Engine Machining

GordonP said:
I'm rebuilding an engine that has a significantly burnt first cylinder exhaust valve, valve seat, and even the piston is burnt closest to the valve. I had the same problem on my own Model A years ago.

I'm told unleaded gas is tough of the exhaust valves because it burns hotter. I have no data to support this, but the new valves are stainless, and stainless inserts don't burn like the stock block does in my experience.

I have no idea why it's always been the first cylinder. Maybe leaner?
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I fly an airplane with a tank in each wing and valve to control which tank feeds the engine.
The engine is equipped with a cylinder head temperature gauge on each cylinder and an exhaust gas temperature gauge on each cylinder. The engine monitor records those temperatures each second for later download and analysis on my laptop computer. I have flown with auto fuel(unleaded) in one wing and leaded aviation fuel (100LL) in the other. Switching tanks and recording the CHT and EGT I could never discern a difference in those temperatures whether on auto gas or leaded avgas.

Having regular access to leaded fuel I have never seen the need to put it in my Model A.
 
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GPierce, Just curious: Does the auto fuel contain ethanol? (I would think not.) And how high can you fly before "vapor lock" becomes a problem?
 
40 Deluxe said:
GPierce, Just curious: Does the auto fuel contain ethanol? (I would think not.) And how high can you fly before "vapor lock" becomes a problem?
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I’ve flown to 13,000’ on ethanol free fuel but I won’t fly with ethanol adulterated fuel

The FAA does not allow certified aircraft to use fuel adulterated with ethanol.
When I use auto fuel in my airplane it is ethanol free.
Home built aircraft, of which there are thousands flying do use ethanol adulterated fuel. The higher you go the colder it gets so vapor lock isn’t usually a problem. We drive carburetor cars up to 14,000’..
Avgas vapor pressure remains constant at a 6.5-psi level regardless of the time of year or area of the country it is used. Autogas vapor pressure is often changed in some parts of the country from a high of 15 psi to a low of 7 psi. For that reason I wouldn’t use it but many do without apparent problems. 87 octane fuel is only used in aircraft engines up to 7.5:1 compression ratio. Some higher compression engines can use 91 octane ethanol free fuel, mine included but it’s hard to find. Avgas is only available at 100 octane.
 
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GPierce said:
I’ve flown to 13,000’ on ethanol free fuel but I won’t fly with ethanol adulterated fuel

The FAA does not allow certified aircraft to use fuel adulterated with ethanol.
When I use auto fuel in my airplane it is ethanol free.
Home built aircraft, of which there are thousands flying do use ethanol adulterated fuel. The higher you go the colder it gets so vapor lock isn’t usually a problem. We drive carburetor cars up to 14,000’..
Avgas vapor pressure remains constant at a 6.5-psi level regardless of the time of year or area of the country it is used. Autogas vapor pressure is often changed in some parts of the country from a high of 15 psi to a low of 7 psi. For that reason I wouldn’t use it but many do without apparent problems. 87 octane fuel is only used in aircraft engines up to 7.5:1 compression ratio. Some higher compression engines can use 91 octane ethanol free fuel, mine included but it’s hard to find. Avgas is only available at 100 octane.
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Tennessee has MANY more stations than we have around here ... I wish we had 1/2 that many!!



Memphis has 3 stations



one with 91 and



two with 90 octane ethanol free.


https://www.pure-gas.org/index.jsp?stateprov=TN


Just saying ...


Around here if you fly over 12,000 feet you must have an oxygen mask.



At least that was the rule 40 years ago.


I knew dumb guy who flew over Rollins Pass at 11,676ft just to save a little money on oxygen.

I refused to even get into his airplane.


Since it is 11,676 he could sneak in under 12,000!


The joke at the company was that he also lowered the landing gear in case of a down draft!
 
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GPierce said:
I’ve flown to 13,000’ on ethanol free fuel but I won’t fly with ethanol adulterated fuel

The FAA does not allow certified aircraft to use fuel adulterated with ethanol.
When I use auto fuel in my airplane it is ethanol free.
Home built aircraft, of which there are thousands flying do use ethanol adulterated fuel. The higher you go the colder it gets so vapor lock isn’t usually a problem. We drive carburetor cars up to 14,000’..
Avgas vapor pressure remains constant at a 6.5-psi level regardless of the time of year or area of the country it is used. Autogas vapor pressure is often changed in some parts of the country from a high of 15 psi to a low of 7 psi. For that reason I wouldn’t use it but many do without apparent problems. 87 octane fuel is only used in aircraft engines up to 7.5:1 compression ratio. Some higher compression engines can use 91 octane ethanol free fuel, mine included but it’s hard to find. Avgas is only available at 100 octane.
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Thanks for the info! The reason I asked about so-called "vapor lock" was because of the wide variations in auto gas vapor pressure. I remember being at the top of Pike's Peak with a carbureted '86 Chevy Nova (same as Toyota Corolla) and it would not start. A fellow who was patrolling the parking lot with a can of ether starting fluid came over and said "save your battery. You're vapor locked. Common problem up here." It was his job to get people going with the starting fluid. That car had a mechanical fuel pump mounted on the cam cover so it not only heat soaked and had to get the fuel to go uphill but the fuel was now a vapor. Kinda like a flathead Ford with the same high-mounted fuel pump.
 
My airplane is a high wing and gravity fed fuel to the engine like a Model A.
Fuel pump driven engines are more prone to vapor lock as the entry to the fuel pump is low pressure.
I took my my flat head V8 47 Ford coupe over Trail Ridge in 1956, 14,000’ as I remember.
Didn’t have a problem but did later have a problem over the same pass in 58 in a 53 Plymouth.
 
I was at 13,000k density altitude, 10,000 msl. only long enough to get over Solider Pass in the Wasatch to get into the Salt Lake Valley. Not recommended but legal as it was less than 30 minutes.

I dint intend to hijack the thread.
Sorry.
Gilbert
 
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GordonP said:
Can anybody recommend a machine shop in Southern California? I've got some burnt valves in my 29 Coupe and want to put inserts in the block. Probably hone the cylinders at the same time. Thanks
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Gordon,

It's not in Southern California, but you might try Turlock Machine in the Central Valley.They have a good reputation with a lot of the clubs in the Central Valley and Northern California.

David Serrano
 
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