A couple years ago I bought a '76 F-150 from a junkyard. What i guess had happened, is that the original owner was having trouble with the carb, couldn't get it right, so he just brought it to the junkyard. The body was still real decent, so I brought her home.

From what I understand, the truck had been sitting for over a decade prior to him junking it, so there were many things that needed to be fixed. I went through most of them, and had the carb rebuilt, but it was never quite right. For example, the l/h idle air screw made no difference in idle no matter where it was, while the r/h did. Then, last year, the carb started to develop other issues, so I bought a new carb for it. Problem is, is the new (Tomco) carb is a bit different from the old one, and it's got me a bit concerned (I am no carb guru )

First-the carb has a large vacuum pod hanging off the back, attached to the choke linkage, that the old one didn't have




Second-The old carb, had some kind of plunger assembly in the air horn, behind the choke plate, while the new one does not




Third-the new carb has a few vacuum ports that the old one didn't. Has one right on top by the motorcraft stamping, and another in the rear. Is just plugging these going to be an issue?






Sorry I didn't have a better picture of the truck



Also, I was testing the egr valve, and the results were odd. I hooked a handheld vacuum pump right to the back of the egr valve and pumped it up. It held vacuum, but the valve stem didn't move, even with 25 in vacuum on it, even though the stem moves easily with a screwdriver?

I apologize for asking a bunch of question with my first post

Seemed like every time I had questions with my truck in the past, I would google it, and found tons of information on this site, and it has been a great help to me, in keeping her rolling. Great site guys

-Sam

 

Wow, I am the first one and can answer all of these questions, nice. First off the plunger on the passenger side(new) rear does the same thing that the plunger on the top(old) does, they are choke pull offs, second the port on the back of the carb(new) is for the EGR, third if you apply vacuum to the EGR valve and it does not move it is bad(it is siezed), also the port on the top front of the carb(new), is a vent for the evaporative emmision system, you can probably plug it but if you could utilize it that would be good to, it would need to vent to your charcoal canister

 

Thanks much for the reply man!

After reading what you said, and going back into the garage and looking at the old carb, I feel kind of silly for not realizing that the plunger in the air horn was pushing off the choke, like the pod on the new carb.

The way that my egr valve vacuum is run now, is that it comes off the manifold tree, goes to a temp switch by the t-stat housing, then back through a delay valve, then to the egr valve. I assume it will be fine to leave the egr port on the new carb plugged and leave the egr valve's vacuum ran the way it was? Seeing as the valve does seem to be shot, I called up the parts store, and ordered a new one.

It really wouldn't surprise me, if the way the vacuum lines are ran now, is screwed up though, as they had done some weird things with the vacuum lines before I got it, including hooking the choke stove into the manifold vacuum tree.

In regards to the evap emmisions vent, if my truck came with a charcoal canister, it seems to have been lost to the sands of time, so I'm going to have to try and just plug it.

 

If you replace the EGR valve you do not want it running off manifold vacuum, I would use the ported vacuum port on the back of the darn and plug the manifold port

 

Sure. Being that the port's a little farther away from the temp switch than the manifold tree, it'll be a good opportunity to replace some of the nearly 40 year old vacuum lines anyway