How to,properly adjust linkage on 2 4 barrels

Poppas409

Well Known Member
I’m confused on how to adjust the linkage on 2 4s. I assumed, which I now believe was wrong, that you adjust idle on the primary carb only and adjust the linkage so that the secondary carb only opens when you open the secondaries on the primary carb. I believe that is wrong but would someone please clarify for me. And do you recommend the Edelbrock dual quad linkage. Thanks in advance for the info
 

Don Jacks

Well Seasoned Member
Supporting Member 3
The primarys of the secondary carb[frt.carb] must start to open when the rear carb is about 1/3 open for all 8 barrels to be fully open at full throttle if you're setting the linkage up as a progressive linkage system.What carbs.are you using,the original Carters, or the Edelbrocks? If the later,I suspect that Edelbrock linkage would be best.These engines seem to like for both primaries to open at the same time,or what's refered to as direct linkage.
 

Austin Bubbletop

Well Known Member
Supporting Member 1
Not much to add other than I bought the progressive Edelbrock linkage and have it adjusted it to work direct. I just didn't like the response or drivability of the progressive setup. Decent built 409 with a 4 speed. I'd listen to Don.
 

Don Jacks

Well Seasoned Member
Supporting Member 3
If it were mine,I'dd set it up direct.With those eddie's you'll have 4 idle mixture screws to deal with but that's fairly easy.Start by setting all 4 idle screws at 2 turns from lightly seated.Make sure that the idle screws are both adjusted the same.With a vacuum gauge installed as well as a tach,adjust the idle screws.likely inward for the highest vacuum,,highest rpm at an idle.Hook up the vacuum line for the vacuum advance to the drivers side vac.port on the rear carb.Have the vac.advance hooked up during the adjustments.Ebelbrocks instructions may tell you to attach the vac.adv.line to the right [passenger side] port[ported vacuum].Chevrolet engines prefer setting the up the way that I told you.Disreguard Edelbrocks instructions here.
 
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El Rat

Well Known Member
I set mixture and idle on both carbs (same) progressive linkage. It’s pretty easy to try it both ways. I get good mileage and good manners.
 
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