

The power valve begins opening at the vacuum level stamped on the part. Leaving a gap or clearance at idle will almost certainly cause a stumble. The screw with the spring is supposed to help this too. 015 to prevent bottoming out and bending of the lever.
#Whatsize power valve stock 1850 holley manuals#
The clearance noted in the manuals refers to WOT. There must be no clearance between the arm on the pump and the cam operating lever. One thing that is misunderstood by the new guys regarding Holly carbs is the accelerator pump arrangement.

once the holley is warm they both perform about the same but it can take a lot longer to warm the holley up. my dodge truck starts great and runs pretty good with a 670 holley street avenger on it but the quadrajet on the 350 seems to run the engine smoother all the time even when cold than the holley does until it is warm. i don't know if it would be an option but i have actually been pretty impressed with how good the 350 in my 78 runs with a quadrajet on it. it is the fine tuning of that carb which can be a bit difficult and most shops these days are no longer equipped with knowledgeable enough mechanics to work on carbs. rebuilding a carb is usually pretty simple. to me it almost sounds like the shop that did the work probably didn't know what they were doing if they are suggesting you install a 10.5 power valve especially with the way Holley suggest determining which power valve to use. I would agree that you may want to check accelerator pump adjustment.
