Quote:
Originally Posted by Tom Vaught
Cale Johnson thought there should be more "flexibility of transition" with the Holley carbs vs the cam and slot 660/850 center squirter (Tunnel Ram Carbs) and the Vacuum secondary carbs. So he came up with the "johnson Linkage" See Pictures.
1) He designed a PIVOT BOSS on the mainbody of the carbs.
2) he designed a slot and roller profile like the center squirter carbs but the slot went left to right vs up and down.
3) He added a link from the cam part to the secondary lever that opens the secondary blades.
So now the carb had a lot more 'Transition" from just the Primary Barrels to the Secondary Barrels being opened and traveling to WOT.
A very good design but a lot of parts required and EXPENSIVE per carb.
Most people thought it was over-engineered.
So the Later (after Johnson retired) new double pumper carbs using a simpler unique Primary plate and link now use the short rod to activate the opening of the secondary barrels. See last picture.
Tom V.
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Interesting. I see quite a few of the Holley Marine Spreadbores for sale and was thinking how they might be better tuned for transition and off idle responses than automotive aftermarket models given the demands of marine use.