I also had a serious problem with vapor lock and the fuel boiling in the
carb bowls. I know it was boiling because I have a clear filter right
before the carb and in warm to hot weather it would boil away after I
stopped. Also, I had all the usual symptoms.
I solved the problem by first wrapping the fuel line all the way from
the tanks, under the car and up to the carb. That helped some but didn't
solve it completely. Next I installed heat shields on the mufflers (My
apologies, but I don't remember who posted the tip about that on the
list a while back, which is where I got the idea). What completed the
job (no more fuel "percolating" in the carb) was a $5 thin sheet of cork
I got from Ace Hardware. I taped a small sheet of it under the front and
back bowls of my Holley carb. Not especially pretty, but finally, no
more vapor lock and fuel boiling.
Now here's a question for the list that I still haven't figured out. I
think I asked this one before but whatever I've tried hasn't yet worked.
This may also be fuel heat related (so maybe I haven't completely solved
the issue.) I usually have my idle speed set to around 800 RPM. In warm
to hot weather, when the car is at full running temperature (190 to 220
at idle....180-190 at speed, both in 100+ degree weather), when I come
to a stop at a light, etc, idle drops considerably, to maybe 600 or even
500 RPM, and it sometimes stalls. It starts right back up with no
problem but I will have to work the gas pedal to keep it running. It
won't hold that 800 RPM idle on its own. When I take off, it runs great
as usual. After a long run, when I come to a stop if water temp is back
around 180 or less, the problem goes away. I have messed about with the
idle mixture screws repeatedly. Setting them richer or leaner has no
apparent effect on the problem. I checked out my power valve as I was
told this could have the effect I'm talking about. It seems to be in the
range it should be, and I confirmed this with Holley tech support. The
only suggestion Holley had was to try re-adjusting the idle screws,
which I did with no effect on the issue.
By the way, I have calibrated the stock temp gauge pretty accurately so
the numbers above should be close.
So...any additional ideas out there?
Steve Sage
1966 Mk1A, 289, Holly 570 Street Avenger carb (vacuum secondaries).
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