Just wondering if someone could provide a little bit of light on this. I have a 11:1 383, trick flow heads full ported and polished, and Crane Powermax 114051 cam with 1.65 harland sharps. Specs are 112LSA .528 intake .544 exaust and 300 intake and 308 exaust. @ .050 is 238 intake and 246 exaust. Super Victor ported and polished manifold

I have a 750 DP that I just took apart and added the HP main body and proform billet baseplate, it still however has the out of the box powervalve. I am wondering if anyone could give me some advice as to what powervalve they would recommend as a good starting point? The out of the box one? or something less or more?

The car seems to run pretty good but it does seem to be pretty rich at an idle. I have adjusted the 4 corner idle as best as it will get and if I lean it out anymore it will kill the engine right away. As lean as I can get it still has it running rich so I am wondering if maybe the powervalve could be the cause of this? Thanks Guys!

 

check vacuum with a guage and get back to us with it idling in gear, but just my initial gut feeling would be a 4.5 might work, that's what is in my proform carb.

 

I will be sure and do that. I forget what one was in there when I was going though it. Thanks

 

Unless you have the idle set so high that the throttle blades are open enough to bring the main metering system into play, the power valve doesn't have any effect on idle.

The HP body had replaceable air bleeds. If it's too rich at idle, put in larger idle air bleeds.

 

i was under the assumption that if the power valve is open due to lack of vacuum even at idle it will dump more fuel...?

 

The power valve only operates within the main metering system. If fuel is not being drawn through the booster venturi, the power valve can be blown and no extra fuel will be pulled in because the idle circuits are completely separate and below the throttle blades.

 

So if thats the case what would cause it to run so rich at an idle and when you blip the throttle but not when cruising down the road? Stuck needle and seat or something? I know there isn't anything stuck I blew out every orifice and passageway in the carb. I don't have the idle set all that high. I am pretty sure that this cam does have low vacuum I need to locate a vacuum gauge from work and bring it home to check this out. I don't wanna bring this to my work and run the dyno until I get it leaner.

 

Getting the PV right is the right thing to do. But, it isn't causing a rich idle. It could cause a temporary rich condition when blipping the throttle, as you say, if it is opening at too high of a vacuum. You want the PV to richen as you come off idle to prevent an off-idle dead spot, then close during cruise as vacuum comes back up. The blip rich condition could also be caused by the accelerator pump.

But, for rich idle that won't come down with mixture screw adjustment, put in larger idle air bleeds.

 

Hmm well I guess I will swing by the parts store and pick up a pump cam assortment. As for the idle air bleeds this is the first carb I have tuned with those. Are they like another idle mixture deal? Sounds like im having more then one problem at once.

It just seems like right when im getting it to lean out more at an idle it will just die out and not restart until I return the idle screws back to what they were before the adjustment.

 

The fuel that goes into the airstream is a mixture of fuel and air. This helps the fuel vaporize as it enters the intake manifold. The idle mixture screws adjust the amount of air/fuel mix that enters the airstream into the intake manifold. If you are too rich where the engine will run, and it dies when you get it lean enough using the idle mixture screws, then you need to let more air "bleed" into the mixture so you can have the mixture screws turned out more.

The outer air bleeds on the top of the carb are the idle bleeds.