428CJ carburetion

[wemooz]

I recently started a thread asking about changing my 2 X 4 carburetors with progressive linkage from 390 Holleys to 600 CFM Holleys. This is on my 428CJ that is very mild (9.65 compression, bored to 433 cubic inches, Crane 343941 cam, MSD). After reviewing the helpful comments, I decided to call the Holley tech line. The bottom line of my conversation was that the Holley guy told me:

1) Using bigger carburetors than the 390s would be too much, and
2) NEVER, NEVER use progressive linkage, which will ruin the engine because it starves some cylinders.

When I mentioned that these engines originally came equipped with 600 or larger carburetors, I was told that essentially the manufacturer did not completely understand carburetion. Then, regarding the progressive linkage, I was told that it was so bad to use that Holley did not offer it for sale.

It seems to me that using linkage that opens both carburetors simultaneously is essentially the same as using a single 780 CFM carburetor, and that it defeats the advantage of having a small venturi at low speeds. Obviously I need more helpful discussion. Incidentally I have run my present setup for 21 years and my engine is not ruined – at least not yet.