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Leaded fuel For Old Iron


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  #41  
Old 12-27-2007, 02:34:13 AM
Beanscoot Beanscoot is offline
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Default Fuel for old engines

Even for very old engines, Coleman fuel and the like is inadvisable (and costs a lot more than gasoline). Consider that in the Octane rating of fuel, iso-octane is rated at 100, while n-heptane is given a value of 0. On one of my cans of camp fuel, heptane was listed as the only ingredient. With air cooled small engines it is rather hard to hear destructive knocking.
Camp fuel would be good to use as a rinse for an engine going into storage. Warm it up on gasoline, run it dry, then add a little camp fuel and run it out on this. The advantage is that the camp fuel contains no oxygenates nor alkenes, it is a straight alkane fuel which will not produce varnish or gums.


So we should use gasoline in engines, and use camp fuel for its intended purpose- extracting the oil from marijuana leaves.
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  #42  
Old 12-27-2007, 04:58:01 AM
Trashman
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Remember all the talk about valve recession if you use unleaded fuel? The idea was that the tetraethyl lead in pre-1970s era gasoline protected valve seats by depositing a coating of lead, or lead-oxide. Unprotected valve seats eroded away in some engines, a condition known as valve recession, and unleaded gas was blamed.

Frankly, from an engineering point of view it's hard to believe that lead or lead-oxide could coat the valve seats very effectively. Lead is a very low melting point material and could hardly protect steel valve seats in a combustion chamber. Lead-oxide melts at 888 degrees F - higher, but well below combustion chamber temperatures. Oddly enough, the number of valve seat failures in engines using Amoco unleaded gas in the 50s and 60s were no greater than in those using leaded gas, so it logically follows that valve recession was a function of other engine defects and not the type of gasoline used. Most automotive engineers will tell you that valve recession normally occurred as a result of extended high RPM operation or under extreme loads and had little to do with the valve seat material.

Some automotive historians speculate that the valve recession story was mostly hokum pushed by the Tetra-ethyl lead Corporation when they were trying to lobby against the regulations mandating unleaded gas, but you can form your own opinions.

Thanks to all that replied
Chuck
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  #43  
Old 12-27-2007, 05:36:57 AM
Patrick McNallen Patrick McNallen is offline
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Default Re: Leaded fuel For Old Iron

It is my understanding that valve recession happened in automotive engines with cast iron exhaust valve seats that were run on unleaded gas at high output for long periods. The exhaust valves would wear down the seats and "recede" into the head. Eventually, the loss of spring tension and valve train geometry would really mess things up. I have seen a number of Ford 360-390 heads with severe valve recession. They looked like a head that had a hard seat missing. I don't know what residual lead compound prevented valve seat recession, but one or more of them definitely did. This was only a problem in "modern" high compression engines of the late 50s thru about 1970 that were built with cast iron valve seats that depended by design on the lubricating properties of leaded fuel combustion residue to protect the exhaust valve seats. When these engines were run hard on unleaded for extended periods, the valves/seats often didn't hold up. Older engines with hard valve seats were not subject to the problem, and engines with cast iron seats in average service were not supposed to have problems with it no matter how much unleaded fuel they used. Traces of carbon residue supposedly helps protect against valve seat and face wear in any gasoline engine, including those running on unleaded gasoline, but too much carbon or other combustion residue on valve faces will often cause valve burning from guttering.
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  #44  
Old 12-27-2007, 05:45:23 AM
Patrick McNallen Patrick McNallen is offline
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Default Re: Leaded fuel For Old Iron

Who was keeping accurate records of the service life of exhaust valves in engines running exclusively on Amoco unleaded in the 50s?
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Old 12-30-2007, 04:21:15 PM
Beanscoot Beanscoot is offline
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Default Re: Leaded fuel For Old Iron

Referring to my 1949-52 Chrysler shop manual, it shows exhaust seat inserts in the OHV engines. I believe they were Stellite, a very hard nickel / chrome / iron alloy. This seems to imply that unleaded fuel was still anticipated to be used. An old logger I worked for told me as much, that into the fifties there was lots of "regular", meaning no-lead, gasoline sold.
To add to the confusion, valve seat inserts put into auto engines nowadays at rebuild are usually just hardened cast iron, not Stellite. Cast iron is a lot cheaper, and easier to work.
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Old 12-30-2007, 04:24:31 PM
Patrick McNallen Patrick McNallen is offline
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Default Re: Leaded fuel For Old Iron

Many flathead engines had hard valve seats. Most late 50s thru 1971 V8s did not.
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