Posts: 942
Threads: 154
Joined: Jul 2000
Have an out of the box 750 Double Pumper.
I cannot get it to lean out for the life of me
440 4 spd with 10-11 of vacuum at idle (very irradtic very hard to pin point exactly)
I went down to a 4.5 power valve from a 6.5 and a 73 jet in the primary to a 68 (I do understand that they aren't factors at idle, just mentioning the changes)
The 4 corner idle, I can bring 3 of the 4 all the way close and it still runs.
It will still run with the front 2 closed
I started at the 1.5 turns on all of them and little to no change in vacuum
could it be a defective carb?
I checked everywhere for vacuum leaks, there are none I can detect
thoughts?
Posts: 6,798
Threads: 474
Joined: Jan 2013
Just an idea but is fuel psi good for that carb.?
The Idaho Andy
OL Blue is scared of Max
Posts: 942
Threads: 154
Joined: Jul 2000
Set at 5-6 Psi Holley Blue Top with regulator
Posts: 4,336
Threads: 91
Joined: Jan 2013
Are you sure the throttle plates are closed?
Is this a bad time to tell you how to fix a Holley for good?
...replace it with a Carter! LOL
What car is this in?
President, New England chapter of Coronetaholics anonomous.
Posts: 942
Threads: 154
Joined: Jul 2000
The 4 speed Rich
I've had very good luck with the Holleys in the past, this one is stumping me a bit.
Tried tweaking the plate and its still not having an affect
The cam may have something to do with it of course, I think its a big overlap as well the car likes a lot of initial timing
The 850 I had on there ran extremely well (albeit always burning rich) but I wanted something a little tamer so I don't smell like and exhaust pipe when I get out of the car!
Posts: 137
Threads: 19
Joined: Jul 2013
Are the float levels set ok? Sounds like you have covered everything else well?
Posts: 942
Threads: 154
Joined: Jul 2000
Yes Sir, just trickling out of the site plug when you give it a bump
Posts: 942
Threads: 154
Joined: Jul 2000
Everything I am reading seems to point to opening up the secondary throttle plate, I think I need to revisit that setting (open it more) and give it a whirl
Posts: 435
Threads: 13
Joined: Jan 2013
Throttle plates could too far open. Sounds like it could be drawing fuel from the transfer slots at idle making the mixture screws ineffective. Are there holes in the throttle plates? I've had luck with drilling 1/8 holes in the throttle plates to allow more air go thru the plates instead of around them.
Posts: 1,509
Threads: 68
Joined: Jan 2013
I went thru this same senario with my car - the ultimate fix was a locked distributor. It sounds like your problem could be the low vacuum - if the carb is old and worn it will need even MORE vacuum to work correctly. Unfortunately - you will need a start retard if you run a locked distributor and probably have to shut off the engine in gear to prevent run-on.
