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Old 10-17-2012, 09:11 AM
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leaded 120 octane gas

I just got my old 72 gran torino running. Its got a 351C-2V with an MSD ignition box, long tube headers, an edelbrock performer intake, and a holley 600 carb. I was going to run it at my local drag strip and wanted to run high octane gas in it. The only gas they have at the strip is 120 octane leaded gas. It has the original heads and internals. Can I run leaded gas in it on the strip.

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Old 10-17-2012, 09:14 AM
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whats the concern?
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Old 10-17-2012, 09:18 AM
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I'm concerned that leaded gas may have destructive effects on the engine or the high octane level will burn up the pistons
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Old 10-17-2012, 09:36 AM
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octane does not hurt the engine.regular gas and high octane have the same BTUs.too much lead can foul spark plugs.Im my cessna 172 I had to use 100 octane low lead fuel because 87 low lead is rarely available.The only problem is the cost.I had to clean all 8 plugs every 50 hours of flight time.The lower plugs fouled quicker.
You can mix the fuel,no need for you to run super high octane,and it wont make your car faster if your engine already runs well on pump gas
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Old 10-17-2012, 09:48 AM
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I think you could still get leaded gas in 72. May say unleaded only but its an EPA thing not really an engine problem. But 120 octane may not make as much power as 87.

Octane is the resistance to burn. higher # means it will take a higher temp to ignite. lower will fire off quicker and make more power depending on how your motor is setup. Either way to take any advantage of 120 you will need to change the timing curve a little.

If it runs on pump gas without issue use that at the track. No need to run race fuel unless it knocks. Valve seats should be hard in 72.
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Old 10-17-2012, 10:44 AM
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Thanks for the info. Ill definently give it some thought
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Old 10-17-2012, 12:22 PM
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Quote:
Originally Posted by bubba-21 View Post
I just got my old 72 gran torino running. Its got a 351C-2V with an MSD ignition box, long tube headers, an edelbrock performer intake, and a holley 600 carb. I was going to run it at my local drag strip and wanted to run high octane gas in it. The only gas they have at the strip is 120 octane leaded gas. It has the original heads and internals. Can I run leaded gas in it on the strip.
If this runs fine on unleaded pump gas, leaded high octane would not add anything except lead deposits on the valves and spark-plugs.

Octane has nothing to do with the fuels energy; it is simply a measure of the fuels resistance to self ignition under high temperatures and pressures. The usual problems are detonation and pre-ignition; both of these are highly destructive to pistons and spark-plugs blasting them to pieces or melting them. These conditions, also, result in a massive loss of power when they occur. Compression pressures, RPMs, shape of the combustion chamber and placement of the spark plug, bore diameter, squish/quench clearance, engine operating temperature, intake air temp and mixture temps in the intake track, ignition timing, mixture ratio, vehicle weight and gearing all play heavily on when, where, and if detonation or pre-ignition occur. So there are a multitude of ways to get around the problem should it occur without resulting to 120 octane fuel, high octane fuels are just a quick and dirty (emphasis on dirty) way to deal with the problem.

So if detonation/pre-ignition were to occur certainly 120 octane would delay their onset thus allowing the engine to continue building power but in and of itself it does not make more power than lower octane fuels if they are sufficient to avoid detonation/preignition. This statement assumes the blends of combustible liquids that formulate the fuel are the same. There are small but measurable differences in power output to different manufactures fuel blends but this is a subject hardly ever broached by anyone besides David Vizard. You'll also find that different blends having the same test/research octane ratings exhibit significant changes to the actual octane performance with changes in temperature. Unleaded fuels are much more sensitive to compression pressures and all the other constraints I put into the previous paragraph, since there is no lead additive to boost their performance the blended chemistry of unleaded fuels has to use better root stocks, which is why it is more expensive in like 1970's dollars when both were made in huge quantities and sold side by side for a number of years so a legitimate cost comparison could be made. Today of course the leaded fuels are made in small batches which runs their price way up so today’s cost differential does not show the extra costs of better root stocks used in the unleaded fuels. Besides some of the cost effect on today's leaded fuel can be from starting with un-leaded bases since there's so much of it and just doping it with TELead and the scrubbers that try to keep it from sticking on everything in the engine (bromine and iodine organic detergents so to speak). they help a lot but aren't a total solution to lead everywhere.

Bogie
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Old 10-17-2012, 01:17 PM
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What old Boggie said plus this addition

As valve wear preventive

Tetraethyl lead works as a buffer against microwelds forming between the hot exhaust valves and their seats. Once these valves reopen, the microwelds pull apart and leave the valves with a rough surface that would abrade the seats, leading to valve recession. When lead began to be phased out of motor fuel, the automotive industry began specifying hardened valve seats and upgraded exhaust valve materials to prevent valve recession without lead.
As antiknock agent

An engine requires fuel of sufficient octane rating to prevent uncontrolled combustion known as engine knocking ("knock" or "ping"). Antiknock agents allow the use of higher compression ratios for greater efficiency and peak power. Adding varying amounts of TEL to gasoline allowed easy, inexpensive control of octane ratings; aviation spirits used in WWII reached 150 octane to enable supercharged engines such as the Rolls-Royce Merlin and Griffon to produce 1500 HP at altitude. In military aviation, TEL manipulation allowed a range of different fuels to be tailored for particular flight conditions, and ease and safety of handling.

The use of TEL in gasoline started in the US, while in Europe, alcohol was initially used. The advantages of leaded gasoline — its higher energy content and storage quality — eventually led to a universal switch to leaded fuel. One of the greatest advantages of TEL over other antiknock agents or the use of high-octane blend stocks is the very low concentrations needed. Typical formulations called for 1 part of prepared TEL to 1260 parts untreated gasoline. Competing antiknock agents must be used in greater amounts, often reducing the energy content of the gasoline.

When used as an antiknock agent, ethanol will cause fuel to absorb moisture from the air. Over time fuel humidity can rise, leading to corrosion in fuel lines. Whereas TEL is highly soluble in gasoline, ethanol is poorly soluble and that solubility decreases as fuel humidity increases. Over time, droplets and pools of water can form in the fuel system creating a risk of fuel line icing. High fuel humidity can also enable biological contamination, as certain bacteria can grow on the surface of the water/gasoline interface, forming bacterial mats in the fuel system. TEL's biocidal properties helped prevent fuel contamination and degradation from bacterial growth.

Jester
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Old 10-27-2012, 01:56 PM
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I've noticed that the oil pressure has dropped now and I haven't raced it yet. When I would cold start it before, it would have 60psi of oil pressure, now it has around 25psi the rises to 40psi after it warms up some. I've noticed that I have leaky valve guides too. Is there anyway I can slow the leaks and postpone headwork for a couple months?
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