Holley 4BBL lean out

[The_Handier_Man1]

From: Movinyou1  (Original Message)
Sent: 3/25/2005 3:57 AM

Need you thoughts folks. The 4159 on my 413 "flat spots" at cruise speed. If I pull out the manual choke a bit, the condition seems to go away. I want don't know enough about these big Holley's to have any idea where to start looking. I'd like to fix it before my engine leans out and melts. Thanks     Leonard



From: denison
Sent: 3/25/2005 6:01 AM

I am eager to hear any answer to your question also.  I normally just dismantle a carb, clean the passages, and reassemble with all the new parts in from a rebuild kit.  What would a bad/inactive power-valve do on a Holley?



From: DaveVa78Chieftain
Sent: 3/25/2005 12:04 PM

Depends Dave.  Holly power valve is used to enrich the mixture when you bring in the back 2 barrels (transition to all 4 barrels being used).   Does not engauge until vacume drops to around 4 inches.  Failing open would result in a very rich mixture.

The little spring and piston arrangement for the primary jet needle rods on a Thermoquad perform the equivalent function.

When the rear barrels open up, there is a period of time before the vacume seen by them can result in fuel being delivered.  The power valve richens the mixture during that stage (transition) until the hi-speed circuit can start supplying the extra fuel normally.  Power valve can cause a lag (not enough fuel) if not opening; overrich mixture at all speeds if failed open.

Dave



From: Movinyou1
Sent: 3/25/2005 11:11 PM

The carb was rebuilt a couple of years ago. I would imagine anything was possible what with old gas and rusty tanks(at the time) I had to deal with after the rebuild. I was just happy to hear it run. But, it sure threw me with the mixture screws oon the secondaries!      Leonard