[SuperHart]

You know, I had almost the identical problem with my car, 351W and Holley #4777 650DP carb. Every time I drove the car I ended up smelling like rich exhaust fumes. Nothing I tried helped. Finally I swapped out the 650DP for a #1850 600 vacuum secondary carb and the problem seemed to markedly improve with no change in timing although I felt that performance suffered a little bit. A supposedly knowledgeable engine builder in my area told me that Holley double pumpers always seem to run on the rich side. I have also heard that Demon carbs give noticeably better performance then box stock Holleys too.

I am currently preparing a pair of Holley #8007 390 cfm carbs for use on a home made dual quad manifold for my 351W. I figured even they could be made better so I sent them out to a carb shop for tweaking. I have two friends who both have dual quad setups using the #8007 Holleys and both report that they are getting better performance, better mileage , and cleaner exhaust than with a single Holley of comparable cfm rating. Makes me wonder if the idle circuitry of the Holley DP carbs is the culprit.