Power Valve

[Cryo boy]

Hey i run a 350 bored over .60, with a pretty rumpity cam, and i was wandrin... the carbs loadin up, we think it might be a blown power valve, what power valve do i need, its a holly 780 vacume secondary four barrle, on a 350 +.60 wiht a rumpity cam, i have friend that think my car is dying cause of that cam... its pretty wild, so please help, i need to place the order tuesday

[MagicRat]

Whats the carb number? It should be 4 digits on the choke horn, on the top of the carb.
Power valves only vary on the amount of intake manifold vacuum needed to close the valve.
My Holly book shows 2 different valves for your carb; Holly part # 25BP-591A-85 or 25BP-591A-65.

The first one will open (add fuel) with a relatively less throttle opening than the second one.

BTW a 780 carb is a little big for a 350. A 650 might sharpen thrings out a bit.

If its not the power valve, try leaning out the primary jets about 2 points. EVERY aftermarket 4bbl Holley carb is jetted TOO RICH from the factory. Every one, no kidding!! It's as if they expect every carb they build will go right one a 454 with a 6-71 blower.

You should have a #69, 70 or 71 jet in there, so try #67, 68 or 69 jet.

[Cryo boy]

Well, that carb is off of a 396 bb i belive, my dad and his bro were building up a pro street anglia, and that was the carb off it, this happened like 15 years ago. Anyways, i know a guy who has a 650, he wants 50 bucks for it, and this 780 i just rebuilt, when i can scroung together the money for a carb, im going to buy a new one, this carb just hhas to make the motor run for about a month. By the way, thanx.

[Cryo boy]

Part # Opening Vacuum
125-10 1.0" Hg
125-25 2.5" Hg
125-35 3.5" Hg
125-45 4.5" Hg
125-50 5.0" Hg
125-55 5.5" Hg
125-65 6.5" Hg
125-75 7.5" Hg
125-85 8.5" Hg
125-95 9.5" Hg
125-105 10.5" Hg

.....SINGLE-STAGE
.....POWER VALVES - High Flow Part # Opening Vacuum
125-125 2.5" Hg
125-135 3.5" Hg
125-145 4.5" Hg
125-155 5.5" Hg
125-165 6.5" Hg
125-185 8.5" Hg
125-1005 10.5" Hg

.....TWO-STAGE POWER VALVES - Model 4160 Part # 1st Stage Opening 2nd Stage Opening
125-206 12.5" Hg 5.5" Hg
125-207 10.5" Hg 5.0" Hg
125-208 10.5" Hg 5.5" Hg
125-213 11.5" Hg 5.0" Hg

.....TWO-STAGE POWER VALVES - Model 4175 Part # 1st Stage Opening 2nd Stage Opening
125-209 11.0" Hg 6.0" Hg
125-210 9.0" Hg 2.5" Hg
125-211 10.5" Hg 5.5" Hg
125-212 12.0" Hg 6.5" Hg
125-215 10.0" Hg 6.0" Hg
125-216 8.0" Hg 1.5" Hg


I dont see any of the numbers you gave me, do i have to call in the numbers you gave me? Wait whats the opening vacume for the power valve numbers you gave me, I'll just find the closest one.