I have a question for all you induction gurus. On a BBC, i am running an Edelbrock Tr2x tunnel ram with twin holley 660s center squirters. The secondaries on the 660s are mechanical and are 1:1. What do you think about running progressive linkage? i want to set it up so that the engine runs on the front carb and the second carb kicks in when i put my foot into. do you think the back cylinders will run to lean?? any tips, knowledge, experience and or suggestions for running a set up like this is greatly appreciated! thanks diego
Probably be better to run off the back first, since the primaries are closer to the center of the intake.
cept he said they are center squirter carbs. I run both full time on a sbc but use Edelbrock carbs. Never had a problem running it that way but it ran like poop on only one carb.
You're probably going to hate the 660s on the street, they ran too rich in the pits even on race cars. I'd recommend swapping them for 650 double pumpers. If you really want to run them, you can modify the linkage on the carb to make it progressive for the secondaries. If you want to run them 1 to 1, and make the throttle linkage progressive, you can run either one as the primary carb, open the second one by 1/4 throttle or so and your distribution will be OK
Your carbs with 1:1 linkage might not be well-suited for use in a progressive setup. Regular progressive 4-barrel carbs might be the way to go here. The rear carb was always used as the primary carb on factory 2 X 4 setups, probably for the reason stated in the post above. I fabricated some progressive linkage on the Pontiac 2 X 4 tunnel ram setup pictured below, carbs are 1966 GTO Carter AFBs (approximately 575 cfm). The primaries on the rear carb start to open first, then the primaries on the front carb start to open. By the time the primaries on both carbs are open an equal amount (about two-thirds open) the secondaries on both carbs start to kick in. Pretty soon all 8 barrels are wide-open. It took a bit of playing around with cardboard templates to find the right pivot points and to get the right opening rates while fabbing the aluminum throttle arms. The end product actuates very smoothly with very little pedal pressure, much less pressure than a factory Pontiac Tri-Power requires.
Don't mean to hijack your thread but i have the same questions about a big block chevy running a tunnel ram but with two carter compe***ion 500 carbs? I also am considering trying progressive linkage. Does it matter if front or back carb is primary carb in a progressive linkage set up? Thanks in advance to anyone who can shed some light on this. I see that some of my questions were already answered while i was slowly typing my question.
This is my main concern about the 660s. I have done a lot of research about this problem and have found a few good sources on tuning them for the street. All of them have said to run some restriction in the main idle feed well. thanks for all the other info guys. Anyone else have anything to add? I am all ears. diego
A manifold with a big plenum like a tunnel ram has is very forgiving about what opens when. I personally would make the rear carb open first like stated above, but the other way should work fine. I ran 2 600 DPs on a 289 on the street mounted sideways with simultaneous linkage and it worked fine and I would do that again. Enderle makes really nice linkage for that. Lotsa cam, so it used all the carb volume. Ford Medium risers w/ 2-4s mounted the carbs backwards and opened the front carb primaries first.
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