return line to gas tank

[Greg Hermann]

>Except for the SUPPLY (suction) side of an egine mouted pump, I have NEVER seen
>in 35 years of working on various cars any demonstrated perk problems...and you
>certainly will not see any at anything close to 40PSI,  we don't with a carb, I
>have never seen even a carb with open vented bowls boil off enough gas even
>sitting in the sun on a 100* summer day after a hard run..to give a problem...
>
>Now on the suction side, yes, that is why I always wind up with an
>electric pump
>i the tank area, pushing forward,  over the years, it just seems more
>reliable....GENE
>--
Maybe you have not been listening, or looking hard enough!

I can point to several things--drag racer's knowing that icing the fuel
helps, Bruce's comment about using a bleed orifice just before a carb's
needle valve, the fact that gasoline is a multi component liquid with a
wide range of boiling points (with the lowest boiling components generally
having the highest resistance to detonation!!), the fact that I personally
have listened to the fuel boil at a pretty good rate in a pair of Weber
two-barrel side draft carbs mounted on an engine with a non cross-flow head
after shutting it off, all the hype (true for a change) that Carter put out
about aThermoquad working better because it kept heat out of the float
bowls, Holley's current hype about zinc (pot metal) being a better carb
material than aluminium because it conducts less heat---and on and on.

Percolation on the pressure side of ANY fuel system is a very REAL thing.
It is just easier to ignore, because its effects are a lot more subtle (not
a go/no go situation) (except for difficulty restarting after a hot soak)
than those caused by suction side vapor!

If you are not after the best possible performance from your engine, fuel
perc problems are probably not worth worrying about in most cases. If you
have not spent enough time/money building your engine (relative to your
means) to care how long it lasts, fuel perc problems are probably not worth
worrying about.

On the other hand, even though you may retard the timing a couple of three
degrees (and lose some performance) and so cure most of the detonation
caused by fuel perc (without giving a care to what is causing it), the
little random episodes of det you still get, (not to mention what fuel cuts
caused by using sloshing in lieu of a fuel gauge will do). even if they do
not melt or hole the pistons, WILL do nasty things like loosen up your top
ring land grooves and pound on your (presumably carefully done) valve
seats. And thus increase your leakdown rate and hurt your air flow, and
lose you a significant amount of performance long before its time!

I would not be here if I did not enjoy working on engines and (as hard as I
try to be cheap) even spending money on them. But working (or spending
money) on any one particular engine to any greater degree than I HAVE to in
order to get my chosen level of performance is not my idea of fun. In fact,
having to do that usually promotes a liberal flow of seriously foul
language!

Think about it!!

Regards, Greg