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Arch 93
03-10-2002, 07:05 PM
I would appreciate info on lead additives, particularly recommendations about brands. Why do older engines (designed for leaded fuel) sustain damage by running on unleaded?

Thanks

aerog
03-10-2002, 08:01 PM
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Thomas Speer:
I would appreciate info on lead additives, particularly recommendations about brands. Why do older engines (designed for leaded fuel) sustain damage by running on unleaded?

Thanks<hr></blockquote>

That depends on the engine. I'm not sure what brands changed what, and when... i'm sure someone can furnish exact serial numbers for unleaded engines, etc. Essentially, though, if you have a pre-catalytic converter car/engine then you might (probably?) have an engine/head designed for leaded fuels.

Some engines, like VW aircooled engines, have valve guides and seats that don't require lead but may require higher octane fuels than originally called for.

In the UK you can take your chances with LRP (lead replacement petrol), which uses potassium as a lead-additive rather than the TEL lead additives. I thought that was neat until I found out that valve-guide wear had increased to terminal levels in some engines that were switched to LRP, along with other problems.

In the states there is, apparently, a product called "relead" which should do the trick for a short-term solution. The problem is, with any "leaded" engine that is run on unleaded (with or without additives) valve guide and seat wear will swiftly become terminal - particularly at highway speeds for extended periods. Additives will slow the effects of the guide/seat wear, but supposedly won't stop it forever.

The end solution to the lead problem is to pull the head off the engine, have new valve guides and seats installed (or just replace the head) - which will provide a permanent solution with unleaded-compatable materials.

Incidentally, some folks will use 100LL (100 Low Lead) Aviation fuel in older cars. I see them all the time at the airport filling up - usually older hotrods that haven't been converted, etc. I guess it works, but whether it's good or bad I have no idea.

Update: Check this web site: https://www.chicagolandmgclub.com/techtips/540.html

[ 03-10-2002: Message edited by: aerog ]</p>