Swapping out Quadrajet for street demon 625 cfm

[William Miller]

so im trying to switch out my Quadrajet on my 86 c10 for a 625 cfm holly street demon but I’m not sure what the plug is on the top left of the Quadrajet. Is this plug necessary and if so how do I bypass it?

 

[Charlie]

 

[1987 GMC Jimmy]

That’s for the dual capacity accelerator pump. That carb you have there is a 800 CFM casting so your Holley replacement would be an easy downgrade (no offense to you or Holley, which makes a nice carb IMO). I’d work with what you have, and there are professional rebuilders out there that can make that carb brand new for the same or less than the Holley depending if you want a stocker setup or a performance setup. If you’re dead set on the Holley, and you want to sell the Q-Jet as a rebuildable core, let me know.

https://www.crankshaftcoalition.com/wiki/Q-jet_with_dual_capacity_accelerator_pump

 

[William Miller]

GMC Jimmy, I am not very experienced when it come to working on cars and I have zero experience with carbs. I only have the 262 v6 in my truck and I’m looking for a Carb that’s not going to bog dog on the bottom end. Now that said I do like the Quadrajet and I’ve read a lot of really good things about them. Do you think the i should of when with the 750 even though I have the v6?

 

[1987 GMC Jimmy]

No, not at all. The V6’s air needs would have been satisfied with a 475 CFM Economaster would have been sufficient. I think the 625 is better in that case, but that still might be overcarbing it. The Quadrajet only gives you what the engine needs via the air valve rather than being a fixed CFM unit.