292 straight 6-Exhaust manifold and vacuum line questions

[thefarmboy21]

To give you some background info, I've got an 86 K20, with a 292 4-speed. It only has 82,000 original miles, but it's been an old mans farm truck it's whole life.

Recently I decided to rebuild the carb and toss all the smog junk, because it was getting 7mpg, barely pulling out of its tracks and backfiring a lot. Plus the bearings in the smog pump were shot and it just SQUALLS something awful and the inside of the carb looked like it was coated with tar.

So now to my questions:
1. On the intake manifold is mounted a little metal can/valve that has a vacuum port on it (1/4" or so) and it has a rod that runs down and works something in the exhaust manifold I think. What is it, what vacuum port should I hook it to and DO I EVEN NEED IT?

2. What vacuum lines do I really even need. As far as I can tell, all I need is distributor advance, brake booster and a pcv valve....that about right?

3. The line that runs to the fuel tank, formerly was in the vacuum canister...just leave that open like a regular vent tube?

4. What runs my heater flap and if it's a vacuum line where does it go?

5. I have two grommets in my valve cover....if I run a pcv valve, do I want a vent cap in the other or a plug or does it matter? First I thought vent cap to circulate more air but thought it may be the same as a vacuum leak?

I think that's all for now. Thanks in advance. I'll try to go look at my 77 K10 tomorrow for a guide so to speak, but it has a 350 and I'm not sure if it has an egr system or not. I just want my 86 to be as SIMPLE as possible under the hood.

[thefarmboy21]

Can anyone with a 292 or even a book, at least tell me what the vacuum canister on the manifold is??? I would've thought it was the EGR, but it's behind the carb mounted onto the intake manifold VS google pictures with it mouted in the front and on the side of the exhaust manifold. Also it has a linkage rod that runs down to something on the backside of the exhaust manifold??? I just need to know what it is, what it's for and if I can take it off! Thanks.

[bd]

EFE valve - a vacuum operated heat riser to warm the intake for better atomization of fuel during cold starts.  Refer to the 1986 Service Manual emissions section 6E, beginning on page 860.

The PCV system needs to breathe, so the 'second valve cover grommet' needs to be vented to the air cleaner or a vent that provides filtered air.

If you eliminate the fuel tank vent line through the vapor canister, you will probably increase fuel odor on warm/hot days.  It's a benign system that doesn't hinder engine performance, so I would leave it intact.

[thefarmboy21]

So IF I don't want to run the EFE valve, I can just put a vacuum cap on it? Or does it actually need dismantled? Also IF I do want to use it, what port does it need hooked into?

The vapor canister is already taken off.....I'm now trying to get it all back together. I don't necessarily car about fuel odor, it's just an old farm truck. I've only put 3000ish miles on it in the last 2 1/2 years.

The gist of it all is that the old six cyl is probably getting swapped for a 350 in the near future. I just needed to be able to have it mobile until that point and the smog system and carb had finally all had it.

[bd]

If you remove the EFE valve you'll have to reconfigure the headpipe connection to the manifold.  The EFE butterfly defaults open, so just leave it.

[thefarmboy21]

Thanks! I had just found that on another forum and was going to post about it. I never knew how much stuff was on these things until I started trying to get rid of it all lol. I believe I've got everything hooked up and plugged off the way I need to, now just to fine tune it once I fire it up.

I do have another question though: on the monojet carb, all the ports have a letter around them somewhere....suck as D, F, etc. There's a 3/8 fitting above the accelerator pump/float bowel area....what is it and does it need plugged or plumbed somewhere? Originally it went to the canister.

[bd]

The 3/8" fuel bowl "vent" needs to be open to atmosphere - on a farm truck, preferably through a filter to prevent entry of dust.

[thefarmboy21]

So it's a vent....and the carb won't function with it plugged off? I'm just used to holley's and Edelbrocks, etc....just didn't see the harm in having it plugged since nothing else has one.

[bd]

The float bowl has to be vented for proper fuel delivery from the main nozzle.  Although the 1 BBL redundantly vents the bowl into the air horn, if you cap the external 3/8" vent tube, you may experience fuel delivery problems as the air filter becomes restricted (a common occurrence on farm trucks).

[thefarmboy21]

Well I appreciate the help. I guess maybe to simplify things I should just put the charcoal can back in and only hook up the tank vent and carb fuel vent....then just leave the other ports on the can open?

And is the heater selector valve vacuum operated on an 86 or electric? I don't recall pulling any lone from the cab anywhere and I don see any open ports....but I keep reading that it's vacuum operated?

[bd]

If you're going to reinstall the vapor canister to vent the carb bowl and fuel tank, you should also connect the canister purge vacuum lines to evacuate the accumulated fumes.

Factory 'heat' is cable operated.  Only the factory 'AC/heat' or HVAC is vacuum operated.

[thefarmboy21]

Does the carb fuel vent push vapors out or pull air in....or both? Would it be a problem to run a hose from on of the air cleaner ports behind the filter (filtered air) or would this create issues?

I just want this to run efficiently as possible while doing away with the most stuff in the engine bay as I can. The squalling, sputtering, backfiring and 7mpg weren't cutting it. This truck WAS my grandpas farm truck, now with only 82,000 miles it's mine to just drive occasionally. It sees dirt roads and blacktop both, but no big loads and rarely any highway. It's just a good, solid, low miles, family heirloom that I enjoy just driving. Just a farm boys parts picker-upper/Sunday driver if you will. This summer or fall the motor has to be pulled OR trans dropped to change a bad throw out bearing.....if I can get it to run better, the motor stays maybe....if not it's getting a 350 at that time. Either way I need to to run reliably until then lol.

[bd]

Does the carb fuel vent push vapors out or pull air in....or both? Would it be a problem to run a hose from on of the air cleaner ports behind the filter (filtered air) or would this create issues?

Fuel vapor exits the bowl, atmospheric pressure pressurizes the bowl.  The carb will perform best with the fuel bowl venting through a filter that is independent of, and located "outside" of, the intake air filter.  It really only becomes an issue when the intake air filter begins to restrict from dust accumulation.

[thefarmboy21]

Ok, so maybe a cheap inline fuel filter just kinda hanging out then? Hopefully tonight or tomorrow I can get everything hooked back up so I can see if it's gonna run ok or not....the carb needs a new jet and metering rod but no one had any that were big enough. The biggest that "quadrajetsparts.com" had were still several sizes too small. One of these days in gonna hotrod that little 6 and add a 4bbl Offy intake lol

[thefarmboy21]

Well I finally fired the old 6 cylinder up after 2 1/2 months of sitting.....carb is spewing gas and runs like a half dead slaughter hog
I guess all that carbon/oil/farm dirt, tar like mixture is what kept it in all these years. It's leaking either down the accelerator pump rod that oddly comes down through the bottom or the throttle plate rod that goes through and works that particular linkage. It's bittersweet as now it's definitely getting the 350 soon. It just sucks because now it's going to be down that much longer and I have to find time to build a motor and swap it in. Ahhh well....so goes the life of a gear head. Thanks for all the help anyway.