Re: Lead additives

Posted by jdemaris on October 06, 2010 at 09:07:08 from (67.142.130.43):

In Reply to: Re: Lead additives posted by GVSII on October 06, 2010 at 08:17:01:

Some had induction seats even though there were no separate hardened inserts pressed in. Also, there are many other things in fuels that leave protective deposits on valve-seats. Lead is just one of many. Deposits protect seats from recession, but can also cause leaks and valve burning. It's a mix of pros and cons.

Also, just how hard and fast did these old engines get used versus how long they lasted between teardowns ? We used to do many valve jobs, regardless of fuels used.

If you are talking about spark ignition tractors that ran slow, and used very low compression ratios so they could burn alcohol, distillate "tractor fuel", kerosene, gasoline, etc. - you can't compare to more modern engines built late 50s, 60s, etc. that run higher compression ratios, higher RPMs, have hotter combustion chambers, and use gasoline only.

Seems to be many generalities thrown around here, in attempts to prove specific points - and that is illogical (in my opinion).

With any statements I've made, I've attemped to qualify them all and be specific.

Unleaded fuel used in modern gasoline-only engines has been proven to accelerate valve-seat recession when used in extreme HD service when seats are not hard. That is been proven with controlled testing, over and over -mostly overseas where it is a more current issue. Around here in the USA and Canada? Pretty hard to prove from mostly anecdotal reports. How many old gas tractors get used for severe duty? How many are tested with tight controls? If you buy a 1950s tractor, use unleaded, and burn a valve - you're never going to know what really caused it. And, if you do a rebuild along with a valve job, and use unleaded, and the valves recede after 2000 engine hours - you still are not going to know for sure what happened. Might of been some poor valve work, or poor quality aftermarket valve parts, etc. Thus the reason why I'll pay attention to controlled experiments on valve wear only - and pretty much disregard most else.

You of course, are free to believe anything you want.

When this WAS a current issue in the USA and Canada, alternative additives were put into gasoline to offset potential valve-seat wear. So, somebody in North America believed there was a potential problem. Just like now, with all diesel fuel in the USA and Canada getting lube-additives put in -mandated by law to offset premature wear in mechanical injection pumps.

In Europe, those few countries where unleaded gas is a recent thing - gas is getting potassium added to offset wear.

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