running lean and engine damage

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1969dodgedartgt

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Hey guys heres my latest semi-embarrassing/very honest noob question.

About two weeks ago, someone pointed out that I was perhaps running a bit lean. After correcting the problem, my car is idling much better. I've read running lean means running hot which means engine wear.

so a two-three fold question: (answer anyone you can/care to)
1. why does running lean mean running hot? whats the physics behind this at a layman level. (surprised I couldnt find this on the nets, but I havent always been the best searcher)

2. How quickly can running lean damage my engine? my temp gauge was getting to about the 1/3 of the way to the H and I may have driven her for about 4000 miles like this. :angry7: (can I tell if I did damage? ) I'm gona look closely for any metal in oil when I change it soon, any other signs of damage I can look for?

thanks in advance
 
running lean will cause the piston tops to melt quickly. but if it is still running fine, it must have not been too lean.

you should be fine. if it was running too lean, you would of heard it Knocking (fuel knock) whil;e you were driving, and a huge loos of power
 
Running lean raises combustion temps, which in turn raises coolant temps. If you were not experiencing detonation (pinging) than there should be no engine damage. From what you have stated you were not running hot so you should not have been experiencing detonation, at least not for that reason.
 
Running lean is not always a bad thing, just depends on how lean. Years ago I tuned a sport bike I had. Tuned it on the lean side. Tortured that bike for 90k miles set up like that, and never had an issue. I lived in AZ. Bike never overheated, nor did it suffer any type of damage. It was dynoed before I tuned it, made 86 hp. After the tune and new exhaust were put on hit 98 hp. 75k miles later was ran on a dyno one more time, still made 98 hp. Both times it was ran on the dyno after tuning the operators made a comment of it being lean but very strong for a 600cc motor. Bike was lean enough that it popped constantly on deceleration.
 
So how lean was it? You say it idles better. Was it just an external adjustment to the carb? Or did you change jets and/or metering rods?

If you adjusted the mixture screws on the outside of the carb, you really didn't change how rich/lean it was. You just added some air/fuel to the idle. Past 1/4 throttle the idle circuit has no effect on richness. Also, if the idle was lean it would run rough and stall long before any damage occurred (not much load at idle).
 
Lean is more oxygen. The more you have, the hotter the flame. Theres still enuff fuel (Gasoline) to burn, but when the ratio is off, the flame burns hotter. More fuel in the ratio towards rich, less heat.
Heat is power when the chemical conversion takes place from liquid to gas. Some poeple tune the cars via exhaust temp gauges in the header tube to a certain temp AND not as high of as a temp as possible.

Less fuel and/or more air may create more heat, but the balance of the ratio makes less power if it is to lean.
For us street guys, as long as the exhaust isn't puffing black/making your eyes water or nose cringe and/or the best times at the track are achieved.
 
yes it was an external adjustment to the carb... changing mixture screws...
I thought this adjusted the richness throughout the rpm/throttle range.

It had some rough idle, good at times horrible at others. one cold morning it had the worst time remaining started... I thought it was dirty fuel, but I've gone weeks with no idle problems (beside an occasional sputter) after the adjustment so...
 
Those screws up front on the carb are for idle only and there effectiveness on the engine disappear after you get into the primary metering system. This point of activation can be seen as when the throttle plates open up past the slots in the carb and then a tad more.

The more it opens up past that point the less effective they become..and/ the vacuum signal to them diminishes so nothing is really draw out of the idle slots. Your lean/rich running problems seem slight.
 
Have you checked your plugs for a reading, google reading spark plugs, lots of good info out there. In addition you might consider an air fuel ratio gauge.
 
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