I tore apart a '66 327/300hp engine that had been run 100,000 miles on unleaded gas. The head shop said there was no damage because of it. Attached are some snippets from old VetteNet postings and private email relating to leaded gas and octane boosters. They are taken out of context and not arranged in any order. -- Greg ---------------------------------------------------------------------- Private Email from Jim Lockwood I've looked at this same problem for the last few years. My first choice is to find a source of leaded gas with at least 1 gm/gal of lead. For a while, this will continue to be an option, but the handwriting is on the wall....all lead usage will eventually cease. For now, though, my choice of lead sources would be racing gas. The formulation we run in the RPO '57 race car has 8 gm/gal of lead even today. So you could cut it approximately 8:1 with street gas and still end up with your 1 gm/gal minimum. The cost of racing gas, though is around $4.00/gal. So my second choice, and really I think the correct choice, is to rework the heads to tolerate unleaded gas. The best info I've found indicates that the head itself must be modified. Simply installing hardened valves isn't an answer because it is the soft iron head that deteriorates, not the valve. The rework involves milling a groove around the exhaust valve area such that a hardened ring can be pressed in as the new valve seat. The one down side to doing this that I know of is that some older heads do not have enough metal around the valve seat and the milling operation can penetrate the water jacket. Doing so, ruins the head. I've heard of this happening only on heads manufactured in the '50s (unfortunately, I have no fewer than three '50s era cars that need this work :-( ). I haven't heard of any problem with heads manufactured in the '60s. An alternative, if you don't mind the loss of originality, would be to find some '71 or later heads and use them. Starting in '71, all GM engine heads had hardened valve seats and coudl withstand unleaded gas. This is likely to be the simplest way to get a long term solution to the problem. If you elect to take this route, though, you should still retain the original heads. Someday you may want to use them or maybe sell the car to someone who is a bug on originality. ---------------------------------------------------------------------- Private Email from Jim Lockwood I realize I didn't answer one of your other questions: > When makng it high performance, i.e. higher compression pistons, > what are people doing ? Lead additives? Airplace fuel? Octane boosters? I'm not convinced that the Octane boosters do much. I ran 104 Octane Boost a few years ago when I drove my '63 to Bloomington. At every fillup, I added a can. The *only* effect was that the deposits on the plugs turned yellow. The engine still knocked and pinged just as badly as when I hadn't been using the Octane boost product. A fair strategy today might be to go with relatively lower compression pistons (like I did with my '60), and diddle around with the cam and heads to get a free breathing engine. The high compression definitely would be a Good Thing, but you can compensate for its loss in other areas and then you don't need hi Octane gas. For what it's worth, with 9.5:1 pistons, I can run 89 octane gas and the '60 doesn't knock at all. ---------------------------------------------------------------------- Roger A. Goff > (To the person saying he was looking for an older Vette.) > When dad restored our 1960, he had a local engine builder convert it for > unleaded gas. That might be the way for you to go. Hmmm. Let me expand on Joe's comment a little. You don't really convert and engine to burning unleaded gas. What you do is enable the burning of unleaded gas. This is accomplished by putting hardened valve seats and hardened valves into the heads. To really convert an engine to unleaded gas, to me, would mean doing the above plus adding a catalytic converter and other pollution control stuff. I agree that you should enable the use of unleaded gas because it's the only pumpable premium that I know of (other than those of us who've figured out where we can buy AV gas for competition, etc.). ---------------------------------------------------------------------- Jim Lockwood Starting in '71 Corvettes came with hardened valve seats and could run safely on unleaded gas. If you are looking for a driver and aren't inclined to do the surgery necessary on a pre-71 motor to make it run on unleaded safely, then a 71 or later would be a good choice. ---------------------------------------------------------------------- Geoff Swavley University of New South Wales We still have leaded petrol at every garage, therefore 60-70 model engines just love Australia. ---------------------------------------------------------------------- Jim Lockwood A compelling advantage to running r**ing fuel, especially in older cars (for purposes of discussion older == pre 71 GM) that need lead for valve seat protection. At least one formulation of r**ing gas I've seen locally has 8 gm/gal of lead. Contrast that to a generally accepted minimum needed value of 1gm/gal to prevent valve seat wear and it's clear that r**cing gas will get the job done. As to the viability of octane boosters.....my only data point is with the 104 brand of octane booster. When I drove my '63 roadster to Bloomington a few years ago, I packed a case of this stuff and dumped in a can each time I stopped to fill up. Although it turned the plugs yellow, I couldn't tell that it made any difference on the 10.5:1 327.....it still knocked miserably under load. If r**cing gas was convenient (note that I didn't say cheap....it isn't. Out here it's around $4.00/gal.) to buy, I'd mix it with pump gas in a ratio of 8:1 (to keep my 1gm/gal of lead) and run it in my old iron. ---------------------------------------------------------------------- Lloyd Johnson Someone asked about racing gas vs. octane booster so I thought I would give you my experiences with the subject. I drove a Corvette with 11.0:1 compression on the street and in SCCA autocrosses and hill climbs way back when 100+ octane gasoline was still available from the pump at your neighborhood filling station. Over the years the quality of the available pump gas degraded and I was forced to use octane booster. I would add 1 can of 104+ octane booster to a tank of unleaded premium (18 gal.). This worked pretty good for street driving but I could detect some audible detonation under heavy acceleration in competition. I decided it was worth the possible engine damage to continue to run the mixture since most of the miles I put on the car were driving to work and I only competed with it 2 or three times a month. Racing fuel was much more expensive and not redily available. This didn't cause any problem for about 3 years. Finally the inevitable happened and I burned a piston during an autocross due to excessive detonation. It was no big deal, the only work that was required was a new piston, a rebalance, and removal and installation of the unit from the car. There was absolutely no damage to the valves, valve seats, or valve guides. I did decided, however, that the time had come to start using higher octane fuel and to limit the miles I put on the car through street driving. I used 100 octane aviation gas for a while because it was available at the local airport at the time and was about 1/2 the price of racing gas. The av-gas worked satisfactorily and never gave me a problem. Eventually the law changed and I could no longer purchase av-gas from the airport and I was forced to further limit the street miles I put on the car and run racing gas. Some gas companies, Union 76 comes to mind, still sell 100 octane unleaded. I have used this when I could find it and it worked fine also. Most of the time I use a mixture of 3/4 unleaded 93 octane pump gas amd 1/4 114 octane racing gas. There are some advantages to running the lowest octane gas required to keep the engine from detonating. First is cost, racing gas costs $4-5 per gallon depending on the octane rating. Pump gas is only $1.25. Secondly, contrary to what most people believe, higher octane gas does not in itself give you more horsepower. It allows you to produce more power from an engine by increasing the compression ratio limit before you reach detonation. The higher octane fuel actually burns more slowly and produces less energy to be turned into power than the lower octane fuel. I'll probably hear a lot of static from people that don't belive this but that's O.K. Use what you think is best and I'll beat you to the finish line. ---------------------------------------------------------------------- John R. Lupien How much of which kind of lead additive did you add to what grade of gas? I have used some of the "RealLead" additive in my air-coled flat-four, with good results. I added it to 94 octane Sonoco, at about the recommended mix, and got a noticeable improvement in low-rev on-throttle performance. > Am I imaging things, or is this a benefit of the lead additives? If you have a high-compression (and maybe high-temperature) engine, this is precisely the kind of effect that the high-octane leaded gas was supposed to have. ---------------------------------------------------------------------- Jim Lockwood In '71 GM dropped the compression ratios of all their engines and made them compatible with unleaded fuel. Some power loss and performance loss resulted, as you'd imagine. ---------------------------------------------------------------------- Roger A. Goff I believe '75 is the first year for emissions controls, of any variety, on a 'vette. But the '74 certainly did not have a catalytic converter which was the big horsepower killing device. What you were seeing in the period from '72 through '75, was a decrease in the compression ratio of the engines to accomodate the lower octane fuels and attempt to improve fuel economy. ---------------------------------------------------------------------- Phil Gunsul 1969-71 had an Octane Adjustment Unit and staring in '70 there was a relay on the trans to control the spark. 1971 saw a drop in compression ratios from the '70 low of 10.25:1 to the to the '71 HIGHEST ratio of 9:1, with a drop of about 30 h.p. on comparable engines. ---------------------------------------------------------------------- Dave Bright > What advantage is there to using something like Sunoco r*cing fuel > versus using less expensive octane boosters to ordinary premium pump > gasoline ? > > Does the racing fuel have other components? Do the octane boosters > not work very well ?? I'm sure you'll get different answers here and it'll also depend on what year vette you are talking about. But on late model vettes I'll say this. Most of what I have read is that you don't need to put in any higher octane then what the manufacture recommends. That higher octane then what is recommended won't make any difference in performance. Well I for one believe in putting the highest octane I can get which is Sunoco 260. For the following reasons, I believe the higher octane gas will give you a little better performance. I believe the higher octane gas will run cleaner and overall a better gasoline than the lower octanes. For the amount I drive the vette cost difference isn't really that bad. I suppose someone who drives a lot the cost can be a major difference. One thing to be aware of is that you can, on the newer model vettes, put in to high of an octane. One thing the computer does when you first start your car each time is adjust the timing of the engine to where it starts to ping. It gives the computer a threshold to work from base on what type of gas you are using. The car is design to run on lower octane gas and to adjust the timing accordingly to keep it from pinging. So if you put in a VERY high octane gas in the car the computer can't find that upper limit where the car starts to ping. The computer now thinks there is a problem with the car and will set some error code (I don't remember which one). This can drive a you and the mechanic crazy! Put in whatever you think is best, gas is like oil. Some people will swear by synthetics and others say just put in the .89 cent stuff and change it every 3000 miles. ---------------------------------------------------------------------- Rob Loszewski > please cc me your opinions on whether it is damaging > to a TPI motor to run 87 octane in it for let's say, > 75% of its miles. will it do anything other than > reduce power? let's assume it is a "good quality" > 87 octane, passes BMW gas test, or whatever one you want. I wouldn't suggest using a low octane fuel in an engine with TPI. Lower octane fuels have a tendency to carry more particulate contamination than the more expensive ones and the fuel injectors on TPI systems are of poor quality and clog easily. Also, an engine with TPI is categorized as a high output engine. High output engines should at least receive 91 octane in order to extract optimum performance out of them. ---------------------------------------------------------------------- Tony Ozzello when I got my 89 Formula I was told that it preferred the 92 octane stuff but that it was equipped to deal with about anything I fed it. The only real concern is to make sure that you are getting enough detergents run through the motor. The ECM can deal with octane differences no problem. -------------------------------------------- By Ken Mosher submitted by Eric Webb some data about the Sunoco CAM2 fuels from their literature: SUNOCO "Standard" Color......................Purple Research Octane.........115 Motor Octane..............107 R+M/2 ......................111 Specific Gravity........0.725 Reid Vapor Pressure..... 8# -- Distallation temp, degrees F -- Initial............90 10%............160 50%............220 Final...........360 SUNOCO "GT Unleaded" Color......................Natural Research Octane.........105 Motor Octane..............95 R+M/2 ......................100 Specific Gravity........0.760 Reid Vapor Pressure..... 8# -- Distallation temp, degrees F -- Initial............90 10%............150 50%............210 Final...........230 SUNOCO "Supreme" Color......................Blue Research Octane.........116 Motor Octane..............109 R+M/2 ......................112 Specific Gravity........0.715 Reid Vapor Pressure..... 8# -- Distallation temp, degrees F -- Initial............90 10%............155 50%............215 Final...........260 SUNOCO "Maximal" Color......................Red Research Octane.........118 Motor Octane..............115 R+M/2 ......................117 Specific Gravity........0.700 Reid Vapor Pressure..... 6# -- Distallation temp, degrees F -- Initial............100 10%............150 50%............220 Final...........240 And from Rich Lassitter's article in the GS Xtra ... how to mix your own brew: Formula #1 - Toulene ============================= R+M/2.........114 Cost...........$2.50/gal Mixtures with 92 Octane Premium -------------------------------- 10%...........94.2 Octane 20%...........96.4 Octane 30%...........98.6 Octane Notes: Common ingredient in Octane Boosters in a can. 12-16 ounces will only raise octane 2-3 *points*, i.e. from 92 to 92.3. Often costs $3-5 for 12-16 ounces, when it can be purchased for less than $3/gal at chemical supply houses or paint stores. Formula #2 - Xylene ============================= R+M/2.........117 Cost...........$2.75/gal Mixtures with 92 Octane Premium -------------------------------- 10%...........94.5 Octane 20%...........97.0 Octane 30%...........99.5 Octane Notes: Similar to Toulene. 12-16 ounces will only raise octane 2-3 *points*, i.e. from 92 to 92.3. Usually mixed with Toulene and advertised as *race formula*. Formula #3 - Methyl-tertiary-butyl-ether (MTBE) ============================= R+M/2.........118 Cost...........$3.50/gal Mixtures with 92 Octane Premium -------------------------------- 10%...........94.6 Octane 20%...........97.2 Octane 30%...........99.8 Octane Notes: Oxygenate. Very common in octane booster products. Has lower BTU content than toulene or xylene, but oxygenate effect makes the gasoline burn better and produce more energy. Formula #4 - Methanol or Ethanol ============================= R+M/2.........101 Cost...........$0.60 - $1.75/gal Mixtures with 92 Octane Premium -------------------------------- 10%...........94.3 Octane (Methanol) 10%...........94.7 Octane (Ethanol) 20%...........Not Recommended Notes: Methanol is wood alcohol. Ethanol is grain alcohol and found in Gasohol in 10% ratios. Both alcohols are mildly corrosive and will eat gas tank linings, rubber and aluminum if used in excessive ratios. Main ingredient in "Gas Dryers", combine with water. Formula #5 - Isopropyl Alcohol and Tertiary Butyl Alcohol ============================= R+M/2.........101 Cost...........$0.60-$1.50/gal Mixtures with 92 Octane Premium -------------------------------- 10%...........94.5 Octane 20%...........Not Recommended 30%...........Not Recommended Notes: Similar to Methanol/Ethanol. Isopropyl Alcohol is simply rubbing alcohol. How to make your own octane booster (this is the basic formula of one of the popular octane booster products). To make eight 16 ounce bottles (128 oz = 1 gal): 100 oz of toulene for octane boost 25 oz of mineral spirits (cleaning agent) 3 oz of transmission fluid (lubricating agent) This product is advertised as "octane booster with cleaning agent *and* lubricating agent!". Diesel fuel or kerosene can be substituted for mineral spirits and light turbine oil can be substituted for transmission fluid. Color can be added with petroleum dyes. I'll only add one comment regarding using methanol. In a word, don't. It attacks zinc and magnesium very rapidly. Guess what is in carburators and other fuel system parts.