Holly, Zenith question..

[d.j. moordigian]

This is a double venturi question that also pertains to the single venturi
style. I have 2 double venturi carbs apart plus a single that I can't get
the secondary well out to study. The question. Why doesn't the double
venturi use a secondary well and the single does? Is it because the signal is stronger in the double and doesn't require the well?

Thanks, Dudley
P.S. Yes, I have Mr. Moller's book and looked at Tom Endy's sight, and
could have missed it.

[Ron in Quincy]

The secondary well is cast into the lower housing of the Double Venturi, both Zenith and Holley. Zenith moved the retaining pin to the front of the lower housing but the undrilled boss is still on the back. The third Zenith Double Venturi is equipted with a brass removable secondary well. Holley went directly from the Double Venturi to the Single Venturi; Holley used several different type casting marks on their lower and upper housings.

It is not uncommon to have to drill out the brass removable secondary well.

Ron

[Ron in Quincy]

fordgarage,

The photo you show is a Double Venturi (main and cap jets in line); I can see a boss on the back and front of the housing; suspect the front only says " ZENITH " as Holley only had the boss and pin on the back side. The correct upper housing for your carb would have a " Z " on the front throat.

The jets that are different in the Double Venturi are the Idle Jet (#10), Compensator Jet ( #18 ), and the Cap Jet which has the orfice at the bottom instead of at the top.

Ron

[d.j. moordigian]

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