www.barrygrant.com (http://www.barrygrant.com) , this is the best written info I have found on the net or in any book, its the basics but a little better. click on tech info on the at the bottom of the page. There is an interesting part about dual power valve carbs that may cause arguments.

Any drag race carburetor with a secondary power valve must b turned sideways to avoid fuel starvation. The power valve is higher than the jets and is the first to be uncovered as fuel is pushed to the rear of the float bowl. Since there is no way to put an extension on the power valve, the carburetor must be turned sideways to eliminate fuel starvation. That's interesting, I've never really thought about the height of the secondary powervalve and it's relation to fuel location in the secondary float bowl on acceleration. My 850 double pumper has a secondary powervalve. My new 950HP hasn't been apart yet so I don't know if it has one or not. I wonder if something similar to a jet extension could be used to cure the starvation problem.

Your 950HP has a power valve in the secondaries...should be jetted 78's square graemlins/thumbsup.gif

Best bet on the power valve on Holly carb's and for race application is to install a plug and re-jet. graemlins/thumbsup.gif They fail easy, one back fire and complicate the tune-up.

The newer carbs have the pv blowout protection in them...My carb is 3 years old. Not sure if there's any e.t. in removing the rear pv though. My best e.t. was with 80's in the rear,,,december 2002.

Yep you probable right about the ET, just figured it would be easy to tune with them out on a race only car but that may be old information. Did Holley add the protection to all new carbs? I thought I saw it a 950HP ??? Little check valve on the base??? I have not bought a new Holley in years......