So have a 950 Proform on my 451. When CP and I first ran this motor it had off idle response the same as a fuel injected car. 2000 miles later it had gone way down in satisfaction mode. It had also been bucking and jumping at about 1500 RPM in 3rd around town where one would be just off idle so had to take the foot off completely or add power which simply made the car accelerate to way over the in town limit. Other issues had seen me put one size smaller primary jets in from the 76 stockers that Proform put in to chase a rich running issue.
A few weeks ago CP and I worked on the low speed air bleeds which made the rich idle way less leaner as we opened them up a little. With the carb tuned for idle I see the screws are only about 1/4 to 1/2 turn out and still some slight rich smell at the exhaust
Have about 9-10"vac at idle which is about right for this cam. Last weekend I replaced the 4.5" power valve with a 3.5" and put the standard pri jets back in and readjusted the primary squirter pump as it had slop in the spring to pump lever. So it runs slightly better with respect to the stumble, accelerates well and has that instant throttle response again. So I have deduced that the idle circuit is set right for neutral idle but does not let enough fuel in (or the FA ratio is not right) in the off idle to throttle transition while in gear in motion. People have told me that these carbs basically always need setting up on the idle bleed circuits only.
So the questions are - in the metering blocks there are small (what looks like jets) for the idle circuits. Are these to meter fuel or air. If they are fuel they need to be smaller, if they are air bleeds they need to be larger to, what I believe, is to cure my problem? Engine has lots of advance, plls one back in the seat at all speeds, but still has black exhausts even after 100mph+ hiway runs.
- Do the idle mixture screws sound like they need to be turned out further?
Appreciate the advice!
