find a good tuner with carb experience.

But don't think you're going to fix a tuning problem with race gas -- ain't gonna happen.

[GoDadGo]

But don't think you're going to fix a tuning problem with race gas -- ain't gonna happen.

NAZ,
If you are ever in or near New Orleans, drop buy and tune my car please!
Steve

[Jeff Kleiner]

...But don't think you're going to fix a tuning problem with race gas -- ain't gonna happen.

And you also ain't gonna' fix a tuning problem by working with the carb if the ignition curve isn't dialed in. It's a system and all of the elements play together.

Jeff

[Bob Cowan]

You can't tune a carb for a specific octane. It's job is to deliver a specific amount of liquid for a specific amount of air. You can only tune it to a specific air:fuel ratio. Various fuels and fuel mixes - e-10, e-85, methanol - will require more or less fuel. But gasoline is gasoline, as far as the carb goes. Octane doesn't matter.

Minimum octane required for a specific engine depends on a lot of factors, starting with dynamic compression ratio. If you run it too lean, it will detonate. People will think their octane is too low, but in reality their A:F is too high.

Also, the Octane of e-85 is about 110'ish. People look at that and think they can run 12:1 static compression. Unfortunately, that isn't true. That octane number is a bit misleading.

[NiceGuyEddie]

You guys are correct, and I'm aware that I'm far from an ideal setup. The engine was built for/with a Holley 850 double pumper. With that carb out of the box the car was stupid fast, but it bogged under heavy deceleration or even on a freeway cloverleaf at 30mph. At the time, I wasn't even close to being able to afford a full dyno tune of the engine: carb, weights in the distributor to change the curve, etc., so after I drove the new engine for about 250 miles I sold the 850 DP and put my 570 Street Avenger back on. The smell is not absolutely terrible, and it's only noticeable when at a stoplight. The car otherwise runs flawlessly - starts ice cold, idles ice cold, re-starts when hot, Etc.

Once again, I don't mind a $15 experiment. I'll eat a PB&J sandwich to make up for the cost. :) Sometime soon, I'll try a gallon of that 101 out of the pump and let you all know.

[NiceGuyEddie]

122754

I forgot to say that the engine builder is long gone so I'm on my own. I of course don't know as much as you guys but I do wonder why the carb was spec'd as an 850. I thought it's about double the CI so I'd use a 650 Double Pumper or 670 Street Avenger.

Cam above for any discussion.

[NAZ]

Good luck with that...

122755

[Avalanche325]

If you don't want to blow anything up, you had better tune that (preferably a larger) carb! If not, you could end up with blobs of alumium in your crankcase that you used to call pistons.

[OVCobra]

In gasoline, octane is not a thing or additive, it is a rating of the fuel's resistance to detonate. An engine's tendency to detonate is determined by the maximum cylinder pressure during the compression stroke (prior to ignition). The static compression ratio as affected by cam timing are the mechanical factors that greatly influence octane rating required. So the octane rating required for a given engine is determined by tuning for max. power (timing + A/F ratio). If the engine experiences detonation BEFORE achieving max power, a higher octane fuel is required. If max power is achieved without detonation, the fuel's octane rating is sufficient. Aluminum heads and 10:1 static compression ratio should be happy with 91 to 93 octane.
Running fuel with too high an octane rating can theoretically reduce power as higher octane fuels tend to burn "slower"; higher dynamic compression tends to increase burn rate so they work together.
As noted by Bob above, carb jetting will only affect the A/F ratio and is unaffected by octane rating.
Not sure the 570 cfm carb is too small but an 850 is definitely too big unless you are turning north of 8,000 or 9,000 rpm? You mention you are running aluminum heads but did not specify what make/model...depending on flow ratings of the heads, in combination with your cam timing and rpm, will largely dictate whether the carb is "right sized". If you are autocrossing, the smaller carb is probably a better choice with higher venturi velocity and faster transition response.
The smell that is generally associated with high octane fuels is the result of the presence of aromatic hydrocarbons, their molecular structure is interpreted by our olfactory system as sweet...it is not toxic!
Your desire to address a "stinky" exhaust can be caused by both too lean or too rich A/F mixture...have someone watch your exhaust to see if there is black smoke. In an autocross, the repeated on/off the gas will pour a lot of fuel into the engine by the accelerator pump.
The best advice is as noted above by NAZ, find a good tuning shop (carb & ignition) and get it tuned properly. Then worry about odours and race fuel if required.
Dave

[Avalanche325]

Even better on my opinion. Install and O2 sensor and do your own carb tuning. You can learn a lot and tune your carb. If that is not your thing, then get it to a tuner.

I agree with everyone that all of your specs are needed to get an estimate of the proper carb size. The carb size is more about how much HP your combination can make than the cid. The old charts of CI vs cfm were good when a "hot" engine made 1 hp / ci. They are no longer relevant. A stroker can suck in air / fuel well above its old school ci numbers. A reasonable 347 car easily use a 650. A strong one can take 750 to get the most out of it. It all depends on the combination.

Why not call some of the carb tech lines and give them your specs so that they can recommend a size? I did that with my engine builder, QF and Holley (back when they were separate). They all said 750 for my 347, which is 500+hp.

[mike223]

The engine was built for/with a Holley 850 double pumper.

The car otherwise runs flawlessly - starts ice cold, idles ice cold, re-starts when hot, Etc.

Sometime soon, I'll try a gallon of that 101 out of the pump and let you all know.


The 347 was sent out with an 850DP - this "disqualifies" the original builder from further consideration unless eddie specified a 10k redline nascar engine (I doubt it).

"The car runs flawlessly" with the 570 - means "it's not too far out", IMHO.

A gallon of race gas mixed in for sweet "cologne" isn't going to hurt anything (IMHO) - I've done the same thing (but I always pushed the limits of ignition timing, and compression, and all other limits too - and usually I was mixing premium unleaded + leaded race gas - 50/50).


The rest of the advice is "very credible" - but "a little carried away" considering the original question - but I know everyone is trying to help the best they know how ;).


And I do love the smell of race gas.

[sread]

The 347 was sent out with an 850DP - this "disqualifies" the original builder from further consideration unless eddie specified a 10k redline nascar engine (I doubt it).

"The car runs flawlessly" with the 570 - means "it's not too far out", IMHO.

A gallon of race gas mixed in for sweet "cologne" isn't going to hurt anything (IMHO) - I've done the same thing (but I always pushed the limits of ignition timing, and compression, and all other limits too - and usually I was mixing premium unleaded + leaded race gas - 50/50).


The rest of the advice is "very credible" - but "a little carried away" considering the original question - but I know everyone is trying to help the best they know how ;).


And I do love the smell of race gas.

I'm with you mike - I thought the original question was if it was OK to run a splash of race gas in the tank once a while just for fun and to get that nice smell....nothing said about the car not running right

[TrevorP]

I think a 650DP would be perfect size for your motor - it will be smelly though. The 570 street avenger may be fine. I'm not really sure what a lean running engine smells like, since more than likely it wouldn't last very long enough to smell. Lean is really bad, you can get away with a rich running engine. Stoichiometric for gasoline is 14:1 air/fuel ratio, but 12.5:1 will give you max brake hp. So, running rich makes more power anyway. Carbs are too hard to run a nice a/f ratio all the time. Atmospheric pressure changes the a/f ratio. The only way to not have a smelly engine is to run FI.

My 600hp race engine uses a 750DP. They engine builder dyno'ed with both a 750 and 850, the 750 made more power.

[AC Bill]

Now I'm MORE confused :confused:

That chart didn't help me one bit either..lol :(

[NiceGuyEddie]

A lot of good reading material as usual.

Turns out the VP Fuels by my workplace didn't sell 101 at the pump so the Google Review photo must have been from somewhere else. The place was MOBBED because their cash price is super low for fuel but that's another story. I was still able to talk to a guy that worked there. Pomoma dragway is just a few blocks away and he said they get in all sorts of stuff the week before sanctioned races. I wouldn't ask him for advice since the gas station was mostly a "vape shop."

I won't be trying this single-gallon 101 cologne anytime soon, but I'm still glad I asked about it. My thread subject title could have been better.

I'm only at a few hundred miles a year on the car (gotta fix that) but in the future if I have the time I'd love a new carb & tune.

[GoDadGo]

Eddie,

I'm the oddball and am running an 800 AVS Edelbrock.
I've been happy with the carb but would like to go to the AVS-2 which now has annular boosters on the primaries.
Most guys totally avoid this carburetor; however, I find it works well and is extremely easy to tune.
You may want to check out that series of carbs as a possible option.

Steve