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Discussion Starter · #1 · (Edited)
I have a 19691Mach 1 428 CJ with a fresh restoration.

Fresh rebuild on an original 69 CJ Block bored 30 over with an Edelbrock Aluminum top-end and camshaft.
Bore 4.16, Stroke 3.98,
Head cc 72,
Deck clearance .020,
Piston dish 4cc,
Gasket thickness .030,
Compression ratio 11.0 to 1 approx.

Kit #Performer RPM Cylinder Heads, part # EDL-2044.

The kit came with:
Edelbrock Performer Aluminum RPM Cylinder Heads - 350-60069
RPM Intake Manifold - 350-7105
Edelbrock Performer RPM Hydraulic Camshaft - 350-7106 (.572 lift/296 duration)
MSD 8594 Distributor
Topped off with a Holley 750 Double Pumper Part # 4779-10 3129 (mechanical secondary).
THK 600 five-speed
3.50 gears in the rear
Strange 31 spline axels
Ford 9" Track-Lock

I have less than 1000 miles on this build.

A local engine builder put everything together for me and it runs great, but I'm having difficulty dialing in the carburetor.

It seems to run very rich, especially at idle. I can't find any vacuum leaks. The engine seems to idle fine at 850 RPMs.

I have tried adjusting the fuel mixture with a vacuum gauge and the max vacuum is about 10 in Hg at about 1/2 turn on the idle mixture screws, the engine is not very drivable at this setting. It leans out a little better but seems to stall at low RPMs under load. It runs better at 3/4 turns on the idle screws, but the carburetor runs rich (i.e. smokes at idle, smell fuel, black smoke).

The engine seems to like 3/4 turn on the idle circuit, but the driver doesn't like the black smoke at idle.

Initial timing is set at 14 deg TDC at 850 RPMs and 33 deg @ 2200 RPMs.

I have reviewed comments in multiple forums but haven't seen anything that has helped.

I saw one video published by Norm at Summit Racing. He has a video on Holley Carburetor Performance Tuning, suggesting drilling small holes in the primary throttle plates or adjusting the secondary throat plate position.

It seems Norm likes black smoke.

I want something more streetable. I'm not looking for a race tune right now.

I like old school, but I'm not happy with this tune.
I have been HotRodding for around 40 yrs. I have never seen this kind of problem before.

EFI may be looming in the future.

In this video Norm suggested, drilling 3/32 holes in the throttle plates adjusting the secondary plate open to lean out the fuel mixture?

I could try the secondary plate adjustment.

I have another old-school Holley on the shelf if I'm going to start butchering one by drilling holes in the primaries.

I'm not a fan of the possibility of unspent fuel coming out of the tailpipe or possibly washing the cylinders.

This will be fixed.

Any suggestions or comments are welcome.
 

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Nice to see another 428CJ owner. I have a 70 Mach 1 428CJ car but mine is basically stock with the original carb. Reading what you have laid out the first thing I would do is drop two jet sizes in the primary and secondary and see what you get. I didn't notice you mention the jets hopefully I didn't miss it. But reading through it that is where I would start. Also you are positive you have the bowl floats set properly?

Jake
 

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Discussion Starter · #3 ·
Hi Jake,

Thanks for the reply. That was going to be my next step. I met a guy at a local car meet with an O2 meter setup. We're going to try to change the jetting based on optimum O2 levels.
 

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You will have to weld in a bung into the header or head pipe. But I think that is where you being thwarted. I look forward to hearing what you find.

Jake
 

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Discussion Starter · #5 ·
You will have to weld in a bung into the header or head pipe. But I think that is where you being thwarted. I look forward to hearing what you find.

Jake
I have shorty headers. It might be difficult to weld the bung above the collector flange. Would it be okay to place it slightly below the flange? I have 3' Borla Exhaust.
 

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It depends on the machine your friend has. It will have to be able to take a reading from the exhaust to have any accuracy. A non heated unit element will need to be as close to the collector as possible. A heated collector can be installed several inches downstream from the collector. I would think there would be instructions with his machine with a recommendation. But yeah no matter what you will not install it in the header. It will be after the collector. Have you thought about just pulling 3 or 4 jet sizes and firing it up to see what its like?

Jake
 
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