Holly Carb tuning / Power valve swap / 427 w/850cfm

[BornWestUSA]

My car is running rich, as in eye watering if you idle it in the garage, but otherwise runs OK.

Ford Racing 427w, Quick Fuel 850 carb. Power valves are 65, and I've learned have zero effect on idle.

11 inches of vacuum at idle after Quick Fuel "wrong/mistake" idle circuit fuel holes below secondary transfer slots blocked off with lead shot.

The idle restriction jets were changed to .035 from .039 also.

Now all 4 corners are adjustable, before blocking the "mistakes" the secondary idle screws did nothing.

The spring was missing on the only (primary side only) power valve "anti backfire" check ball, so I just removed the check ball and seat, so now It's like most double pumpers with wide open vacuum passages to the power valves, it made no sense that it only had a check valve (with no spring) on the primary side.

Now I'm wondering if the timing needs to be changed. I'm running 11 degrees initial, 32 total at 4,000

I could change the springs / limiters in the MSD distributor and run more base timing to still end up at the 32 total Ford recommends.

What are you all running for timing on this set up?200745

[F500guy]

My understanding is the power valve should not be in use until you go for some throttle, do you think it is not operating properly and leaking? How much tuning has been done and is it a new install or just started idling real rich? I have the Holley on my BPE 427 and so far I adjusted the mixture screws to about 1/2 turn open, anything more and it smokes out the garage. I am at sea level and the carb is supposed to be tuned for sea level out of the box. If you are higher, maybe you need new jets. I have not yet driven mine, just played with idle tuning per the holley manual.

[BornWestUSA]

New build / Install

I read the power valve should be 1/2 of the idle vacuum, or 13 inches of vacuum equals a #65 power valve, that is standard?

So just looking for real world examples, still chasing other issues after the first few miles on the road for various state inspections.

[boat737]

A few years back I had a leak in the bowl gasket. When I had it all apart, I wrote down all the stats for my carb. 427w, Holley 750, 3.50:1 gear, 200 foot elevation. HTH.

As for the power valve, 30 years ago, I had a carb'd 540 Mercruiser in a race/performance boat that fractured a power valve due to a backfire. Other than that, the PV should not have any effect at idle.

[BUDFIVE]

Here’s a write up from last August by wbulk. It describes 3 or 4 rich condition causes in the QFT 4150 style (double pumper with 4 idle mix screws) and how to check for them. Very detailed but worth reading.
https://thefactoryfiveforum.com/showthread.php?46900-Fix-That-Rich-Quick-Fuel

[Railroad]

Double check your float levels in both bowls. Look down the venturi while idling. You should not see any fuel dribbling out the venturi or accelerator discharge nozzles.
I guess the engine has always done this?
With a radical cam, you will not get the most efficient burn due to cam timing and lobe overlap, etc.
If you want to raise the idle slightly, it might help for a cleaner burn.
I am surprised you are not getting a higher manifold vacuum reading.
Hopefully you are taking the reading off a manifold source and not the carb.
There are ventrui sources on the carb, not where you want to read.
If the power valve was bad or incorrect, you would probably experience some rough running up to some higher rpm. I think the idle mixture screws are ineffective if the power valve is bad, leaking at idle.
If you have 4 point idle mix screws, check power valves on both ends. Older Holleys had these, do not know about your carb.
Let us know what you find.

[F500guy]

Great Info, Sounds like something I will be looking at this winter.

[BornWestUSA]

What is everybody running for Ignition timing on a 427W ??

[F500guy]

I set mine at 10 deg at idle for my first go around. BPE manual says 8-10, so put it at the max.

[BornWestUSA]

Here’s a write up from last August by wbulk. It describes 3 or 4 rich condition causes in the QFT 4150 style (double pumper with 4 idle mix screws) and how to check for them. Very detailed but worth reading.
https://thefactoryfiveforum.com/showthread.php?46900-Fix-That-Rich-Quick-Fuel

I used the @wbulk write up as a guide.

I blocked the "mistake" idle feed holes below the slots in the secondary. I removed the primary power valve check ball and seat as it was missing the spring.

The secondary power valve had no anti backfire at all, so now the primary and secondary match, neither has a anti backfire installed.

It now responds to idle screw adjustments200835 on all 4 corners, so progress!