Odd Carb Fuel Mixture Adjustment

[Steve L.]

Hope somebody can help. My 1967 327/300 with powerglide (all stock) with Holley 3810 has a problem with the passenger side mixture adjustment. The highest vacuum and RPM reading occures when the passenger side mixture screw is turned all the way in. The OK driver's side screw ends up about 1-1/2 to 1 turn from seated which is what I expect. The car drives and idles OK, but both sides of the carb are not balanced and I have no more adjustment on the passenger side. My first thought was a vacuum leak near the passenger side somewhere, but the gumout test (sprayed at the gasket interfaces) doesn't increase the RPM and I can't fit a .010 feeler gauge anywhere between the gasket conections. The rear throttle plates are just about fully closed. I set the mixture at about 500 RPM in drive. Prior to this problem I sanded (flat surface & emery cloth) the throttle body flat to remove a heat warp condition (it took three throttle body gaskets to seal before- I would get the LOUD whistle effect vacuum leak if I used less than three gaskets). The sanding removed about .060 in the worst places (near screw connections) in order to achieve the flatness. I also tapped and added the two extra screws which hold the baseplate to the throttle body. I'm also wondering about the stainless foil baffle which sits directly below the carb and above the composition gasket- how can a metal-to metal seal (foil baffle-to-carb baseplate) not likely leak somewhere? Should some type of sealer be used here that wouldn't gum up the carb? I'm trying to keep this original Holley on the car, but I'm running out of ideas. Thanks.

[Clem Z.]

Re: Odd Carb Fuel Mixture Adjustment

check your metering body and mainbody interface for warpage as i find both the surfaces warped on most older holley carbs. also ckeck the throttle body to main body for flatness and seal. if the bottom of the TB was warped then the sealing surface to the main body will be also. the main body can be milled or filed flat but the metering body must be straighten in a jig. try a thin paper gasket between the carb base and the stainless heat shield.