I believe that Joe Curto is correct that gasoline is different, but not
literally leaner - in fact it is less lean.
US Gasoline has a lower vapor pressure than it did in the Sixties,
mainly from reduced butane content. When I worked for a major oil
company blending gasoline we used to add a fair amount of normal butane.
This adds some higher octane to the front end of the boiling range for
gasoline, but more importantly makes it more volatile so it ignites at a
lower temperature. Gasoline also has a reduced aromatic content
[benzene and toluene] so it burns more cleanly, that change would have a
beneficial effect for starting and launching. The oxygenates added
would reduce the flame temperature, so it should run cooler but only
marginally. They also burn more cleanly than hydrocarbons, so less
carbon should be deposited on plugs and combustion chamber surfaces.
They are less volatile than butane, so harder to light. All of these
would affect responsiveness when the engine is cold, but should be
better when it is at normal operating temperature. The absence of
tetraethyl or tetramethyl lead is significant also. If you are in
California, all these changes are more pronounced.
Actually, the clean word is oxygenate.
Glenn C
1959 TR3A TS31684L [in total frame up restoration]
1960 TR3A TS64803L [driving, but needs work]
-----Original Message-----
From: owner-triumphs@autox.team.net
[mailto:owner-triumphs@autox.team.net] On Behalf Of Randall Young
Sent: Thursday, September 18, 2003 2:11 AM
To: triumphs@autox.team.net
Subject: RE: summary: ZS needles?
> I called carb guru Joe Curto, and explained the problem my car was
> having. Basically, hard starting, hard to launch, rough idle,
> hot running.
> I suspected a lean mixture. The plugs read a little lean, too. Joe
was
> not surprised. He claims that gasoline is formulated leaner now,
> than when
> these cars were built.
He's absolutely right, for most of the USA. The dirty word is
'oxygenate',
usually ethanol or MTBE.
> Joe sent me two ZS B1E needles as were originally used in Jags.
Before
> I installed them, I measured their diameter about 1/4" up from the
point,
> and they are .010" skinnier than the stock needles.
Cool tip ! Thanks !
I thought I was going to have to start dressing them down by hand.
Randall
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