[Healeys] Subject: Re: healey overheating and avgas

[Mirek Sharp]

"Mark Schneider"  wrote

" Most Brit cars seem to have a propensity to "run on" or diesel  after 
killing the ignition."

and

"If you have access to aviation gas it works the same way".

I have never had "running on" problems with the few Brit cars I have had, 
including 34 years with a Healey, unless it is out of tune.  I use unleaded 
Sunoco 92,  or 94 when I can get it, and it works just fine.  Bob - if you 
have running on problems you have a timing or mixture issue, or the engine 
is running to hot and your cooling system needs attention.  It is possible 
to get running on caused by a "glowplug" affect in the combustion chamber, 
but I think this is uncommon.   That said, I had a bike where someone had 
used a composite aftermarket gasket which protruded into the combustion 
chamber a wee bit and when I took the head off the thin copper was burned to 
a crisp and was probably igniting the mixture at the wrong time.  A 
correctly fitting gasket fixed the pre-ignition I was getting. I always 
check the fit of the head gasket before installing to ensure it does not 
overlap into the cylinder.

Re Avgas: Someone with more chemistry than me told me that Avgas is 
formulated differently owing to the specific conditions it used for (i.e. 
low RPMs at many thousands of feet ASL.). He suggested that this formulation 
is not necessarily good for car or bike engines.  This is somewhat 
anecdotal, and I know a few guys who run Avgas in motorcycle engines, but I 
have shied away from it.

cheers,

Mirek