Due to my large cam (Comp cams XE 284),I run lots of timing, soft springs on the mechanical advance, and no vacuum advance. I run lots of timing as it gives me a smoother idle. Last weekend my engine started to ping on my last 1/4 mile run. I don't want to turn down my timing as it does not ping during normal street use, even under load.
I was thinking of using aviation fuel on those weekends that I race in order to increase my octain level from 93 to 105. Is this fuel safe to use on my car and will it help to keep it from detonating? My compression ratio is about a 10 to 1. More info on my sig.
Daniel


------------------
1967 El Camino, 350/.40 over,ported & polished camel back heads,750 double pumper, Comp cams 284 with .507/.510 lift,
Edelbrock RPM Air Gap manifold,Hooker headers,posi w/ 3.73 gears,induction hood, TH400 tranny with Quick silver shift kit, and ET Drags for traction, (1/4 mile = 13.112 @ 103.612 mph)

# 1 Av fuel smells like hell
# 2 There are a lot of additives in av fuel, to keep it stable in different temperatures and altitudes

....its not exactly good for your motor, but it will run on it.

With 10:1 c/r, you shouldnt be having these kinds of problems with pinging, so I would look into a mechanical solution for the problem before switching fuels

Daniel, VP makes race fuel with numerous Octane levels. I used 102 and I bought it at the track.



------------------
Larry
TC # 1000
66 Malibu - under transformation
Off the Frame (http://www.chevelles.com/showroom/lmacdonald1.jpg)
Back on the Frame (http://www.chevelles.com/showroom/macdonald2.jpg)

Av gas is designed for engine running uinder 2800 rpm, at high altitude. It has additives to resist icing. It's not a good fuel for cars.

------------------
Pat Kelley
66 El Camino, daily driver
67 El Camino, STRIP/street
Pat's Page (CR Calculator, Utilites, car specs) (http://cochise.uia.net/pkelley/)

I had a similar problem when racing in warmer weather. Most of the day my car ran great, but the last one or two runs it started to ping. If it is a street/strip car, and usually runs great around town, just put in a can of octane boost when you go to the track.
Unless your tank is empty before adding the racing gas, you are diluting the mixture anyway. I found it was a lot cheaper and easier to just add some booster only at those times needed, rather than try to hunt down a station that sells racing gas, pay the price to put enough in the tank to be useful, etc.

Daniel- av gas has 4 x the lead that reguler gas had in it when it was 40 cents a galon, very bad for skin contact and can sit for ten+years and not go bad, and yes it runs quite well in cars apx. 1/3 to 1 ive ran it i owned a cessna 180 tail drager for 5 years on floats- nuthin like taking your plane to the beach http://www.chevelles.com/forum/biggrin.gif

Awhile ago they had some drags down at the local airport(small) and they were leting people buy aviation fuel mix to race with. Bad part is it was like $5 a gallon or something! http://www.chevelles.com/forum/eek.gif

------------------
Justin

69 Chevelle SS (http://albums.photopoint.com/j/View?u=1331110&a=9900736&p=33007599) 425+ HP

97 ZR2 S-10 4x4 (http://albums.photopoint.com/j/View?u=1331110&a=9900736&p=33006416) with many mods to come!

"If it doesn't go, force it. If it breaks, f**K it, it needed fixing anyway!"

I've run run AV fuel in my GN with no problems what so ever. And it's cheaper than the gas at the tracks. But only because it doesn't have the road taxes tacked on to it. Wouldn't be a bad idea to hook up a ex temp gauge to make sure your not leaning the motor out. Better to play safe.

Av fuel runs hotter than your run of the mill racing fuel in Arizona or southern Cali. I would not touch the stuff. There are some good racing fuels to use Sunoco, 76, Blue turbo, and my fav Trick. On the average they run $3.50 to $5.00 a gallon in Az.

Most of the above is good sound advice. However, Aviation fuel is designed with anti-icing agents and does not have the "add-pac" that's required for automotive useage. One thing I discovered was that my car was sluggish off the line but on the top end seemed to be OK. This was with a 25% av-gas to 93 oct pump gas ratio. Over time it can harm your engine. VP will work better.

Don't you also have to rejet your carb in order to run avgas?

------------------

Mark
1970 SS454 LS6 (nom)
-------------------------
"Those who would sacrifice their freedom to achieve a measure of 'safety' deserve neither freedom nor safety."

Thanks for the advice,
I may just play it safe and use an octain booster like NOS or 104; any suggestions on a good booster? Or, must I shell out $7 a gallon for the local race fuel.
Daniel

Well, I just picked up a gallon of Lead Supreme 130 but haven't tried it yet. It's got good ole TEL in it and it looks like 12oz will boost 10 gals. of 93 up to 95-95.5.
The point boosts you get from the 104+ stuff are very slight, i.e. when the bottle says it boosts 5-7 points the means .5-.7. I'll keep you guys posted once the weather around here starts to cooperate.

------------------

Mark
1970 SS454 LS6 (nom)
-------------------------
"Those who would sacrifice their freedom to achieve a measure of 'safety' deserve neither freedom nor safety."

You can also add race gas to the regular pump mix to raise the octane a few points. If you are running a 10:1 motor you really should not need more than 93 to 95 octane.

If performance is your goal at the track then forget about the Av gas and run the race mix that is optimized for automotive engines at the altitude, temperature and relative humidity that you run at.

For the reasons stated above Av gas will likely do nothing more than create new problems and who needs that...



------------------
My 70 Chevelle Race Page
hometown.aol.com/mkrauser/gmracing/gmracing.htm (http://hometown.aol.com/mkrauser/gmracing/gmracing.htm)


70 Chevelle Fathom Blue
70 Malibu Convertible Midnight Regatta Blue

My '83 Honda CB1100F just LOVES 100 octane "low lead" avgas. (still has plenty of lead!)

This is an air cooled bike, (runs hot and pings in traffic) around 10:1 compression. Spins happily to 10,000 RPM. More, when you find a false neutral in the gearbox...

I have no idea what there is in Avgas that "wouldn't be good for an automotive engine" other than the lead additive and it's pollution problems.

At least when you spill 100LL on the tank, it evaporates without a trace. Pump gas spilled on a bike tank leaves an oily residue. Even the exhaust smells different. Try it, you'll like it!

Octane ratings are different in aviation fuels. Altitude is a prime factor. I wouldn't touch the avgas, stick with a race fuel/premium mix.