Everything is handled by computers today. The old school machinery had to have someone set those things like the choke, or setup the carburetor beforehand, adjust linkage, float height, jetting,...

A choke doesn't really work the way people think. It's not so much "less air", but by closing off the venturi it increases the velocity of the air moving through the carburetor and pulls a lot more fuel in, exactly what's needed.

An old school engine that starts easily in cold weather (without the choke) is not tuned correctly, running pig rich and wastes an amazing amount of fuel. You'll get 'er whipped into shape. It's not just one thing that needs to be fixed, it's a whole bunch of different factors that each need to be brought into line. Ignition timing, good hot spark, and then tune the carburetor carefully.

Do you have a shop manual or MoToRs Repair? Very useful in learning the theory and operation.

 

I do have the shop manual. And I think the timing is right (or very close). A few degrees BTDC and the vacuum advance seems to be working. Spark is there. I have new plugs/wires/coil/rotor/points. Is it hot enough? not sure, the coil was a part from McParts store.

Attaching pic of the weird metal "gasket" piece i was talking about now that i took the carb apart yet again. I was mistaken, it wasn't on the throttle body, it was on the other side of of middle section where Power Valve is.

 

Those "weird" pieces are there to prevent warpage of the carburetor parts from over tightening the screws. Over the years, the carburetor kits and gasket sets for these carburetors have had various thickness gaskets supplied. Anymore, it's hard to find a kit with the correct thickness. Too thick or too thin, are both bad. Warped bowl covers, stripped out threads, etc. are part of the "fun" you run into when working on them.

If it starts, runs, and smells like it's flooding - then it probably is. If you are not sure about the fit of the new power valve and gasket, test the old one for leaks - if it's OK, put it back in with a correct fitting gasket. The fuel leaking around the throttle body means either the power valve is leaking or fuel is dripping down from the main discharge nozzles, either while it's running or just after shutting it off. This will give you the symptoms you describe where you have to leave the choke in, and hold the throttle open to clear the engine while cranking. Any pumping of the pedal will make things worse - just need to hold it open so it takes in air without additional fuel.

I recently had similar symptoms on my Flathead and found that the fuel level was rising due to the needle and seat not sealing off well. When I started seeing the throttle body getting wet after shutting it off, I wasn't sure if the problem was being caused by expansion of the fuel in the bowl due to heat, or if the the needle and seat were leaking. After a few days it got worse and starting dripping fuel from the main nozzles while running. That provided just enough fuel that it would idle perfectly with the mixture screws both all the way in. At that point, I carefully looked into the top of the carb with the engine idling and could see fuel dripping from the nozzles.

Make sure your needle valve seat has the proper gasket and is good and tight using a screwdriver that fits the slot correctly. If your new pump plunger is leather, you should be OK with ethanol gasoline, but the older kits that still had the black "rubber" plunger cups may, or may not work, depending on the material they're made of. I had an older Echlin (NAPA) kit when I last "did" my carb - and the accelerator pump quit working after one day! I thought the pump link must have came off, but it hadn't. The cup had swelled enough that the plunger had stuck at the bottom of the pump well. If you have a blue or green colored "rubber" plunger cup, you should be OK. It doesn't give the stock appearance, but I've always run a good in-line fuel filter between the pump and the carburetor - it helps a lot, especially if you still have the old fuel tank. Mine still has the original, and had been sitting for several years when I bought the truck.

Even though you've installed a lot of new ignition parts, it can be hard to tell about spark quality and intensity by "eyeballing" it . Simple things are easy to overlook. If the point gap is too wide, that will reduce the voltage available to fire the plugs greatly. Poor spark, due to a failing coil, condenser, or other critical ignition part can give symptoms of a "too lean" fuel mixture, miss firing, etc. Often a failing coil will work fine until the engine has been running several minutes, then the available voltage will drop off until the engine will barely run. In the days when most shops had a Sun Scope, it was easy to check the voltage the spark plugs were requiring vs. the voltage the system was capable of producing. The quality of many ignition parts available for older cars nowadays isn't that great, and most are cheaply made imports. If you suspect your coil or condenser may be causing part of your problem - stick the old one back on to see, unless you know a shop that still has an automotive oscilloscope.

I'm wondering what you mean by the leanest setting on the linkage? Are you referring to the shortest stroke setting for the accelerator pump link? Be careful working on that old carburetor. It looks like it's from a car. That's what I have. Here's a picture I took of mine when I had the bowl cover off to replace the needle and seat, set the float level, "fix" gasket leaks, stripped threads, etc. I wish I could be there to help you figure it out! Good luck with it. Sorry this is so long, just wanted to offer some ideas. - Bob

 

It looks like somebody brazed or soldered those shims on the carb base corners, doesn't it?

 

Thanks 52 4x4. Good info for me to know so i know what to look for. My carb is the 7RT, stock for the truck from what I've read.

The old carb parts were over 30 years old and had been sitting for 27 years and useless. The old PV is either stuck or broke and doesn't move, so no chance of reusing. The new carb parts are ethanol ready, the accelerator pump rubber is the blue and it seems to slide nicely (and squirts). However, I've only put non-ethanol in there so far.

I just sanded a few spots that were rough where the carb parts mate together and made sure my seat was screwed in well, and put on the gasket that came with kit (i had been trying another) and tightened the PV. I also readjusted the float slightly. Maybe something I did will help.

I've now disassembled my carb 4 times, and don't even have to look at any instructions anymore, so that's cool! I remember how nervous i was with all the little parts 2 months ago. Not anymore.

 

I just checked the bottom of a spare bowl, and it does have those raised areas. 52 4x4 is correct, those prevent breaking the ears off from overtightening.

 

After fixing carb again and trying to eliminate leaks it started right up and idled well. But I'm back to the under load issue I started with. I used the vacuum gauge inside the cab as i drove, and I'm going from idle 15, cruising around 16-17, down to 4 or 5 inHg when in gear and accelerating under load. Also, I have some pretty good size hills in the neighborhood, so there's no real flat driving. So the 6.5 wrong holed PV in there probably isn't good as I'm probably just dumping a bunch of fuel and wasting gas, I have a 5.5 on the way that has the correct holes. We'll see what that does.

Regardless, my carb just seems worn out, I'm going to buy a used one from ebay and see if it works better, or maybe mix and match parts until I get something that works.

 

Another reason for those "tabs" is to give a higher unit pressure for the critical sealing area of the gasket. If the surface was completely flat, the force would be spread out over a wider area, and the seal wouldn't be as tight.

Brian, I have a spare truck carburetor, a 7RT from a '52 F2. I didn't see the provision for the hand throttle on your throttle body, so assumed yours was a car carburetor. Another thing that's good to check if your carb is still apart, would be for a leaky float. You've probably already done that. If not, there are a couple of things you can do: Shake it to make sure there's no gas inside, check the weight on a gram scale - compare to specs if you can find them, or against the weight of another float. You can also submerge it in a pan of hot water to see if bubbles appear anywhere on the surface, or near soldered joints. If there's a worn depression on the float tab where it contacts the needle valve, it can be dressed down a bit to make sure it has a smooth surface, and won't cause problems maintaining the correct fuel level in the bowl. I set my float level a bit greater than the high end of range shown in the manual. (Be aware too, that the float level specs given in a lot of repair kit instructions aren't completely accurate). As a result, the fuel level in the bowl ends up being lower - and reduces flooding after the engine is shut off in hot weather, due to expansion of the fuel as engine heat rises into the carburetor. (Fuel dripping from the main nozzles is reduced.)
Changing this setting makes the truck a bit "cold blooded" and needs a bit more choke during the warm-up period, but runs fine when warmed up. Just some tips that might help you. It sounds like you're almost there! - Bob

Just missed your latest post. So, what is the truck not doing that you think it should? If you're accelerating under load and climbing hills, the power valve is supposed to be open. Is it missing, not running smooth, down on power ?

 

Carb tuning is very much a cut and try repetitive process. Every change, changes something else. Ignition timing will change engine manifold vacuum, which changes the amount of fuel pulled from a given jet size. Float height/fuel height changes air fuel ratio at cruise. Power valve size is not exactly an OFF/ON switch like proposition - when the engine is in that range of vacuum in. at part throttle that the power valve opens it's going to affect the air fuel ratio, until it opens fully. It's important that the power valve remains fully closed at steady cruise conditions or it will run pig rich and interfere with selecting the proper jet size.

One thing that confuses carb tuning, and distributor timing as well, is that a lot of the info out there is geared towards drag racing. They run full out wide open throttle all the time, and aren't concerned about cruise economy whatsoever. Stepping up in jet size will definitely solve of an off idle hesitation, but the resulting part throttle cruise mixture will be way off the beam and economy will needlessly suffer. I don't know if you've performed a cylinder compression test, but that is the baseline when starting a tuneup. Although 15" of vacuum at 6500' tells me compression is probably very good. You'll get there, just keep plugging away.

 

If you are giving it so much throttle that you're down to 4 - 5 in. vacuum, you should consider downshifting. Not an easy thing with the crashbox, but these are small engines, they need to spin.

 

I read the hand throttle was not on 48-50 models. Also, my float is good, but I have it about in the middle of what the book spec says, about 1.33.

The truck is hesitating under load. Well, not just hesitating, it has no power whatsoever, and vacuum is at or under 5inHg at the time. I barely got back up the hill to my house, and it died when I let off the gas. And then had a hard time starting (flooded, or at least it started when I took oil bath off and then held throttle down for more air). So, you're right. I really don't know what I'm supposed to expect because this is my first carb ever. But, the symptoms are I'm running really rich (smell it and spark plugs black) and so I think I need a smaller number Power Valve so it opens later at lower pressure? I already lowered my main jets from 0.051 to 0.049 (since I'm at 6800ft in altitude here).

 

Tedster, I did compresson testing and I've got 65-75 on all cylinders. Definitely low, but the manual for my altitude says it's only starting to be a problem at around 73, so while the engine is old and tired... I think it's still good.

I could try to re-time, though it's idling well. The problem is now I can't go any further counter clockwise (so I can't check if that helps) as the vacuum advance is hitting the thermostat housing. I'll need to pull out shaft, make a turn clockwise with body to get advance further right... while spinning the rotor to get back where I'm at in the sequence now... but I'm having a hard time visualizing what exactly I need to do to get back where I'm at if I turn the housing. Not sure if this makes sense? Maybe I'm overthinking it?

 

The distributor gear has 11 teeth, so moving it one tooth changes timing 32 deg.

You take off the hold-down, with the distributor cap off, hold the rotor with one hand while you slowly pull the distributor up. When you feel the distributor gear clear the gear on the cam, turn it one tooth CW and push it all back in. You'll need to rotate the body CW also to get back near where you want to be.

 

I did that once, but then couldn't figure out where to put the body relative to the rotor. Do i just line it up with the rotor exactly where it was relative to the body to begin with? That kindof makes sense now that I'm not sitting there in front of the truck trying to do this.

Edit: Logically, the crankshaft hasn't moved, so where you were in the firing sequence shouldn't have changed, so if you have rotor and housing in the same place relative to each other when you rotate the distributor shaft 32 degrees it's still good... If this isn't correct let me know. ha

 

The easiest way to think about it, is there is a firing order for any engine. A certain piston is designated the #1 piston/cylinder. When that piston is at TDC on the compression stroke, both intake and exhaust valves are closed. The balancer/damper "0" mark will (should) be aligned exactly with the damper pointer. The distributor rotor should be aligned with the #1 terminal on the distributor cap. It's a good exercise when trying to troubleshoot engine derangements to start from the beginning and verify the basics. At least it is for me, ha ha.

When I got my slick the distributor was stabbed 180° out, and the steel inertia ring on the damper had slipped about 20° or 25° off axis depending on what day it was. Distributor itself was clapped out with a sticky advance plate. Of course I didn't know any of that, and I wasn't real clear on the concept of ignition timing to begin with, and all that made it very difficult to set ignition timing. Point being don't assume anything when dealing with 50 or 60 year old stuff like this.