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Carburetor adjusting problem on reman Holley 750 cfm

6K views 13 replies 5 participants last post by  cdeal28078 
#1 ·
Hi, I am not good at tuning carburetors :oops: . I just bought a holley 4160 750cfm double pumper. Part # Holley 65-80508
This carburetor went on a stock original 1969 ford 429 with 360+ horsepower. Iwent with a little bigger cfm than I needed because I plan on adding on some mods.

Here is the problem, I can't get it to idle to the stock 700 rpm. I turned the idle screw all the way out and it is still at 1500+ rpm for idle. If the idle screw does not work, what do I need to do now? Please help, I don't want to start messing with other screws. :(
 
#10 ·
Sixtyninemercury said:
My choke used to come on at around 1600RPM's. There is a screw that adjusts what Holley calls the "fast idle cam". So with this you can adjust how many RPM's are added to your normal idle RPM speed when the choke is "on".
I think you may have nailed the problem. I found these instruction for my carburetor model. http://www.holley.com/data/Products/Technical/199R9881.pdf
 
#13 ·
Sixtyninemercury said:
514galaxie said:
This thing is a pain to tune. I get a 700 rpm idle at drive. In park, I get an 1000 rpm plus idle. When I shift, the cars wants to die.
How is this carb jetted? What about your discharge nozzles? Have you tuned the (2) air/fuel mixtures screws with a vacuum gauge?
It is stock, I did not touch any mixture screws. I turned the fast cam screw counterclockwise and it lowered the rpms down to 1300 rpm during the cold start warm up. I leaned it out all the way and slowly turned the choke counterclockwise to where it still ran. The choke turned off quicker and I was finally able to set the idle at 700 rpm in park and about 625 rpm in gear.
During the whole process of adjusting I had to take off the carburetor to get to the fast idle cam screw. So what happened is when I went to put it back on , I tightened a nut when something was between the back gasket and the carburetor. I ended up with a hairline crack near the rear bolt hole on my freshly remaned carburetor. Hopefully it doesn't break off during WOT or I'll have fuel everywhere.
 
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