3 ms·

Yes, not to mention the lubricant properties of the lead for the valve seats and guides.

by Neil44 5y ago

jabl 5y ago
Hardened materials for poppet valves and seats, like stellite, were invented and used before TEL. It was only after leaded gas became ubiquitous after WWII that manufacturers started saving a buck and stopped using them.
- nate_meurer 5y ago
  Hardened valve seats are useful in racing engines and diesels, but car makers stopped using them in gasoline-fueled road cars simply because they weren't worth the cost regardless of whether the fuel was leaded. Reports of excessive valve seat recession after the phaseout of TEL were all anecdotal, and for every mechanic who swears there was a a rash of worn seats, there are others who say there wasn't. The theory that leaded gas prevents micro-weld induced valve abrasion has not been verified in controlled tests. The final report from the EPA's Valve Seat Recession Working Group found no evidence that leaded gas reduces engine wear under any but the most extreme operating conditions: https://archive.epa.gov/international/air/web/pdf/vsr-finaldraft.pdf https://archive.epa.gov/international/air/web/pdf/vsr-finald... "In real world conditions, virtually no evidence of excessive valve wear has been found in vehicle or engine operation in normal everyday use, and several studies that monitored vehicles in actual daily service in countries that eliminated lead found no excessive valve wear."
deleted 5y ago
[deleted]
nate_meurer 5y ago
This is a myth. Lead has no lubricative value in engines, and in fact causes damage. From https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html https://www.shell.com/business-customers/aviation/aeroshell/...: "The temperature for Lead deposits to form tend to be favourable around the spark plugs (as the whole mixture is quite cool before the flame starts to propagate) and on the exhaust valve stem (as the mixture cools after combustion). The problem is that the deposits are electrically conductive, which shorts out the spark plug - and corrosive, which can start to attack the metal of the valve stems."
- jabl 5y ago
  Late in WWII very high octane 115/145 aviation gasoline (read: lots and lots of TEL) became available for Allied frontline fighters, giving a performance boost. When cruising, pilots had to periodically rush the engines to full power in order to burn off the lead deposits on the spark plugs. And the spark plugs had to be replaced after every flight.
  - nate_meurer 5y ago
    Wow, I didn't know that. The engine in my favorite airplane (Fairchild P-47) had 36 spark plugs. That's a hell of a maintenance requirement.

Yes, not to mention the lubricant properties of the lead for the valve seats and guides.

by Neil44 5y ago

Yes, not to mention the lubricant properties of the lead for the valve seats and guides.

jabl 5y ago

Hardened materials for poppet valves and seats, like stellite, were invented and used before TEL. It was only after leaded gas became ubiquitous after WWII that manufacturers started saving a buck and stopped using them.

nate_meurer 5y ago
Hardened valve seats are useful in racing engines and diesels, but car makers stopped using them in gasoline-fueled road cars simply because they weren't worth the cost regardless of whether the fuel was leaded. Reports of excessive valve seat recession after the phaseout of TEL were all anecdotal, and for every mechanic who swears there was a a rash of worn seats, there are others who say there wasn't. The theory that leaded gas prevents micro-weld induced valve abrasion has not been verified in controlled tests. The final report from the EPA's Valve Seat Recession Working Group found no evidence that leaded gas reduces engine wear under any but the most extreme operating conditions: https://archive.epa.gov/international/air/web/pdf/vsr-finaldraft.pdf https://archive.epa.gov/international/air/web/pdf/vsr-finald... "In real world conditions, virtually no evidence of excessive valve wear has been found in vehicle or engine operation in normal everyday use, and several studies that monitored vehicles in actual daily service in countries that eliminated lead found no excessive valve wear."

deleted 5y ago

[deleted]

nate_meurer 5y ago

This is a myth. Lead has no lubricative value in engines, and in fact causes damage. From https://www.shell.com/business-customers/aviation/aeroshell/knowledge-centre/technical-talk/techart-18-30071600.html https://www.shell.com/business-customers/aviation/aeroshell/...: "The temperature for Lead deposits to form tend to be favourable around the spark plugs (as the whole mixture is quite cool before the flame starts to propagate) and on the exhaust valve stem (as the mixture cools after combustion). The problem is that the deposits are electrically conductive, which shorts out the spark plug - and corrosive, which can start to attack the metal of the valve stems."

jabl 5y ago
Late in WWII very high octane 115/145 aviation gasoline (read: lots and lots of TEL) became available for Allied frontline fighters, giving a performance boost. When cruising, pilots had to periodically rush the engines to full power in order to burn off the lead deposits on the spark plugs. And the spark plugs had to be replaced after every flight.
- nate_meurer 5y ago
  Wow, I didn't know that. The engine in my favorite airplane (Fairchild P-47) had 36 spark plugs. That's a hell of a maintenance requirement.