Originally Posted by BRBR549

Oh, I'm a nerd alright. Bad at cocktail parties ... as soon as I start talking, people around me start looking for ways to commit suicide due to boredom.

Originally Posted by BRBR549

Alrighty then, I know this is an old thread, but I just completed my 4.9L EFI to carb conversion on my 1990 F150 Shortbed 5 speed Custom 2wd. I absolutely had to because the thing would stall right at the wrong time (a serious hazard), and THAT was with all new EFI things (including computer, distributor, injectors, blah, blah, blah).
In detail:
1. Weber 32/36 Carburetor adapted to a 86 and pre-EFI manifold. Weber kit from Piercemanifolds.com #K617 (I wanted a K616 manual choke but mistakenly ordered a K617 electric choke. Didn't want the hassle and expense of returning it, so I adapted a manual choke kit to it). The #K616 and #K617 kits have the adapter that fits that old cast iron manifold (with some finagling). I used the original EFI accelerator cable bracket and tack-welded the cable ball joint from the EFI throttle body swing-arm? to the Weber swing arm. Surprisingly that all worked without much pain and anguish. And it has the "original look".
2. Kept the EFI exhaust manifolds - you need to grind off the square-ish casting boss on the rear manifold #4 port, and do some other grinding adjustments to make it fit, but, dang, it worked! Please note that the cast iron grinds REALLY easily.
3. Used a new, Amazon supplied GM HEI one wire distributor made for the FORD 4.9L 6 banger (surprised?). That sucker works BEAUTIFULLY! Powered it with the now under-used EFI relay. Ran the vacuum for it up to the port on the vacuum advance port on the Weber. Set timing to 11 BTDC.
4. Ran the breather to the fitting supplied in the #K617 kit air cleaner simply by shortening the original hose. No air cleaner hassles. Ran the PCV to the old PCV port on the carb manifold. Super clean.
5. Fuel. This was the most difficult sweaty dirty task because I had to remove the fuel tank, and modify the fuel pickup by gutting the EFI fuel pump and adding a take-up hose to reach the bottom of the tank. I had to reinforce the fuel sending unit bracket with an extra holding screw because the original holding bracket was the no-longer-used and no-longer-there plastic fuel pump housing. Put all the back in place and installed a Carter P4070 fuel pump (powered off the old EFI Fuel Pump Relay) forward of the original fuel filter. The pump is self priming, but on first start up it take a LONG TIME to prime. No problem after its primed, but it is noisy (until the wind noise cancels it out at about 25 mph). Ran the fuel supply to a Redline Weber regulator 31800.063 because those Webers will flood with pressures above say 4 psi. Bypassed the EFI Fuel relay ground-through-the-EFI-EEC and took it right to ground - that way the EFI-EEC is OUT of the picture. Fuel sending unit works and the fuel gage works.
6. Removed the old EFI fuel lines forward of the Carter, and removed the old EFI injector harness - a massive birds-nest of wires, but kept track of the oil pressure wire (left side of engine below and behind the distributor) and the water temperature wire (way back of the engine on the lower right). Ran just those two wires back to their sensors after cutting everything else off (literally) and taping the cut ends off). Oil pressure and water temp gages work.

OK, so here are my comments on how well this conversion works. On first start, the timing was way off, but surprisingly the thing started (after the long fuel pump prime). Having set the timing, and learning to work that manual choke, the thing starts WAY FASTER than the EFI ever did. I mean it cold-starts on the first 1/2 of a revolution (that NEVER happened with the EFI). The thing runs beautifully, and at this point, I am realizing no loss of power and no reduction in mileage. No stalling. No missing. Smooth running. Plenty of power. Now look - I am an old geezer (63), and my lead-foot days are past, so I am not running this thing around at WOT all the time. I do realize that the Weber is about 270 cfm and the original Autolite probably did 300 cfm, so there is some de-tuning. But I don't run it at those power levels, ever. If you wanted to, you could probably use a Weber 38/38 and get the 300 cfm if you needed it (or even more).

Drawbacks: There is a lot more lifter/rocker noise making it into the cab, especially at a certain throttle position. Sometimes it sounds like an old Dodge Cummins diesel under full power. I chalk that up to: less things in the way to prevent the sound from getting in there, AND, my old rockers are probably worn a bit much.

So, I have only had this for a few weeks, but overall, I am very happy with this conversion. Reminds me of my days with my 64 F100 and the old 223 - good times. If only I had the three-on-the-tree ...