>Rover 3.5, Carter 500 necked down to 400, Buick intake manifold, mallory
>electronic ignition distributor
Necked down? How? A restirictor plate gives a good vacuum below the plate,
poor above with throttles open. Sadly the carb reads vacuum at its base.
Above the plate. In a Carter low vacuum pops the needles up and the carb
goes RICH. Having been exposed to plates in a racing envirement I can say
avoid them. The AFB is an avs carb anyway. You will not get flow in the
secondarys without enough velocity to open the secondary air valve. The
400 AFB is the best but the 500s will work fine out of the box. Even
better with a few hours and the Carter strip kit.
I use a Carter 500 on my '67 and have used it on others. Also used the the
Edelbrock 500 on a few. Both carbs use the same jets and needles.
The only mod is one step leaner on the needles with one step softer spring.
Lower the float a little. I use a Crower 500230 cam and idle at 550 with
26mpg. The Edelbrock carbs have a very good guide book on tuning.
>
>Rough idle - I tried to turn down the idle yesterday afternoon from 1200
>where it's a little rough running / lumpy, to 800, but it got much rougher
>and coughs and wheezes that low, so I turned it back up to about 1100 where
>it seems to run a bit smoother. I've tried the disconnect one plug at a
>time, and they all seem to be working. My next idea is a vacuum leak.
>Does that seem plausable? I guess it's time to go around spraying WD-40 on
>potential leak sources. Is that the best way to check for vacuum leaks ?
I use an UNLIT propane torch. Crack the valve and move the nozzle around
the gaskets. Any vacuum leak sucks up gas and the idle goes up or down.
This way you do not spray crap all over a clean engine.
>Could it be the cam, which is a bit hotter than stock ?
Idle at 1200 is a lotta cam.
>
>The gas mileage is pretty terrible too, like 15 mpg. I was expecting well
>over 20. I know the 3.9 rear end is causing some of it, but it's much
>worse than I thought it would be.
Sounds rich.
The 3.5 is a very smooth engine, keep tuning, it will work out fine.
Jack Emery
Glenburn Maine
'67 MGB V-8
many others
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