I'm running dual Dellorto DHLA40 carbs on my street/autocross Spitfire, and
am having some troubles. These are quite similar to the Weber DCOE, using
the same manifolds and filters but different jets (which of course have to
be ordered from Europe) - so I'm hoping someone running DCOEs has run into
something like this problem. I swapped from one set to another and found I
had a several of the Thackery spring washers broken. I simply replaced them
with nuts an bolts with lock washers. Now I'm having a hard time getting
the engine revs to drop back down. When I shift, the revs actually climb.
I am using the plastic anti-vibration mounts with the large O Rings front
and back. I put on some new return springs, and the butterflies snap closed
on both carbs. I don't seem to have any air leaks around the manifold to
carb junction. When running the engine without the vent covers on the
carbs, I observe some "splashing" of fuel above the jets. That might be the
source of extra fuel, but I still think I must have to find a source of air
getting through as well.
My question is, "What are the typical symptoms associated with fuel foaming
from vibration of the carbs?" I may not actually be getting foaming, but
simply getting some sloshing around that ends up with extra fuel draining
into the throats of the carbs somehow. I do have another set of thackery
washers, so will probably put those on first and see if the problem goes
away. If it still acts the same way, I'm going to have to pull this set of
carbs off the car and see if I can figure out what is going on. Maybe
someone could point me in the right direction?
I searched the FoT archives because I remembered a short discussion of
thackery spring washers vs. rubber cushion washers. Mark B mentioned using
the rubber washers on the top bolts where they won't get destroyed by
gasoline, and the thackery washers on the bottom mounts. Sounds sensible,
and I'll be doing that when I find a source of rubber washers. Will try
Fastenal tomorrow.
Joe Guinan
Fremont, NE
Spitfires
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