I've actually been driving my spitfire a good deal the
past month. But with the colder weather coming and
going (~ 2 weeks ago we were up to high 60's one day
and 30's as a high the next) I'd been using the choke
and leaving it on. Eventually fouling the plugs.
I swapped out the plugs about a week ago, balanced
re-adjusted the carbs, checked the points gap etc. And
the car ran smooth (In fact, it's so smooth now that
when it's still cold, I let the choke out after a few
seconds from start-up and the car will idle smoothly
at <= 500 rpm until it's warmed-up and will idle at
around 900 when fully warm.) No sputtering or hunting
idle.
But I still get a sputtering and loss of power at
3,000 rpms. If I accelerate past it, it goes away. But
if you sit cruising at that RPM, the car sputters more
and more and eventually sounds like the engine is
going to drop off from flooding or air-starvation.
I would just deal with it by not sitting at that
speed, but 1) it's difficult to power past it up hills
(you really don't get good pushed into your seat
acceleration until you hit 3,500 rpm) and 2) traffic
on the road seems to want to keep me doing 45-55 mph
(which is in the 3,000 range) a great deal of the
time.
I have the static advance set to 10 deg. BTDC. on the
low-compression '77 engine that's in the car.
I have the mixture set to about average - 4-5% CO at
idle. I'm using ABT needles in the dual 1.5" SU carbs.
And the stock cam. I have an electric fuel pump and
it's set to around 4-5 psi. And I have a 25D lucas
points dizzy (I think it's from a Midget or early
spit). I've tried using AAU (rich needles) and using
the choke at speed, just to see if it's a mixture
issue, but it doesn't seem to help (it does help
enrich the mixture to help power past the 3,000 rpm
mark though if I give the choke a small tug).
I'm wondering if I'm running out of advance on the
dizzy's vacuum or if the static timing needs to be
adjusted, since I'm not using a stock distributor.
I've used my mity-vac to make sure that the advance
moves with vacuum, but the distributor advance marks
in the books (start/final/range) are gauged in HG
(inches of mercury) not air pressure. And I'm not sure
how you measure the degrees of advance that a vacuum
is giving you on the body of the dizzy(use a
protractor?).
Does anyone on the list in MD have a Mercury vacuum
gauge I can borrow and maybe a foot to depress the
accelerator while I'm over the engine checking the
vacuum readings?
-Terry
Yahoo! Auctions - Buy the things you want at great prices.
http://auctions.yahoo.com/
|