340 Intake manifold recommendations

66fs said
That 73 intake has constant EGR ports in the floor. If they are not clogged, they should be closed off. Your TQ base is a 73 340 Manual transmission carb, hopefully the rest of the carb is also. I always ran an Auto carb on an Auto trans, probably no big deal, but they are different. You should get "heavy" out of your mind. If the car is faster and runs better, what does an extra 20 lb matter except for the one time you lay it on the engine. What choke are you running? How in the world can a TQ dissapoint on the top end? When those secondaries open up, it is exhilarating to say the least. Do you have the secondary spring adjusting tool? Are the secondaries opening? Are you using valve springs matched for your camshaft? Most people have no clue about carbs, a good early TQ is still probably the best production carb ever made. Followed by a Q-Jet, but it takes more work to fix them. Another carb most people will tell you are junk. How do those "Stock" and "Super Stock" class cars run so fast with those junk carbs?

I am not worried about the thermoquad having mismatched parts the seller has an excellent reputation on rebuilding thermal quads and this can be shown by the seller's feedback.
Yes I have the thermoquad adjusting tool and I did mess around with the secondaries when I had it on my 318. But I was running it on an air gap with a square bore to spread more adapter which probably didn't help since it's not entirely matched up from the base of the car to the Dual plane setup of the air gap because of the raised spacer. But compared to the air gap with the Edelbrock I noticed a weaker power response with a 318 and I had ended up changing back to the air gap two weeks later. I would make adjustments for the secondaries but I would always have a dead spots at speeds higher than 55 to 60 mph.

As far as valve springs yes I am using the correct valve springs on both the 318 and on my 340 build. The Springs are matched to my camshafts specifications.