Jetting for the 948 and 1275 can be very similar - they both used the same
needles in the SU's in some years. The 1275 gives greater signal at the
jet, thus pulling more fuel, and so the same jetting seems to be ok.
Webers need 2.5# fuel pressure, less than SU's, and less than almost all
electric fuel pumps. But too much fuel would cause it to run rich, at
cruising speeds, and would show up on the plugs. Check float levels, and
check for dirt in the carb - Webers have pretty tiny idle jets that clog
easily, and the car is running on the idle jets when cruising at 60 mph!
main jets come into play at 1/3 throttle or so, and under acceleration.
Brian
At 02:09 PM 27/10/97 -0500, you wrote:
>Hi All
>
>Took Bugeye #1 out for its first extended run since completion of the engine
>rebuild. All driving to this point had been limited to runs of a couple of
>miles or so for tweaking purposes and oil leak checks. Total run ended up
>being about 50 miles. The rest of the club went the full 90 or so. The good
>news is that the engine ran great.....Most of the time. The bad news is that 6
>or 7 times during this 50 or so miles, always while cruising at a constant
>speed (about 60), the engine would start to miss sounding like a plug wire had
>come off. The first time I stopped to check the plug wires and by the time I
>stopped it was running fine again. If I kept driving it would go for a minute
>or two (one time it kept up until I slowed down and pulled over but didn't
>stop) and then start running o.k. again for a few miles. Every time I stopped
>it would be running perfect. I finally gave up and took it home. Pulled the
>plugs and they looked o.k., kind of a light tan on the electrode, not wet or
>oily, but then it was running well for the last three miles. Pulled the
>in-line fuel filter and it seemed o.k. but replaced it anyway. The car has a
>new gastank and new fuel lines except for the metal portion that runs from the
>tank to the engine bay and it was blown out prior to installation of the tank.
> Plug wires, points, condenser, and cap are all new as is the coil. It also
>has a new downdraft Webber. I have never messed with a Webber before and it
>appears that there is only one adjustment screw besides the idle speed
>adjustment. The carb did not come with any instructions on adjustments and
>have not got around to finding a good book on the subject. I just tweaked it
>to where it seemed to idle the best. Any ideas? Any recommendation on the
>Webber book to buy? Could the carb be jetted wrong? These things are sold
>with the 1275 in mind so does the 948 require a larger needle to provide less
>fuel? How about a pressure regulator, should the Weber have one, could the
>fuel pump (new electric) be providing too much pressure? I have a feeling
>this is going to be a tough one because it requires a fairly long run to
>determine if any mods made a difference. Any and all comments will be greatly
>appreciated. This has not been a good week for Spridgets in the Miller
>garage.
>
>Larry Miller
>
>
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