#21  
Old 10-16-2019, 09:56 AM
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Quote:
Originally Posted by Tom Vaught View Post
Good numbers for the size of the carbs, the cid of the engine, and cast iron #62 heads that maybe go 255-260 when ported well.

The runners are short and have a straight shot at each of the carb venturis/boosters of the dual quad system. Exactly what you want for performance. Carbs like strong booster signals.

I agree that longer runners are better for real street driving rpm points but the typical 4 bbl intakes are at least 1/2 the length (of what they should be for best torque rpm driving). See the picture of a proper longer runner intake on a Performance Engine, notice that the runners are at least twice as long as the typical Pontiac factory 4 bbl intake runners.

Tom V.
Tom you are correct., the heads flowed around 260cfm. A guy by the name of Bill Hughes (older than dirt in the 80's) ported them and the intake when I worked for Jim Kinnett who ran a Pro Stock Hemi.
The more spacer I put on the more it liked it. The Nash T/R was basically out the box but gained .20 just bolting it on with no port work. I sold it to a guy in Mi named Kevin ?? He was big into Pontiacs.

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  #22  
Old 10-16-2019, 10:15 AM
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if it's open to the Exh crossover just drill & tap it for 1/8" pipe, there should be tons of meat there to do that.

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Old 10-16-2019, 10:15 AM
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This motor has #62 heads ported by Paul Spotts and he says the flow around 250cfm.

  #24  
Old 10-16-2019, 10:20 AM
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Quote:
Originally Posted by ITSBACK View Post
This motor has #62 heads ported by Paul Spotts and he says the flow around 250cfm.
What carbs are you planning on running?

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66 GTO Nostalgia Super Stock/Street Legal Car
421 CID, stock block, Wenzler Intake, 2- Carter 750 AFB's, 3.90 Gears, Full Factory Interior, Full Exhaust, Stock Suspension 3750LBS 9.77@136.99
Multiple NSCA/NMCA World Champion

66 GTO 389 3x2, 4 speed, 4.33 gear, Montero Red 33K original Miles
67 GTO 2dr Post, 428, Tri Power, 3.55 Gears
80 Trans Am Black SE Y84 W72 WS6
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Old 10-16-2019, 11:19 AM
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Two Carters, I’ll check the numbers when I get home. I bought this setup already done.

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Old 10-16-2019, 11:23 AM
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I would at least try it. Make sure carbs are jetted properly, correct power piston spring and the linkage is set-up 1:1. If you can fit a small 4 hole spacer even better.

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66 GTO Nostalgia Super Stock/Street Legal Car
421 CID, stock block, Wenzler Intake, 2- Carter 750 AFB's, 3.90 Gears, Full Factory Interior, Full Exhaust, Stock Suspension 3750LBS 9.77@136.99
Multiple NSCA/NMCA World Champion

66 GTO 389 3x2, 4 speed, 4.33 gear, Montero Red 33K original Miles
67 GTO 2dr Post, 428, Tri Power, 3.55 Gears
80 Trans Am Black SE Y84 W72 WS6
  #27  
Old 10-16-2019, 12:23 PM
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I would think for a street car progressive linkage would be better.

  #28  
Old 10-16-2019, 12:40 PM
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You will never get the needed even fuel distribution with that set up if you run them progressive.

What cfm are the Carbs, hopefully not the 750 versions , but the 600's?
The 600s you can run 1 to 1

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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs!
And he was not talking about 1/8 or 1/4 mile ETs!

1) 1940s 100% silver 4 cup tea server set.

Two dry rotted 14 x 10 Micky Thompson slicks.

1) un-mailed in gift coupon from a 1972 box of corn flakes.
Two pairs of brown leather flip flops, never seen more then 2 mph.

Education is what your left with once you forget things!
  #29  
Old 10-16-2019, 12:56 PM
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I’ll check tonight

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Old 10-16-2019, 05:49 PM
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750’s

  #31  
Old 10-16-2019, 06:12 PM
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You can run the 750's 1 to 1. Might need to jet them down a little and pay close attention to the power piston spring. 600's or 625's would be idea if it's a mild engine.

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66 GTO Nostalgia Super Stock/Street Legal Car
421 CID, stock block, Wenzler Intake, 2- Carter 750 AFB's, 3.90 Gears, Full Factory Interior, Full Exhaust, Stock Suspension 3750LBS 9.77@136.99
Multiple NSCA/NMCA World Champion

66 GTO 389 3x2, 4 speed, 4.33 gear, Montero Red 33K original Miles
67 GTO 2dr Post, 428, Tri Power, 3.55 Gears
80 Trans Am Black SE Y84 W72 WS6
  #32  
Old 10-16-2019, 06:47 PM
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Guys,I have been running 2-4s on pontiac since about late 1962.IMO they suck on the street with solid linkage.I dont care if they are 600s or 750s.Im running a set of 421 SD clones on a converted 421 SD "859" intake on my 421 GP right now and a pair of 750 421 SD NASCAR carbs on my 421 with a bathtub intake.I have a 428 RA V engine going on the pump this friday and hope to run a pair of 421 SD 750s on a 2-4 tunnel ram.I will run them solid on the dyno also when the car is raced its switched to solid.The engines have NO issue running off the front 2bbl of the rear carb.FWIW,Tom

  #33  
Old 10-16-2019, 06:52 PM
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There are quite a number of people who have that intake and have had them perform really well. Re the original question the hole is as Tom S first said is there for the air choke. It is ineffectual in that it runs vertically from under the intake straight up to the top where it is shown in the picture - for only an inch or a tad more than that. That is waaaaay too short to get heated air to the choke and make it operate correctly. Factory intakes had a steel tube that fed the heat choke and it ran inside the crossover all the way across to the driver's side, and back, before feeding hot air to the choke. When putting dual quads on the offy intake you need to install an electric choke on the rear carb - or a manual choke. You do not need to plug that hole if it isn't used however since it does nothing.

There are several brands of electric choke on ebay and they all work. Here is the Jegs version.

https://www.ebay.com/itm/Quick-Fuel-...MAAOSwN3ddb37B

  #34  
Old 10-16-2019, 07:06 PM
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I was typing my post #33 above when you guys got into the CFM and progressive vs. static linkage thing. IMO cfm of the carbs should be driven by the cubic inches of the engine. I don't claim to be an expert but I always tell people I'd not put two 750 cfm carbs on anything smaller than a 455 and 600/625 cfm on anything smaller than a 421. But - - I've built several 600 cfm setups for 389s and the buyers were very happy with them; and as we know folks put two 750 cfm carbs on the bathtubs back in the day and those were 421s they were putting them on.

As far as the 1:1 versus progressive linkage thing there are people who feel strongly both ways. I will say that out of the approximately ?? 80 Pontiac dual quad setups I've done for people all but a couple had progressive linkage. Other than bathtubs that is - all of them were 1:1. And why would you want to run a dual quad setup static? 427 Fords, inline Mopars, 409 and early Corvette Chevys all used progressive linkage.

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