Thu, 13 Jun 96 19:39:58 +0200, Phil Bates wrote:
I recently moved from PA to Idaho. Now my 67 MGB runs hot. I was
thinking it may be due to the elevation (now at 4350 ft), but that
should make me run rich, not lean.
>Phil, I was of the opinion that this is just the great advantage of
>SU carbs over normal, fixed jet ones, such as WEBER carbs. SU carbs
>deliver their mixture caused by the pressure differential between
>the inlet manifold-pressure and the outside pressure. The outside
>(absolute) pressure decreases with altitude, (almost?) linear with
>the air density. The pressure diff remains constant and this causes
>the fuel/air mixture to be the same at altitude.
Also, I am considering running some 100LL (100 octane, low lead ....
aviation fuel). Would this make my car run hotter or colder? The
guy at the local small airport doesn't have any issues with selling
me the fuel (legally at least), but he was very concerned about what
it might do to my engine. The big concern was "detonation." He said
he would not be responsible for damage done to the engine. Anyone
know if these concerns are founded?
>The octane number sez it all. You certainly won't have a problem
>with detonation with this high octane number. Low Lead is added (I
>mean the words: Low Lead!) in the 60's to aviation gasolines
>(AVGAS), because before that date AVGAS contained an awful lot of
>lead. At present, the amount of lead in AVGAS 100LL compared to
>leaded premium gasoline, as sold - but lot for long anymore - in the
>Netherlands, is still very high.
>I think this fuel will certainly not harm your engine and I agree
>with most of the list that lead was originally added to >increase
>the octane number of the fuel. As a mere coincidence it was found
>out that the lead debris on the valves and seats caused a
>lubricating effect. However, I'am informed that if you fill up your
>tank once in three fillings with leaded gasoline this effect will
>take care of your valves adequately.
>I recall a thread about using unleaded gasoline in an MGB engine
>without an 'unleaded head'. There was a chance that your valves
>would get burnt in the end, say after 100,000 miles or so, but
>possibly not before your engine needed a rebuilt anyway. (Retoric
>question: Is this really true? Why am I putting expensive leaded
>gasoline in my MGB?)
Bert Otten
'67 MGB (DM-19-49)
|