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Okay, you know I get horrible mileage and many of you suspect carb problems. I continually insist that my carbs are tight around the throttleshafts and that the mixture seems right because the idle behaves properly when the lift pin/screwdriver test is tried. I get no clouds of smoke or lean pops, but the mileage continues to be poor, my sparks often look sooty and and it takes a lot of warming before the car accelerates properly from a stop.
I've ordered a new electronic ignition setup but it is has been delayed for a couple weeks. I've also just reinstalled the proper B18B head on the engine. Lets consider the whole engine setup thing back to the original baseline.
I have some more carb questions.
I just picked up a new carb SU HS6 rebuild kit (officially for a P1800S).
It includes everything but the throttle shafts and throttle plates.
1) Metering Needles
The kit has some new ZH needles but my carbs all have KN needles. According to my Haynes SU carb book, KN's are proper for a 1968 B18B and ZHs needles were found on several models up through the 1967 Snow Weasel. Is one of these better for fuel economy? How do they differ? My manual calls them all "standard"
2) Jets.
My kit has a new red-collar jet and new yellow-collar jet. Closer inspection shows that they both point the same direction. They are both look to be right-hand jets. Will they work on either side? Which color goes to which carb?
3) Grosse Jets
Yeah I know some of you hate them, but these are not the brass-pin type, they are the real ball-bearing models and I've never tried them before. They are widely recommended for the British cars. Is it worth a shot to try them?
4) Throttle Plate Seal.
I've had several sets of SU's apart lately and in the course of carefully fitting the throttle shaft and throttle plate I've found that the plate does not seem to fully and completely seal on the sides. This is odd because the plate moves smoothly and comes to a complete rest against the top and bottom of the housing, but if I hold it up to the light with the plate completely closed, I can see a narrow crescent of light along the edges. No amount of plate adjustment or even changing plates seems to get this area to seal completely.
This is the case with all three pairs of HS6s that I have - both 2-bolt and 3-bolt types. Is this normal? Does it indicate wear - there does not seem to be any obvious wear to the throttle tunnels.
5) Two-bolt or three-bolt?
Aside from the size and shape of the air-filter, I do not know of any significant differences between these two types of carbs. I've had both types completely disassembled and re-assembled. Is one better than another for a rebuild? I'm leaning towards burning my rebuild kit on a two-bolt set that I successfully re-bushed and that has a vacuum fitting for a vac-dizzy. I also carefully re-bushed this set and the throttle shaft have almost zero detectable shaft play (well one if tight with no movement at all, while another has a *slight* wiggle. Better than they were, that's for sure.
Anyway, any thoughts or advice here would save me wasting some hard to find seals on a pointless rebuild.
Thanks as always.
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