I have run 11.5 on pump gas without problems. It is not so simple as compression ratio only. Air Temps, loads, ignition timing, CAM TIMING AND DURATION, spark plug heat ratings.... ect. The valve rattle on a hot day is a precursor to detonation. It is clear.
Otherwise, just read your plugs and compare to online plug reading charts. The plugs will tell all.

 

My 1970 LT-1 will "rattle" on our cra*py Calif 91 octane "premium". I use an additive for lead and a octane booster, and still have to retard the timing to 34 degrees total advance to get by. Aluminum heads will help along with free flowing exhaust system, good water pump and radiator.

 

It's not the correlation beetwin high octane and first quality in the race fuels that makes me state they're high quality, they're simply first quality because the quality of the product itself and i tell you by experience...i've been mixing race and pump gas fuels all my life (well, since i was 15... ), race fuels are cristal clear, no need to add all the BS is needed in the pump gas to increase its octane ratings (to avoid lead use), no foreign odours (actually the one i've always used smells like vodka )...refinaries, like any industrie, can process different quality products starting from the same base at different costs and for a different nitch of customers.

By the way, the race gas i use is french...like the Evian water ...

 

You may want to take a look at this:

http://www.empirenet.com/pkelley2/DynamicCR.html

DCR is far more important than the CR alone. I am running 12.3:1 in my LT1 (granted, aluminum heads and reverse cooling), on 93 octane with no issues.

 

Sorry, are you confusing gasoline and bottled water? Sounds like you use the same criteria for each.

This is hardly 'proof' that racing fuels are higher quality. Different yes, better-how?

 

Mike, i'm not confusing mineral water and fuels

Like every product you'll find on the market, included fuels, there is good quality, medium quality and of course bad quality...it all depends on the kind of process and procedures these products go through...

In the very case of race fuels compared with common pump gas, you're right to say that the process is the same but what's different (...and makes the market price different as well) are the tolerances in the quality and the quality control, you might notice that you could eventually incurr in bad quality pump gas, even of the same brand, if you might change pump distributor (this has happened to all of us)...well, this happens because the quality tolerances batch to batch are pretty 'open', a pump gas needs only to arrive to a certain level of refinement to be good enough to stay in a pump distributor, a race fuel is better checked and more accurately processed, and before beeing put on the market the checks on each batch are wider and more accurate.

This difference in the accurancy of the process and quality check makes me say that race fuels are of a superior quality and you should expect them to be of a more constant quality then a normal pump gas.

This is only my personal opinion of course and i could easily be 100% wrong and you might be 100% right...

 

Race fuel MUST be in a very close tolerance!
....due to the fact that any race engine is running allways on the edge!

One thing to remember is that (at least in Italy) race fuel is quite allways oxigenated..... and in some case you have to richen your carburation in order to avoid very hot combustion..... able to litterally melt down pistons and heads (not iron heads, of course).

Furthermore the combustion process of race fuels can be very faster, asking for less advance!

 

Aurora, Oregon

 

Again, you're going on a bunch of assumptions that can be applied to any goods that are being marketed as being 'better'. Like Evian.

You apparently have no quantitative or qualitative parameters to back up your claims.

Yes, the octane rating is higher in most racing gasoline, this can be 'measured' by the tendancy of an engine to knock when operated with lower octane gas. That's an easy one.

In what other ways is 'racing gas' better quality, and how does this affect engine operation, durability or reliability?

 

You could mix in an alcohol with your fuel. I would think it would be a cheap alternative. Make sure you have the pure product and readjust the jetting of the carb.

Furthermore I would check that you are drawing in cold enough air to avoid detonation or maybe reduce the timing somewhat if you want to run on the current gasolines.

 

Ok, I quit, you're right and my ''assumptions'' are totally wrong

 

The Octane Booster does something. I know of a time when 89 was tried on an engine and had all kinds of problems. The booster made the car very driveable. It was later determined that the car needed at least 91 octane to drive...

 

I used to drive to the local municipal airport and buy avgas by having them pump it in 5 gal. Jerry Cans. Eventually, the man I was buying the gas from got to know me well enough that he would pump it right into my car. I think it's somewhat unlawful to buy avgas for use in a car.

I would mix 5 gallons of avgas into my 20 gallon Corvette tank. The other 15 gallons was 91 (or 92) octane. My 11.5:1 piece part built L88 was happy with that mixture. (I had the original L88 piston heads milled down a little for the lower compression.)

 

I have about the same set up you do and I use octane booster without any trouble, but I have not driven it on a Missouri hot day in summer when I do I think 2 gal of race gas will work,you just have listen to the engine under load I have thought about setting it up for E-85 but I am not sure what that involves.

 

Timing is definitely something else that could effect it. I was running 89 and it seemed to knock a little in hard acceleration. I backed of the distributer a bit and it fixed the problem. Ran just as well if not better, and the knock wasn't noticed. I switch to 91/93 though just to make sure, don't want to ruin a perfectly good engine.

 

Here are two additional options:

http://kemcoindustries.com/product_info.php?pId=61

http://maxlead2000.com/

Both are TetraEthyl lead...the same stuff used to increase octane in leaded fuel for 50 years. Don't use it if you're running catalytic converters.

The product in the top link comes in easy to use quarts and is what I use. The bottom link I've never used. It's cheaper but looks to come in gallons and you'd have to deal with more handling. It is toxic so that is an issue and why I use quart bottles.

 

The Kemco instructions say to add 8 ounces of their product per gallon. ???? Is this a typo? For a 20 gallon fuel tank, I have to add 160 ounces? That about 2 1/2 gallons of additive I think. Maybe add 8 ounces of their product to a gallon of fuel and then pour that mixture into the gas tank?

Thanks

 

Depends on how much adder you want. 93 octane is usually close to enough so I mix mine to about a 96 (I'm running 12.5/1 static compression ratio but dynamic is much lower based on my cam specs.). Based on going from 93 to 96 and getting a bit of lead lube on my old valve seats, I add about 10 oz per 20 gallon fill up. I get no detonation at 96 octane with 36 degrees timing and iron heads. I could probably get by with less, but from the research I could find, about .25g/gal of TEL is the minimum you can run and get valve seat lubricant benefit. I've run straight 93 before when I got caught without a quart of TEL and didn't get any detonation on almost a whole tank of fuel....but I didn't try push things until I had a chance to add some lead and get it into the carb.

Only mix for what you need. Experiment with it a bit, but once you hit the octane sweet spot, higher numbers are just a waste of cash and effort. Here's the chart from the site.

0.6- Ounces OS-130 to 1 gallon/fuel……….2.0 point octane increase
1.2- Ounces OS-130 to 1 gallon/fuel……….3.5 point octane increase
1.8- Ounces OS-130 to 1 gallon/fuel……… 5.0 point octane increase
2.4- Ounces OS-130 to 1 gallon/fuel……….6.5 point octane increase
3.0- Ounces OS-130 to 1 gallon/fuel…….…8.0 point octane increase
6.0- Ounces OS-130 to 1 gallon/fuel……..11.0 point octane increase
18- Ounces OS-130 to 1 gallon/fuel……..16.0 point octane increase

 

I know the math on what I add didn't work...reality is I add 10 oz of TEL and then top off the tank. My normal top off is 10 to 12 gallons. Sorry if I confused things.

 

Isn't this all a moot issue unless you tune the eng to run with what is currently in the tank?