> After undersoing the idle nuts ALL THE WAY I couldn't get it to
> idle under 2000rpm...weird. I then squatted doiwn and looked at the throats
> at the same time...the front carb piston was lifted by almost 1/4!!
> I could push it down with my fingers and the car would idle at a much lower
> rpm, I let go...it shot straight back up!
AIR FLOW! AIR FLOW! AIR FLOW!
Do you have a Unisyn?
Set the air flow first! You've got the carbs WAY out of balance
somehow. It could be just a badly worn front carb, but you can't
make the dashpot stick up that high with the air-fuel ratio...
> My hypothesis therefore is that the front carb is screwy
> 1) it would rest at 3/16in above the jet even at idle because it was worn
> which is linked to poor oil damping...
Worn, yes; poor oil damping, I doubt it. You either have the throttle
butterfly too far open or it's got major air leaks.
> i.e. i could push it up and down
> with my finger for 1/4 in withoiut feeling resistance!!
> 2) oil damping was non existent causing a weak mixture when I jabbed my foot
> down...(which makes the piston rise fast with no damping) cured by pulling the
> choke to richen the mixture
> 3) Generally crappy carb tuning because the carbs are so worn
Sad to say, I'd believe that. Do two things first:
- Take your 1/2" wrench and tighten down on all four nuts holding
both SUs to the manifold. Just for grins...
- Squirt carb cleaner (Carburetor Spray-Klene or similar brand)
on the carb bodies, near the throttle shafts. If the idle drops
and the car splutters, there's a leak.
> I tried to remedy the different falling/rising rates by polishing the
> the pistons...but to no avail. The piston wouldn't 'stay down' and I could
> screw the idle screw all the way out and it wouldn't go below 2000rpm. i
> played with the mixture....but this is no way to alter the idle!!!
Ah. Leak, then. Big one.
Again, though, and just for grins, shut off the car and see whether the
front dashpot drops to the bridge. If it doesn't, then you have a
mechanical hangup in the dashpot (or possibly the needle, though your
'74 should have the spring-loaded needles that don't require centering).
But if it does drop all the way to the bridge when the car is off, you
have a leak that's pulling the piston up, as well as buggering your
idle.
> Any aggreements on this? The only thing I wonder about is why it would run
> smothly now and again...piston decides to work...then sticks..then works..
> and so on.
Or a leak that shakes loose... then closes... then shakes loose... then
closes. You could check the manifold nuts too, while you're at it.
--Scott
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