292 Questions

[May70]

Originally Posted by Steeveedee

I wouldn't replace the vacuum advance canister until I had verified that it was leaking. That's dirt simple. If you have a vacuum pump/gauge you can pump that and see if you can pull a vacuum that lasts. Or, you can blow into the vacuum line, if you don't have the pump/gauge. If there is a constant flow, the diaphragm is ruptured.

There is constant flow, no resistance when i blow in it.

[Mike_The_Grad]

With those black nitrophil floats you dont submerge them in water to find a leak. That only works on the brass soldered type floats. The way to check the black foam type of floats is to remove it from the carb and let it sit on a paper towel until it dries out. Really depends on the fuel evaporating. Then you can either still see where fuel is wicking out of any cracks or dunk it quickly into some fuel and pay attention to it evaporating. It should look like its evaporating somewhat evenly and not like there is a crack with fuel evaporating more slowly than the surrounding area. Definitely check where the metal arms enter the foam. It may look just fine when its dry but it will show any voids in the foam by way of evaporation. Dont use anything other than fuel to check for leaks. Brake cleaner, carb cleaner, starter fluid, water, acetone, etc. Will all either degrade the foam or soak in and take forever to evaporate if at all. There is a common suggestion regarding carburetor floats. And it goes," if the carb originally came with brass floats, stick to brass floats, or if foam, stick with foam. Dont change from one to the other. Also, try and source american made BRASS floats. As the import brass floats seem to have issues with the soldering process." I went through 3 different brass fuel sender floats before I got fed up with the vendor sending me more import floats that I switched to a plastic float that is near identical to the brass one. So far it works.

Your vacuum canister is definitely a vacuum leak and is why you see no change in timing when you tried sucking/blowing through it.

The purpose of using vacuum gauge while adjusting your idle/air screw is to attain the highest possible vacuum at the lowest acceptable idle. Your results reflect this. A rise in idle rpms will increase vacuum up to a certain extent. I like your reading of 1.5 turns out with 680 RPMs and 21.5" Hg. That is damn near perfect as you're gonna get. Tells me you have no issues with piston rings, head gasket, intake gasket, valve guides, or base timing. All good things.
BUT.
You have a vacuum leak. Just not at idle. Because the vacuum canister is hooked up to a ported vacuum source. Meaning it is a vacuum source above the throttle blades. Which is why you can idle it, but as soon as you give it gas, you open up a vacuum leak along with a malfunctioning vacuum assisted advance of your ignition timing. Compounding issues which may or may not be your only issues. Hopefully it is because your vacuum gauge readings seem good. The other thing about vacuum gauge readings is the steadiness of the needle during the reading of the state of the needle. Ideally it should be like the arm of a clock and not wander at all. Some slight movement is acceptable(within 1"-2"Hg.) But any erratic or continuous behavior is not.

My suggestion is to replace the vac canister and check everything again. I mean EVERYTHING. Timing, dwell, idle mixture screw, fast idle screw and vacuum gauge readings. My guess is that something is gonna change from your current setup. Those numbers I quoted up there are what you want to shoot for.
Remember, ADJUST timing with the vac can disconnected and RPMs below 750. But CHECK your timing with it both connected and disconnected.

Adjust your carb and rpms with it CONNECTED.

Good luck, I think your close to fixing your problem with the can. Let us know how it goes.

[Steeveedee]

Originally Posted by May70

There is constant flow, no resistance when i blow in it.

Yup, it's toast!

[May70]

Picked up the new vac can this morning. Checked it and the diaphragm is good on new one (better safe than sorry haha). Installed it and rechecked it all.

Dwell still 31
Advance needed to be reset to 12 degrees
Before messing with carb it was idling at 710 rpm

As the manual calls I did the same thing:

L6 Engines • 20 and 30 Series
Manual Transmission
Disconnect and plug distributor vacuum line.
Turn mixture screws in until lightly contacting
seats, then back screws out four times.
Adjust Carburetor idle speed screw to obtain 600
rpm with manual transmission in neutral.
Adjust mixture screw in to obtain 550 rpm with
manual transmission in neutral.
Reconnect distributor vacuum line.

Mix Screw Adjustment (Rotations out from seated), RPM, VAC (in Hg), Notes

4, 600, 20.5
3.5, 600, 20.5
3, 600, 20.5
2.5, 630, 21
2, 670, 21.25
1.75, 695, 21.5
1.5, 720, 21.8
1.25, 720, 22 **Returned to this
1, 670, 21.5
0.75, ---, --- (Vac and rpm dropped off, very rough idle)

Backed it up to 1.25 because that was my highest vac and stable rpm (although maybe a little high).

Took the truck around the loop in my backyard and the same thing is going on. Get up to maybe 2 or 3 mph just barely past a roll and it boggs out. As soon as you let off gas it returns to stable rpm.

I got the carb cleaner out and sprayed the carb. (see pic) does that hole above the distributor vac line suck fresh air or something? It seems odd its just open. When i spray carb cleaner at it or on the back near it the rpms drop 25 or 30....

[Motorfist]

I just popped out to the garage to see what I have going on where that hole is on your carb. My Monojet is a different casting and doesn’t even have the hole.

I was having similar issues but less extreme than you before I put the HEI in. It would idle great but when I would let the clutch out I REALLY had to be creative with the throttle to get the truck rolling. Hei made it all go away. I know you’ve put new points and Condenser in so you’re invested in figuring this out, but man. I feel for ya!

[Steeveedee]

Originally Posted by May70

Picked up the new vac can this morning. Checked it and the diaphragm is good on new one (better safe than sorry haha). Installed it and rechecked it all.

Dwell still 31
Advance needed to be reset to 12 degrees
Before messing with carb it was idling at 710 rpm

As the manual calls I did the same thing:

L6 Engines • 20 and 30 Series
Manual Transmission
Disconnect and plug distributor vacuum line.
Turn mixture screws in until lightly contacting
seats, then back screws out four times.
Adjust Carburetor idle speed screw to obtain 600
rpm with manual transmission in neutral.
Adjust mixture screw in to obtain 550 rpm with
manual transmission in neutral.
Reconnect distributor vacuum line.

Mix Screw Adjustment (Rotations out from seated), RPM, VAC (in Hg), Notes

4, 600, 20.5
3.5, 600, 20.5
3, 600, 20.5
2.5, 630, 21
2, 670, 21.25
1.75, 695, 21.5
1.5, 720, 21.8
1.25, 720, 22 **Returned to this
1, 670, 21.5
0.75, ---, --- (Vac and rpm dropped off, very rough idle)

Backed it up to 1.25 because that was my highest vac and stable rpm (although maybe a little high).

Took the truck around the loop in my backyard and the same thing is going on. Get up to maybe 2 or 3 mph just barely past a roll and it boggs out. As soon as you let off gas it returns to stable rpm.

I got the carb cleaner out and sprayed the carb. (see pic) does that hole above the distributor vac line suck fresh air or something? It seems odd its just open. When i spray carb cleaner at it or on the back near it the rpms drop 25 or 30....

That is probably a port for another vacuum line. Plug it with something easy to remove and see if it helps how the truck runs. I honestly can tell you that that small a vacuum leak can give you some bit of trouble. it's going to be incremental to get all the bugs worked out though. Stick with it, we'll get you through it! FWIW, if that is a vacuum leak, you are going to have to go back through the carburetor adjustments.

[straight6chevyguy]

Originally Posted by May70

I got the carb cleaner out and sprayed the carb. (see pic) does that hole above the distributor vac line suck fresh air or something? It seems odd its just open. When i spray carb cleaner at it or on the back near it the rpms drop 25 or 30....

Well you may have just found all or at least some of your problem!

That hole is DEFINITELY A VACUUM LEAK! (Unless someone can prove other wise)

I have two of this style monojet carbs and they both have two vacuum ports in the location in your picture.

I will run outside and snap a pic of the carb on my 65 for verification.

[straight6chevyguy]

Here's the pic's.
I hope I have been of some help.

[Mike_The_Grad]

That port appears to be above the throttle blades, but I could be wrong. If so, then it would also explain why at idle you have good vacuum and response from your carb adjustments but as soon as the throttle is cracked you have issues. When you adjust your carburetor do you flick the throttle at all with either your hand or foot? I do. Why? I dunno. Just something I thought would help "reset" the idle position to make sure it wasnt wedged or something. Anyways, I ask because I'm wondering if you have the same reaction while you're trying to drive the truck as if you were to manually work the throttle with your hand while under the hood. or if the engine only acts up while in gear and in motion.

[May70]

Originally Posted by straight6chevyguy

Here's the pic's.
I hope I have been of some help.

HMMMMMMMMMMMMMMMMMMMMMMMMMM. Before I started this it wasn't plugged. Just found an old pic of the carb.

The metal line that comes out of the vac port below it, are those aluminum? Not sure if my hardware store would have something like that

[May70]

Upon taking the carb off and getting out a magnifier, I saw that hole has a factory plug in it and it looks sealed in there good. Covered the hole up with gorrilla tape. No difference and still drops significantly when you spray carb cleaner on the back side. I think it might just be the gasket between the throttle body and carb. I spray it right on that gasket and it drops rpm. Not sure what else it could go through in that spot. The flanges are spotless and these are new gaskets. The flanges still have the tiny ridges around the hole ports etc so I know this hasnt been filed down unevenly etc.... Took the carb right off after truck got up to temp going around yard. This carb definitely gets HOT.

How tight do the screws need to be on this carb? I dont want to strip one out, I also want to be able to take it apart.

I have the carb apart now. Checking over things. Sprayed carb cleaner in each orifice on the carb. Im also not seeing anything wrong.

Do I need both of those gaskets (see pic) between the throttle body and the manifold? Or just the thick one? When i pulled it off the previous person put both. Thats what I put back but im not sure if that is correct and the instructions dont tell me.

A few days ago I took all the plugs out and cleaned them to shiny new with a soft brush and heat. I ran it a few times, drove around the yard between adjustments and you can see what the first 3 look like. The rest look like the 3rd spark plug. I just wanted to see how quick they are blackening. This also might be due more towards the valve seals on the first two because they were wet.

I want to confirm this is a too much fuel problem. Can I know that for sure?

I found a source for the carb vacuum tubing if anyone needs to get some later on reading this thread. Its aluminum. Will post back tonight with info and pics.

[May70]

Also found this (see pics): I thought I saw a video from mikes carburetor parts where he said this was in trucks that have AC? but the carb diagram doesnt mention cases which some carbs wouldnt have that 'idle compensation assy' and my kit did come with #17 gasket. Mine also looks to be blocked off?

//

I put the old float back in it and re adjusted the float level, just to see if the brand new 30$ float is garbage. I also took the jet out and made sure it was perfect, same with the needle. Adjusted the metering rod to spec (5/64 from bowl top). I made sure that the accelerator pump is working, I also made sure the check ball is seating and it is (holds a pressure against accelerator pump when i hold it down and try and plunge the pump). Other than that i blew out every orifice with carb cleaner again.

I put the screws back in snug then tapped around the flange on each gasket, then tightened them up real good (as mikes carb parts mentions to do in his monojet videos).

I have it back together now. Waiting to hear back on the manifold to throttle body gasket question. If this doesn't solve it im gunna have to take it to someone.

[Steeveedee]

OK, it's always run like crap since you bought it? I hate to ask you to take the carb back off, but let's have a look at the throttle body, the carb and the base gasket(s). It's clear now that that one port doesn't leak, so let's keep drilling for the answer.

[May70]

No it ran fine when I bought it in march and I could hop in and drive it when ever no worries. I had to feather the throttle when shifting or starting off to avoid a "neck breaker" (as someone who rode with me called it) but that was pretty much it. I figured it needed a carb cleaning at the time. Eventually it got harder to control the feathering good enough to make it enjoyable for anyone else to ride with me. A lot of rough starts(from stop).

Then I decided to change the oil because it looked like it had not been changed in a while and it was leaking from the valve cover/side covers a lot. So i knew I was either going to have to add oil or change it all. I changed the three gaskets then decided to change the oil a few weeks later. Shortly after I changed the oil it started the smoking, within a matter of a few short drives (~30 min ea). I would come to a stop and see/smell it come up by the cab. Eventually the smoke got worse to the point it is now.

The last time I actually drove it a few miles I was running 55 on the way home. All of a sudden it just lost power at high speed, but if I dropped it down to 35 or 40 maybe it was fine and I went straight home. That is when I started all of this and just decided I needed to go through everything.

I have the carb off now, Ill go out and snap some pics

[May70]

As i said earlier I changed to the old float and cleaned everything out again. Wanted to see how it did after all that. No difference. I went ahead and went through the adjustments just to see.

Mix Screw Adjustment (Rotations out from seated), RPM, VAC (in Hg), Notes

4, 600, 20
3.5, 600, 20
3, 600, 20
2.5, 600, 20
2, 630, 20
1.5, 680, 21
~1, 750( corrected to 650 via fast idle screw), 22 **Returned here (best vac)
.5-.75, ---, --- (Vac and rpm dropped off, very rough idle)

Still boggs out trying to get it going. When I first started it up I sprayed a lot of carb cleaner and no change in idle. After it was hot, I did get a slight reaction to the throttle body gasket on the back side. Could heat/warpage be causing a vacuum leak? The throttle body flange isnt perfect but I would be surprised if thats the culprit of the bogg situation. I may take it off and get a real flat surface to wet sand it on. Just speculation at this point.

[May70]

Had a friend come by to look at it. He thinks this is a lack of fuel problem. I sized up the jet/needle with the one that came in the kit (was slightly bigger than the one that was in it previously). No difference.

My in line fuel filter isnt emptying but its definitely not full at idle or even with a lot of throttle. Maybe half of the filter is full and when I put the throttle down I really dont see gas movement like I think I should. It has a slight pressure on it at idle because when i take the fuel line off after to remove the carb, some does squirt out. Is it possible that the mechanical fuel pump diaphragm has a crack in it or something and its not able to push enough gas to carb to keep up with rpm, resulting in the motor dying when I try and throttle it/start to go?

[Steeveedee]

Don't let the appearance of vapor in the filter fuel you. The engine can still be getting plenty of fuel, even when it looks like that. If it is under pressure, fuel is guaranteed to be getting to the carburetor. Any vapor that makes it to the carburetor will burp off immediately. I had a '66 Le Mans that turned high 13s in the quarter and the see-through filter always looked half-full. It may well be fuel delivery, but the appearance of that filter doesn't prove it.

Also, if when you remove the fuel line from the carburetor there is pressure, then the fuel pump diaphragm and poppet valve are not leaking. The more we see, the more culprits are eliminated.

I'll go back through this thread tomorrow and try to see if we're all missing something. Nothing I like better than making something work, though I'd rather have it in front of me instead of on the computer.

[Mike_The_Grad]

Well looking at your recent posts may have revealed something to my eye at least. It appears you have taper seat spark plugs. From what I understand these inline motors take the gasketed type spark plugs. I could totally be wrong but my parts guy informed me that the 250 cylinder head I had him go through for me takes the gasketed type. Does that mean all of them do? No, but it is something that could be contributing to your issues.
My buddy ran his 71 c10 from where he bought it to his place about 100 miles away. Well almost. The hei power wire fell off because it was wirenutted together. Anyways, he had taper seat plugs in his 041 head SBC, which takes the gasketed type of plugs. It ran sure, but not correctly.
Also, dont worry about the fuel filter being completely full or not. They usually aren't. But there is one thing you need to watch out for with the clear type of fuel filters. And that's to make sure the filter element inside doesnt come unglued from the base. Almost every clear one I've had has had this happen. The element ends up floating around inside and not doing its job. So I switched to the metal inline type. Yes, you cant see how much crap is inside. But that's why I made sure my fuel system was 100% clean to begin with. Tank, pickup tube, metal fuel lines from tank sender all the way to fuel pump, and to the carb, plus the carb. Filter between pump and carb. Use as minimal amount of rubber fuel line as possible. It dont hold up to long to today's ethanol fuel. Maintain same size line from tank to carb. In case this is all remedial stuff, I apologize. I figure information is information regardless of who is reading it.
Keep at it. Look at the positives. It starts, it runs, just not well. That's more than some people got going for them .

[May70]

For $18 I went out and got a carquest 'premium' mechanical fuel pump. Might as well narrow it down. Started the uninstall before it started thunder storming here. Noted that I only have about a foot, it appears, of rubber hose to replace. I think its metal fuel line all the way back to the tank and it looks to be in good shape under the oily gunk its been covered in for a while. The fuel pump outlet goes into a metal line which stops short about 5 inches from the carb. Then I have a few inches of rubber line with the inline filter.

I had prepared a plug because I was expecting a seep/drain of fuel when I took the hose off between the metal line to the tank and the hose to the pump. I got about 3 drops of gas and then nothing. There is at least a few gallons of gas in the tank. Is this normal? Can someone school me if there is a metal mesh filter or something in the tank outlet? Can I remove the gas cap and blow it out with an air hose or is that a bad idea? Just to make sure no debris is clogging it? Anything else I should do at this point or just throw the new pump on? Thanks

[Fbks_Cruiser]

You have definitely found a problem. Gas should be siphoning out of that fuel line aplenty. I would disconnect the line at the sending unit on the tank and while disconnected at the fuel pump blow some air to verify it is clear.

But, I suspect that the sock on the pickup is plugged with junk and the tank may also have sediment/rust in it. If you really only have a few gallons of gas in the tank, now is a good time to pull the sending unit and inspect the pickup screen and inside the tank.

[straight6chevyguy]

Originally Posted by May70

Upon taking the carb off and getting out a magnifier, I saw that hole has a factory plug in it and it looks sealed in there good.

Ok, It did cross my mind that maybe it was sealed off.

[straight6chevyguy]

Originally Posted by May70

Do I need both of those gaskets (see pic) between the throttle body and the manifold? Or just the thick one? When i pulled it off the previous person put both. Thats what I put back but im not sure if that is correct and the instructions dont tell me.

I believe You use just the thick one, but I'm no expert.

[straight6chevyguy]

I agree with Mike_The_Grad about the spark plugs.
My 292 takes the gasket type plugs.

[May70]

Originally Posted by straight6chevyguy

I agree with Mike_The_Grad about the spark plugs.
My 292 takes the gasket type plugs.

Anyone got a number? Parts store has the 292 coming up as having the tapered plugs. When I go to summit I see both listed for a 292. I will do some research on the side if no one has that info off the top.

[Motorfist]

I’ve got AC Delco R44XL in mine. I think the Autolite number is 404. That should be enough info to cross reference to whatever brand you prefer.