What octane level should be enough to run my  350/350 11:1 compression engine. The engine is stock with the addition of a mild cam in it. I just bought the car and haven't checked the timing yet - but when I really step on it I get valve ping. I put 93 pump gas and added a bottle of octane booster so far. 

With that compression ratio you need at least 93 octane. If the additive helps use it. You can try backing off the timing some and see if that makes a difference, though you might lose a little performance, but that could be preferable to a burnt valve or worse.

I've always used 93 octane plus a bottle of 104 octane booster. I found out last week that I can buy aviation fuel (100 octane) for $2.80 per gallon. Since i'm paying $2.69 for 93 octane plus $7 for the octane booster, the avaition fuel will be cheaper.

Is it safe to run the avaition fuel?

try checking out dealers around you that sell racing fuel and purchase it buy the 55 gallon drum. Then use 5 gallons of it per tank. For long trips I use octane supreme 130 http://www.kemcooil.com/product_info.php?pId=61 

I checked on the racing fuel too. It was $352 for a 55 gallon drum. That calculates to $6.40 per gallon.

So let's figure this...5 gallons of racing fuel @ $6.40 per gal =$32.00. 13 gallons of 93 octane @ 2.69 = $34.97 for a total of $64.97 to fill the tank. That's too rich for my blood, especially since I only get a little over 9 miles per gallon.

As for Supreme 130, I have too much lead in my foot. I don't need any in my gas.

Jim,
If you can get avgas,100LL, for 2.80 a gallon, you better buy a tanker full. Here it is 4.29 at the pump and a tanker load,10,000 gallons, is going for 3.59 per gallon.
Also the 100LL isn't for everyone. It still contains lead, hence the LL, low lead.
Regards,
Scott

Scott,

I was telling a friend that owns our NAPA store about the $2.80 per gallon for the aviation fuel and he didn't believe it either. So I had him call and they gave him the same price. This price isn't at the local gas stations, it's from the distributor.

Just in case you want a couple of tanker loads, here's the company and phone number. Campbell Oil Co. 910-862-4107.

Jim

    100LL is good fuel -but. My experience with it was - it runs hotter and had a great tendency to cause my carb to ice up in cooler temp. After a couple of months , car started to run bad. Did some checking and found I was loosing comprossion in the cycs. Pulled the heads and found the valves were showing signs of burning. I know this was not a problem because I had to replace a left side blown head gasket a couple of months before I started using the Avgas. Just my experience. You may not have the same problems and probably withe the newer high strength valve material today, it may never be a problem.

Jim

 

anyone ever heard of adding 10% toluene ???( painters use it ) i have read it in a book and claimed to be as good as octane boosters but much cheaper . 


Norbert

Toluene is a cleaner, not a lube.  As a result it can be a problem for the fuel system components.  You could cause some damage. kstyer38801.6392013889

A friend is using 100LL aviation fuel mixed with unleaded premium and he is very happy with the results.  I'm not sure of the price in NJ but it is not terribly more than premium.

He brings a couple of 5 gallon cans to the local airport and adds it @ home before a trip to the local gas stations.

 

I pay $2.95 for 100LL Avgas for my 59 Mooney here in Austin Texas.  But I expect it's going up with the next resupply at my local field.  There is a web site which gives the local prices of Avgas.  Try http://airnav.com/fuel/  100LL has a lot more lead than 93octane auto fuel.  I would mix it with the auto fuel If I were you.  I am not sure what the mix rate would be needed for 11:1.  My Lycoming is only 9:1 but requires at least 93 octane according to my owners manual.

John

This thread makes me glad that I have a bone-stock 350/270 small block!  It runs just fine on unleaded premium.  proracr38814.8310416667

Even after my engine mods I'm still running on 87 octane.

Funny thing, I just bought back my 73.  It is stock L48 350 8.5:1 comp, and I bought a reprinted owners manual (some idiot PO lost or threw out my original one).  I read through it for the first time last night (never bothered to, back in 73 when I bought the car).  The owners manual recommends minimum 91 octane.  All the years (1973-1982) and 86,000 miles that I drove it I used regular unleaded 87octane (85 in the higher altitude states), and never had a problem.  I just drove it 2,400 miles back to Texas from Calif and put in reg unleaded all the way with no problem.  Why would GM recommend 91 octane for this engine????  I don't think I want to switch to premium at these pump prices, but I don't plan on driving it that much anyway.  I have my Valkrie for that!

John

Fuel quality was a bit different then.  And ratings varied.  There are three ratings,  Research method, Motor method, and research plus motor divided by 2, which is what is used now.

I honestly don't remember which rating GM used then, or if it's a different one then used today.    The VW Beetle at that time required 91, but it was the same as today's 87.  It was 91 RON   Research Octane Number.

Fuel was commonly rated as just regular or high test.

kstyer38819.4763541667

My Owners manual calls for 91 RON.  So 91 RON is the equalivant to 87 octane unleaded regular today?  In any case I have used regular ever since I owned the car with no ill effects.

John

Yes 91 RON is the same as today's 87 unleaded.   That's why you had no problems.  It was the right gas.