Carb Swap for my 75 Mark IV

[beaverbikes]

Starting to do my research for this, reading old posts, etc. Any advice would be gratefully received. 30 years ago I came across this basement genius type guy who tuned up this Motorcraft 4350 and it worked well for some years. 20 years ago I tried to deal with it.......man, I was in over my head carbwise. Then my brother tried, he's more advanced at this sort of thing, it ran well but you still had to pour gas down its throat every morning to start her up.

Now I'm wanting to use the car again, two weeks ago she did a 500 mile road trip pulling a heavy trailer- please don't ask about my MPG. Rolls down the road nice and smooth, idles rough, shoot some gas down her throat every morning. This carb HAS to go.

Not sure how good the Edelbrocks actually are, but they sell a bunch of them. Finally, my questions: What all will I need? I studied a 2017 thread by denizen44 about his new Edelbrock intake manifold, but I never understood why he needed it. Because I also see carb adapters for sale. Cheap adapters and more expensive versions. Those new manifolds cost about as much as a new carb, so wouldn't it make sense to try an adapter plate and a new Edelbrock carb? Any other ideas? A different used spreadbore carb that would bolt right on? Not wanting a racecar, just a nice running Lincoln. Thanks!!

[mlj427]

I think on your 75 the carb should just bolt on no adapter needed. If it has a wedge shaped spacer under the stock carb reuse it with a new gasket. And you will need a adapter for the kick down linkage. Edelbrock sells those. If you call Edelbrock they will tell you the products you need I think a 1406 or a 1411 carburetor and the part number for the linkage adapter. I think denizen44 replaced his manifold for improved performance. Good luck

[beaverbikes]

Thanks, mlj. I have a lot more reading to do.

[Lee]

The way you describe the issue with shooting gas on a cold engine…are you sure the choke is closing fully? The external linkage will get sticky over time, and it may not be closing fully, or it may simply need readjustment.

If you pump the accelerator pedal, are you getting visible streams of gas? A bad accelerator pump will cause a lot of problems, including making it more difficult to start (a cold engine also relies on that little shot of gas when you floor the accelerator to set the choke)

The rough idle is just as likely to be due to a piece of carbon stuck in the EGR valve, blocking it partially open, and allowing raw unmodulated exhaust into the intake.

Yes, I am one of the few people on this forum with any love for these carbs. There are a lot of performance issues that are often wrongly blamed on carburetion.

[beaverbikes]

Lee I've been under the hood looking around a lot! I suspect this carb is beyond my abilities. And there ain't nobody else around here gonna do it. But I haven't bought anything else yet. I can't even figure out if the carb has any sort of conventional power valve, without pulling it off and looking. I'm in no real big hurry. Couple weeks ago the car pulled a Hudson Hornet on a trailer pretty well.

[frasern]

Agree with the above, but will add a bit. The 4350 is a spreadbore version of the 4300, not a popular carb, but it can work if set up right, they are finicky, and out of frustration they get blamed for things beyond their scope.
Pouring fuel in after being idle for weeks is not uncommon with todays fuel, however every day is excessive, something is causing the fuel to evaporate. Check that you have an insulating spacer between the carb and manifold, and that it is not cracked, also, there is a baffle under the manifold, part of the gasket, earlier engines did not use it, so someone may have installed early gaskets, without the baffle.
Also, the choke stove is always plugged with rust after all these years, so people back off the choke to compensate. You can clean it out, but an electric choke conversion may be another option. And set your accelerator pump on the longest stroke.
If you elect to swap, an Edelbrock is more user friendly, and your mechanic will not have to learn a new carb. I don't like adaptors, and an earlier or later factory 460 square bore manifold should be available for about a hundred bucks or so at a swap meet or Evil bay. I have one from a '79 truck, but shipping one is costly.

Side note; the 4350 had a factory recall, the secondarys would stick wide open, vacuum would hold them. I had that problem on a '76 truck, back in the day. Only thing I could do was shut it off and restart, finally just wired them closed until I swapped to a Holly and factory steel manifold. Just recently, I found out about that recall, 40 years too late.