Technical Octane Boost - which kind?

Hello!

The car is an OT muscle car, but the subject should not be.

The engine in question is a '68 302 Chevy small block (that should give the car away) rebuilt to factory specs. I'm not certain of the exact compression ratio, but I'm pretty sure it's around 10:1.

I just got it on the road, and filled up with 93 octane fuel, but I'm still getting some pinging, so I need to boost the octane.

There are several kinds available on Ebay, but I'd like to know if anyone here can recommend one that "works", i.e. eliminates detonation. Royal Purple makes one, Torco is another, Octane Supreme, and Max Boost are others.

The engine rebuild is fairly recent, and it's a numbers matching motor, so I will not be changing anything.

Advice welcomed...

Thanks...

Chris

 

Probably going to get a bunch of opinions here. My experience has been that the "additives" you normally find don't do much. I have an OT Mustang that had pinging and I tried several brands and several amounts per tank. Finally just re-tuned.

 

Differing opinions on the HAMB??? NO!!!!

That's why I love this place...

 

Probably better off getting a can of race gas and blending that in, instead of little bottles of booster.

 

Buy some race fuel and mix it, try one gallon of race gas to 10 gallons of premium and see how it does.

Add more until it runs right if that doesn't do the job.

Most octane boosters aren't worth a damn.

Backing off the timing is a performance killer and will make it eat gas like crazy, not an option in my opinion.

 

302's were 11 to 1 originally. Could be a bit higher if the heads were surfaced during the rebuild. Hotrodmyk is right about most of the commonly available octane boosters being primarily snake oil.

Sunoco has a super premium unleaded that's 95 octane if it happens to be available in your area. Its usually about 20 cents more than their premium.

Someone will no doubt recommend avgas, but there's a federal law against pumping avgas into anything other than an airplane. And no, they can't pump it into your 5 gallon can without breaking that law either.

Sunoco makes about 15 different grades of racing gas. Some unleaded and some leaded. http://racegas.com Little bit of lead has a tremendous effect on the octane of pump unleaded gas. If you contact the distributor of Sunoco race fuel in your area, they should be able to tell you how much of their leaded stuff needs to be added to take care of the detonation on your engine. Wouldn't surprise me if a half gallon of their 110 leaded would raise the octane number on a tank of 93 pump gas to the 97-98 range.

 

Try a little NITRO, that'll help 4 sure

 

Closer to 11.1 . Most boosters will only raise your octane a few points, not from 93 to 98, more like 93 to 93.5. maybe would look into a Meth injection set up. look into the distributor timing curve too.

 

You may find that when the cylinder walls bed in and friction diminishes the pinging may lessen.

 

as others have said ... try.
http://www.vpracingfuels.com/racing-fuel
i run the 51 on C-16

or

real lead---> http://tetraboost.com/

and they had piston slap till warmed up ,... the orginal 302's

 

I've heard if you're building an experimental airplane in your ba*****t, you may have access to Avgas 100LL.
That's just what I heard. Don't know nothin' about mixin' 5gal or so to a tank of premium. That would probably be illegal if you got caught runnin' it on a public thoroughfare. You my face severe punishment. If you got caught. Maybe. Full strength, they might send you straight to the chair. I also heard those hyper little oh-two's absolutely love the taste of the stuff. Crazy ain't it?

 

try to use some non-alcohol gas...A station near me sells 90 octane "lawnmower" gas.

 

Aircraft piston engines are maxed out on rpm at about 2000-2200 rpm and the fuel burns too slow for an rpm happy engine like a 302 sbc. Try mixing leaded race gas with premium 93, or you can set up a water and alcohol (methanol)injection system. Years ago I used an Edelbrock vara-jection unit with a lot of success, but unfortunatel;y the unit is no longer available. In this case Google is your frien as I think other similar uniots are still available.

 

Holley made em too( watermeth) sprayers...
ave gas is ALSO dry...
now what was that 5 or 6 ingredients we used to MIX back in the DAY...?
Ave gas/meth/highest obtain pump gas we could find/ some upper cylinder lubricant / and
ya 5 and 6 escape me (no not mothballs) ... or was it ...lol

 

Ping all the time or only when you hard on the juice? What "dirty old man" said. Build your own water/alky injection system. Container + washer pump + hose with spray nozzle ( used windshield washer metal piece ). Drill hole in air cleaner top and ****on inside. Push gas and push ****on - worked great. Search internet - sure to find ton of info.

 

Many/most good turbo cars use water/alky injection - most have/build more pressure then turbo - NEVER p*** liquid thru turbo. You just need simply system - vacuum at carb will **** it down. Have used little water + rubbing alcohol. Was not clear on "****on" - electric turn on ****on like a line lock ****on.

 

We all ***ume your timing & advance is correct. I always check marks on timing damper to "top dead center" to be sure marks correct.

 

AmishMike, wouldn't there be pressure after the turbo rather than vacuum or am I missing something?

 

Believe "Barsteel" is just running carb - will **** it down with low pressure from windshield washer pump. If turbo or blower must have high pressure pump to overcome blower boost.

 

The legal aspect of using AV gas in a car is that there is no road tax placed on the fuel sales, but, if you purchase 5 gals from your local gr*** strip operator, he probably doesnt care that your airplane is under construction and you need a test run of the Continental 0-470 engine. FWIW, Dont tell him the max RPM is 2000 to 2200, thats cruise RPM, depending on aircraft and prop, around 2700 RPM is max, after that the prop tip speed is supersonic and becomes inefficient. If they ask for an N Number, one could say the aircraft is not registered yet. If its a drag car its not operating on public roads anyway. One must follow all laws : Federal, State, county, city, and yo wife.

 

OK, I thought we were talking turbos with methanol injection.

 

My 32 runs good in Lucas octain boost and premium. It is the only obtain boost that I have seen work in my car.

 

I've read that common paint thinner and charcoal starter is the same stuff that most octane boost is. Dump a pint of it in every tank of gas. All you want to do is slow the burn down a bit, paint thinner (not lacquer thinner) burns slower than gasoline.

 

Thanks for all the replies.
The pinging isn't horrible, but it's there when I get on it (which is hard not to do ).
The car is all number matching, so I'm hesitant to change anything, and I want to preserve it as best I can.
I'm going to try a few of the commercially available boosters and see what happens. Snake oil? Maybe, maybe not, I want to test it for myself.
I'll check out Sunoco for the 95 octane fuel, but I've never seen it around the state (CT).
If all else fails, I'll look into alcohol injection.

Chris

 

I use VP Vintage fuel in my high compression cars. It is available in leaded and unleaded. Have mixed VP and pump gas in the past with some success.

 

Worth a read, perhaps...

http://www.hotrod.com/how-to/engine/fuel-octane-rating-comparison/

A quick google search netted a few test articles, but as with any magazine coverage they should be taken in context (cough-cough, advertising income).

 

Bar steel-you're missing the right solution-RACE GAS !! It is traditional ...[emoji5]️[emoji6], many 302's ran on it , and is smells great ! I race vintage Vettes, with up to 14:1 compression, and regularly mix race gas into my high compression road cars. IT WORKS ! The other chemicals are iffy, and alcohol/water injection messes up your numbers matching car. Try the race gas before going further- nothing to loose....

 

Looks like there's a couple places within 10 miles of monroe CT that offer sunoco race fuel, you'd have to call, it's usually a seasonal thing.
http://www.racegas.com/fuelfinder

 

The LUCAS booster does work very well. Try some!

 

I went with the water/alcohol injection for 383 in early '70's when gas went bad. It let me dial in more advance as you could really tell it was down on power when retarded. It still beat itself to death eventually and was replaced with a 440.