Jerry -
Regardless of the tune of your engine build and the needles in the
carb, you should always be able to adjust the idle on HD8 carbs to
factory spec ~ 600 rpm. The problem isn't your carb needles.
I suspect either:
1) Your throttle valve plates are not seated properly. They should be
fully closed at idle and if not seated properly in the throttle body
then you will have air leakage and too fast of an idle. Take the carbs
off and check that they seat fully in the throttle body
2) The slow idle screw (the big screw) o ring is worn out and air is
leaking past the o ring causing fast idle
3) You have a vacuum leak somewhere
Once you have all this sorted, you should be able to adjust idle
properly. Than and only then should you start thinking about needles.
Alan
On 10/7/08, Jerry Costanzo <grumpyinloomis@ssctv.net> wrote:
> I have installed my HD8 carburetors onto a slightly modified BJ8 engine.
> The
> carburetors were rebuilt (by me). At present, the engine runs well but the
> carburetors have a little backfire when cold and occasionally when warm.
> They
> test by lifting the piston to be too lean. If I adjust the fuel mixture any
> richer, the idle goes over 1100rpms and I still don't get the lift test to
> properly keep the rpms steady.
> Other items of note:
>
> Checked for vacume leaks. Did not find any with a unlit propane torch.
> Timing appears to be correct. I went back and checked the valve positions
> vs.
> cylinders at top.
> Engine revs ok, I have not driven the car to test the power. It does not
> have body panels on yet.
>
> Is it time to try a richer needle in the carburetor? If so, which would
> you
> try?
>
> Jerry
> BJ8 in progress
> BN4
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--
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Alan
'52 A90
'53 BN1
'64 BJ8
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