Can I have Ethyl if she's working?

[Sam]

Wasn't there talk on the forum years ago about A4's ideally needing leaded gas to protect valves from wear. From my view I have always added a couple of oz of "lead substitute" to every tank for the last 40+ yrs full on my 1966 A4 [MMO in the oil] Still running fine. Admittedly I haven't see it on the auto parts store shelf for a while but still have about quart left.

[sastanley]

Avgas most definitely has lead in it. Besides for being 100 octane it is formulated on the assumption it will be sitting around a while before being burned.
Airports USED to have 2 grades, 80 and 100. The 80 octane that had little lead or maybe none. That got discontinued and now 100LL is all there is. "Low Lead" is only in contrast to the old 100/130 or 115/145 octane fuel, it has a LOT of lead in it.
This really sucks for low compression airplanes designed to run on 80 octane.For a while we could run car gas, but then ethanol killed that off and now we have to use 100LL and then add TCP to the gas to prevent lead fouling of spark plugs and sticky valves. TCP is quite toxic, I am always careful handing it.
So the moral of the story is I have to use one toxic chemical to fight the effects of another one because someone had the bright idea to subsidize Big Ag and require corn in gasoline

Joe, I am almost 50, so my first car was a 78 Civic with no catalytic converter and ran leaded gas. When I was driving it in the late 80's, I used to buy the STP lead substitute. My understanding was pre-catalytic (including the A-4) liked the lead to lube the valves and valve stems. I am just asking for clarification on your post. Did the lower octane (for lower compression engines) not have much lead in them, and was it enough for aircraft engines or motors like the A4? Why would they put more lead in the 100 octane fuel?
I was always using a little MMO as my 'lead substitute', until this year when I took Dave Neptune's advice and started adding synthetic 2-stroke oil at about 100:1. That is a guess. I bloop a little bit down the tube before I dump in 5 gallons 87-90 octane E-zero (the octane rating depends on the source.)

[Dave Neptune]

Any kind of lead substitute is a waste of money on an A-4 or any low compression engine. The lead was mainly to "cushion the valve seats" and was only necessary on higher compression engines. As performance increased and compression was raised the lead was necessary to handle the additional valve loads of more duration and lift. The setting of the valves back down on the seats is greatly (stronger valve springs) increased as performance is gained.

The lead also helped in ring wear however the newer metallurgy applied made this a moot point and again the Hi-nickel A-4 block made it unnecessary.

The Hi-nickel block of the A-4 is more than stout enough for this valve seating.
Back when the lead was being removed 'Harder valve seats were sold unnecessarily on low compression low HP engines however anything with HP absolutely needed the harder seats and or the lead substitute.

Dave Neptune

[sastanley]

Thanks, Dave. I never knew why lead was there except that I was told it lubed the valves, and in the 80's when I couldn't buy leaded gas anymore, I tried (as a poor teenager) to remember to put some lead substitute in there when I remembered.
My 1237cc Civic motor made 63HP in 1978. That was probably at 5,500 RPM or so...I don't remember.. With only a 4-speed trans..she spun about 3,300 RPM at 60 MPH. I often drove faster than that trying to beat the gate closing in the high school parking lot in the morning.

[romantic comedy]

Any kind of lead substitute is a waste of money on an A-4 or any low compression engine. The lead was mainly to "cushion the valve seats" and was only necessary on higher compression engines. As performance increased and compression was raised the lead was necessary to handle the additional valve loads of more duration and lift. The setting of the valves back down on the seats is greatly (stronger valve springs) increased as performance is gained.

The lead also helped in ring wear however the newer metallurgy applied made this a moot point and again the Hi-nickel A-4 block made it unnecessary.

The Hi-nickel block of the A-4 is more than stout enough for this valve seating.
Back when the lead was being removed 'Harder valve seats were sold unnecessarily on low compression low HP engines however anything with HP absolutely needed the harder seats and or the lead substitute.

Dave Neptune

Are the valve seats cut right into the block or are they added into the block? I was of the impression that the valve seats are replaceable. (not that it is an easy job)

[Dave Neptune]

Most all valves in the past set right down on the cast iron. The seats are replaceable by boring and pressing in a hardened metal seat like on aluminum heads. Once the lead was being eliminated the manufacturers installed them at the factory. There are many "unleaded" engines manufactured today without the hardened seats but not what you would call performance related engines.

I was learning my engine skills during the time lead was being eliminated. We thought it was the end all for "good motors", but how wrong we were. During those times cars were tuned every 5K miles and valve jobs were done at around 50K miles with leaded fuels and this was the norm. Also during that time there were many garages that just said every motor needs the new valve seats and they made a lot of money doing unnecessary valve seat jobs on the low compression type mild engines and they did not last much longer. And if the new seats were not installed correctly they could come loose and/or recede into to deep of a bore. The really big cammed HIPO engines would sometimes literally hammer the valve deeper into the block until a harder seat was inserted or you kept your foot out of the throttle and kept the RPM's down.

A lot of the wear on the valves was also due to the lack of good engine breathing management as the technology in carbs and mechanical advance systems just could not handle the mix and timing like a modern engine with a computer doing the controlling.

In an A-4 proper valve adjustment will do more for longevity than adding lead a known toxic to humans and all living creatures.

Dave Neptune

[joe_db]

Joe, I am almost 50, so my first car was a 78 Civic with no catalytic converter and ran leaded gas. When I was driving it in the late 80's, I used to buy the STP lead substitute. My understanding was pre-catalytic (including the A-4) liked the lead to lube the valves and valve stems. I am just asking for clarification on your post. Did the lower octane (for lower compression engines) not have much lead in them, and was it enough for aircraft engines or motors like the A4? Why would they put more lead in the 100 octane fuel?
I was always using a little MMO as my 'lead substitute', until this year when I took Dave Neptune's advice and started adding synthetic 2-stroke oil at about 100:1. That is a guess. I bloop a little bit down the tube before I dump in 5 gallons 87-90 octane E-zero (the octane rating depends on the source.)

Some airplanes have low compression engines and are quite happy on 80 octane (87 or so if rated the car way). Some airplanes, mostly supercharged or turbocharged, needed 100/130 octane. (the two numbers are lean and rich octane equivalents)
Someone decided the huge amount of lead in 100/130 was bad for the environment and having 2 grades of gas was a pain, so 100LL got invented. They started with 94 octane unleaded and added enough lead to get to 100. In theory, since it had lower lead than 100/130, it would do fine in all engines. In practice some engines suffer lead fouling to varying degrees. A Cessna Cutlass is so bad it gets lead-fouled taxiing from parking to the runway if you don't taxi leaned way out.

[sastanley]

Interesting Joe, thanks for the info.

Incidentally, my 78 Civic had to have the head rebuilt at about 78K because of burnt valves. I sold it with 165K on it when the daughter came along and needed a four door to get the car seat in more easily.