Holley Power Valve Experimentation
I kinda figured theres gotta be people out there that want to run something more than a 10.5 and found a way to make it work. Impossible to find anything posted about what they’ve done that’s for sure. More than one way to skin a cat here. Did you just stretch and drive it watching the gauge and adjust or bench test the valve to get it close first then adjust?
Thanks for posting what you’ve done. I’ve searched and searched the web and your post is (seriously) the first I’ve read of a method with results.
Ive got a tester on the way and will adjust the disc to preload the spring, hopefully see what it yields.
:thumbsup:
I dialed my car to run 12.5 AFR with a dual plane air gap with all plugs burning even and worked backwards to dial in an optimized cruise to drive 50 miles make minor changes and race. I favor my car to run better at the track than cruise. I ran a vacuum gauge to manifold and ported vacuum to see what was going on. The stumble occurred accelerating in 3rd gear on the on ramp to the interstate if I drove like a normal person. If I went up one PJ number the stumble went away but my cruise AFR got to fat. I'm stock stroke 340 with 4.56 gear and gear vendor OD cruise at 3K rpm. I'm sure a stroker would be a different setup due to booster velocity. Everyone needs a different setup with all the variables involved; cid, car weight, carb cfm, rear gear, etc. I run demon metering blocks for a flat fuel curve at the track, 3 hole .025/.025/.026, IFR .032 bottom of block. I did test after spring stretch using an old metering block and the large suction cup with a short hose on my hand pump. I cruise at 15" and needed to have 12" ballpark opening. The 12" worked for me and it also helped passing throttle. Car is very snappy running on just the primaries.
Here's my carb setup and I run at sea level.
PJ 68H 69H
SJ both 86H
IFR .032 bottom block 4 corner idle at 7/8 turn
PVCR .070
Blue cams #1 hole 37/39 nozzles
metering block 3 hole .025/.025/.026
Idle AB .067 all 4 street driving. I change the primaries to .063 at the track to fatten the idle up with my headers uncapped.
Timing is 28* intial 34* total mechanical, vacuum advance on ported and cruise at 48* total.
Many folks make the mistake of changing primary jets when they are actually still running off the idle circuit. Also an open power valve does not flow fuel until fuel flows thru the booster. Engine vacuum at idle will pull fuel thru a blown power valve.
Happy Tuning.
