Close up of my dual Holley mechanical secondary setup

[427dart]

Just wanted to post a couple of pics of my linkage setup on my Holley 660 and modified 650 with screw in secondary link.
A nice 70 degree day and had the Mustang out for a good run.
This setup goes against the standard of what shouldn't work well....BUT it does!

Giving it a hard half throttle which is just enough to open the other 6 barrels partially, resulted in sticky drag radials breaking loose at speed in 2nd gear with tach instantly hitting 6200 RPM... Big smile on face and no bog what so ever!

I use a slightly modified "Pink' accel pump cam on the front carb that had Vac. Secondary action but now with screw.
Rear carb is of course a modified Holley 4224 center squirt.
Front carb with screw in link


Rear Holley 4224 660 with modified linkage locating plate for increased throttle movement ratio.


Linkage is setup so both carbs throttle plates are full open at end of pedal travel.
There is no hesitation at partial full throttle in 3rd or 4th gear even with the mild 3.50 rear gear!

[levisnteeshirt]

been reading too many 1960's hot rod magazines ? ,, what 650 is that

[GARY C]

I have done that on single VS carbs as a test to see if it would respond to opening faster and if so then I would modify the lighter spring for fast opening.

[427dart]

been reading too many 1960's hot rod magazines ? ,, what 650 is that

Front carb started out as a 1850 series and later I added the 750 throttle plate plus the required venturi cut to blend it in which gives you the 650/660 CFM.
Loved the 60's and 70's! Yes the screw deal normally doesn't work well but it does great with the extended pump shot of the Pink cam plus the squirt action of the 660 in the rear. I had my A/F gauge hooked up to check the mixture and it doesn't overly richen up the A/F ratio.

I did have to slightly reshape the first part of the Pink cam on the front carb to reduce some of the accel shot during first 40% of throttle opening but
then it ramps up as the link hits the screw opening up the secondary.
The linkage is set to slightly open the rear carb first then the front secondary and then all open together.