340 Intake manifold recommendations

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For the cam used, here's another vote for the factory TQ and intake. You just can't beat it. I had a 73 340 back in the day. Typical punk kid, thought I'd put on an early 340 square bore manifold and run a Holley. I went slower. Put the intake and TQ back on and resumed kicking ***.....
 
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?
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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.
 
Do you know what secondary jets you are running? I've never had any dead spots, from 273 to 340 to 383. The 383 used a HP 400 TQ, while the 273 and 340 ran a 71 340 TQ. You just floor it and hold on.
 
Here are notes I have from the seller when I bought it.
Looks like the setup it has currently is listed on the bottom left. The extra parts I have are listed on the lower right.

20230429_105737.jpg
 
This alum Mopar Performance version of the 1968 /340 intake rocks!!!! They hard to find but worth the coin...

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TQ 6318 1973 340 manual trans

primary jets = 120-4098
secondary jets = 5137
Rods = 75-1962 (.067 x .055 x .045)
 
Also agree the stock TQ intake is very good, on a par with the Perf.
 
I have swapped from an air gap manifold to a victor 340 on my 410 but have also swapped to a slightly larger cam ( howards hyd roller custom 238/242 610 lift on a 112 l/seperation and from edelbrock slightly ported heads to trick flow heads.
I have lost low end hp on the chassis dyno but pulled 35 hp on the top end to 425 rwhp. After studying the dyno sheets I noticed the bottom end were it had lost torque it was lean and when the air fuel ratio recovered it rocketed past the old graph. I felt that it was not fully warm when he did the run and since I have gone up jet sizes on the primaries. On the road it does not feel any loss of torque as if you hit the throttle in second gear at about 2ooo rpm it goes sideways with wheelspin straight to about 6500 rpm. ( five speed manual TKO600) I have also noticed if you do the same when it is not fully warmed up it just falls on its face until the revs come up. When you have a 410 properly tuned how much bottom end torque do you need in an A body weighing 2900 lbs with driver. My car an Aussie VJ Valiant Charger has gone 11.4 with the old set up so expect the new set up to go low elevens
 
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