The Stovebolt Site Forums The Shop Area Engine Shop 261 Not Responsive

We've got what we believe is a 261 in a truck. It seems to be running lean at low rpm. Pull the choke out half way and it's crazy responsive, push the choke back in and you can kill the engine with quick throttle if you would want to. Always has sounded rough at part-mid throttle and occasionally can hear a small pop or miss out the exhaust at idle for as long as I can remember. Carb was just rebuilt. Going to try setting the air mixture with a vacuum gauge tomorrow. Any other ideas? One thing that I have thought of is the vacuum canister on the distributor pulling too much advance to soon. Is that a possibility?

Thanks

Your main problem is in the carb. It may not have come off a 261 originally. First make shure the accelerator pump is working. Look down the throte & work the throttle. you should get a squirt of gas each time you move the throttle off the stop. I assume you have a roch. model B. Take the top off & check the float level. Make shure the power piston goes into the hole & kicks the ball off it,s seat. You may have to go to a larger main jet or if you have the right drill bits you can drill it out .oo2-.003 inch.The part throttle surge may be caused by to much timeing or vacuum advance.

Thanks for replying. The float level should be set from when I rebuilt the carb. I never thought of checking the pump shot, just figured it was fine because it was accelerating.

If I can remember right when I rebuilt the carb it was missing a ball or spring, pretty sure it was a ball. I put the one from the kit in there. I'll have to double check the manual that came with the kit to picture it.

I'm back with another issue.

Well, ever since we've had the truck, it misses and pops randomly out the exhaust at idle. We lately have had some missing problems beyond idle rpm. Put new plugs in, that helped for a day. Seems that the rough running is inconsistant. The plugs brought some of the responsiveness back, but when the throttle is quickly pushed down it will hesitate or drop in rpm then pick up. That's when it's running good. I tried setting the idle up and it seemed to help. There's times it runs good and times it runs bad; more bad lately. But just pulling the choke out some (which does increase the rpm) helps the responsiveness when it's running good. When it's missing terribly, nothing helps.

Yesterday hauling the last load it started missing going in 3rd with a full load. Glad I made it back to the yard. I had the throttle down, was playing with the choke cable a bit to see if I could get it to clean up. It seemed when I pulled the choke full out it started to clean up, then I pushed the choke back in once it did, then it backfired very loud out of the exhaust a couple times. What is that saying? It looks like a lean condition, yet the exhaust smells rich at idle.

Could the distributor have anything to do with it? Is the vacuum advance supposed to move the distributor a lot. It seems that it moves it an excessive amount before the engine rpm even catches up, when you move the throttle.

Got a new set of points and condensor for it as well. Haven't tried that yet. Looks like you have to crawl inside the engine compartment for that. It's on a Viking 60.

Any ideas? I'd like to get it running good today. We are done needing it for the season, but i'd like to get it tuned for next season.

Thanks

Sounds like a exhaust valve sticking open. Try putting some marvel mistery oil in the fuel tank to see if that helps. You can also pull the valve cover and check the valve lash adjustment.

Had a similar problem with a 261 several years ago. The vacuum line to the dist. had a small leak and the intake gasket was leaking on the rear port. Changed those and it ran fine.

Arnie

Trever,

As people above have stated, it sounds like a vacuum leak somewhere.

There is a slightly dangerous but very effective way to check for vacuum leaks, using a propane torch.

Use this technique at your own risk. It does work.

Regarding a stuck valve - you could check this by taking off the valve cover, run or turn the engine, and see if all the valves move. If you have a truck 261 engine, it came with solid/mechanical lifters and a struck valve would cause more obvious problems (I think).

Some 261 engines were able to use hydraulic lifters (and I think the Canadian Pontiac 261 had hydraulic lifters). I know very little about hydraulic lifters but my guess is that a stuck valve might not be as obvious in those engines.

Also, an old-style vacuum tester might help you find the problem.

Tim

It could also be an obstructed fuel line or plugged filter, or a weak ignition coil. Take the fuel line off the carb and put it in a coffee can. Have someone just bump the engine over a little at a time. When the pump kicks you should get a fairly decent sized shot of fuel in the can. Pull the center wire out of the dist cap and lean it near some metal. Have someone crank it over and look at the spark, it should be bright blue, not yellow.

Make sure the carb spacer is in the right position.
It has a notch on one side. that feeds a little hole in the carb. If mounted in the wrong position your idle circuilt won`t work right at all.

This applyes not to all carbs, but it is worth a check.

Also make sure the throttle plate is almost closed at idle (one turn at the throttle screw - do the rest with the mixture screw). If the plate is open to wide, it overrides the idle circulit.

A vacuum gauge tells it all

Frank

Thanks

I've sprayed the carb base and the intake where it mates to the block with parts cleaner and didn't find anything with that. That's supposed to find vacuum leaks i'm told.

Is that hole on the spacer for vacuum? Where's the best place to check for vacuum? On my 48 Chrysler there was a fitting in the middle of the vacuum line that I could disconnect and tee into. The Chevy has a straight line from the carb to the vacuum can.

The darn thing starts great when warm. Used to start great all of the time. Just turn the key and it's started before you know it. Lately its needed pumping of the accelerator and full choke to start, then it runs rough, if it starts. Sometimes it will fire up but die right away.

Another thing I wonder is if it's starving for fuel. That's been what I was thinking for awhile. There is no inline fuel filter on the fuel system from the pump to the carb. They must have not had one from the factory. I drove it yesterday thinking that I could drive it down to the end of the mile and back. I got less than a 1/4 mile and I threw her in reverse because it was missing so bad after I got it in third. Right away pulling out of the driveway I could definately feel it surging like it was starving for fuel. It would miss and pop out the exhaust, then it would clean up. But it eventually got so bad that I just backed up and was glad that I made it. So I wonder if it is starving for fuel, yet the exhaust smells rich and is black on accel out of the exhaust.

Read your spark plugs. Remove 2 plugs & see if the porceline is black. With todays gas especially when it is old can carbon up plugs in a short time. Clean the plugs if nessary & try it again. I think you will have to go back in the carb. & see why it,s running rich. A vacuum gauge can be hooked to the outlet for the wipers. Don,t use the one to the dist. It usually is on ported vacuum.

Did you set the timing at all? Did you set the point gap/dwell? If you do not have those spot-on then do not mess with the carb or anything else until you do.

The vacuum advance should move the distributor quite a bit. It has detents built into the mechanism and should not give you trouble.

While you have the dist. open, check to make sure the centrifugal advance is working. The weights are under the breaker point plate, and they need to move freely and the springs should be present.

It sounds to me like your point gap is messed up and you need to reset it and adjust the timing, then revisit the carb if that doesn't fix it. Troubleshooting should always start by fixing the ignition first.

I ran a vacuum gauge off the vacuum port of the carb this morning, after I got the truck started and running by itself. I get only 6" at idle, and up to around 15" with the choke out aways (but not out all the way where it starves for air). The needle is as steady as can be though.

Then I decided to remove the fuel line off the carb and either check for fuel or remove the carb check for the hole in the base. As I was loosening the fitting on the line up by the carb, all of a sudden it started spraying out from the fitting. It sprayed out for a few seconds then I tightened the fitting back up. I didn't expect that much pressure. Few minutes later I came back to it and removed it as well as the carb. The hole on the spacer lined up with the notch cut out on the gasket, which lined up with the hole in the base of the carb.

Then I thought I might as well take the carb apart while its off. I took it apart and blew all the passages out with air. I did note that it was missing a couple of check balls, and a mesh screen in the main well that the diagram shows it should have. I found a check ball in the rebuild kit box that I kept from when I did the rebuild. I put that in underneath the spring and t-shaped piece that pushes in the carb. I found another check ball from another kit to put in the other spot on the removable main well, but turns out it was too big. Now the spring and ball are stuck in the screw that goes in the hole of the main well underneath the piston and spring, and I don't think it's going to come out. I tried using a vise, and a vacuum pump, and it isn't coming out. I also reset the float adjustment and checked the float drop, both are spot on now at 1 9/32 and 1 3/4.

I figure I shouldn't put the carb back on and run it until I figure out some fuel filter setup for the truck. Did they ever have a fuel filter?

I will probably pull the plugs and check them out again. Should I do that and check the ignition before I get the carb back on and get it running? I checked the point gap a couple weeks ago or so when I put in new plugs and it seemed to be narrow IMO. What's it supposed to be? 0.016"? Never checked the timing as long as i've been around it. Running it, it sounds like it has a load on it all the time except for at idle, so maybe it is a bit retarded?

After running it today, and then trying to restart it, it doesn't start up as quick as it used to. Usually after ran it will fire up right away. Now it either takes pump shots with the accelerator, or else 3-4 seconds of cranking and the engine will slowly overcome the starter and start.

ya shouldnt just guess at what ball goes where?? or the sizes of balls either.. if choking it only brings up the vacuum gauge at idle then you have a vacuum leak, and thats what sounds like the biggest problem??? what kind of carb is it.. is it a roch two barrel maybe..?? if so those can have a small filter under the nut where the fuel line goes in. And if you got that much pressure pulling the fuel line with it shut off?? sounds like at least the needle and seat are holding, but are you sure its set right and letting enough fuel in the float bowl??? It also still sounds like it could be a flow problem like a filter plugged or intank screen plugged... did you trace the fuel line back to the tank,? as in an inline filter added someplace??? if it runs better with the choke on, it is either fuel flow or vacuum leak, i dont think its running to rich....still could be the carb too if you got the balls mixed up or missing.. ????

You need to retime it every time you do anthing with the points and distributor. When in doubt, check the timing before touching the carb.

Where else do I find a reference of the size of the balls? They aren't marked a certain size. When I first went into the carb it didn't have any. And back years ago it ran fine that way. The carb is a Rochester B-series. Cranked the engine over to check fuel and it's getting plenty off fuel, and the pump is putting out 4 lbs. I checked the spark from the coil too and it is orange, not blue.

I haven't messed with the points ever, so haven't had a reason to mess with the timing.

It does run better with the choke on. I don't know if it is because of the rpm increase, or because it is normally running lean. Due to the fact that it hesitates then picks up when the accel is moved made me think it was an off-idle lean condition. But that wouldn't explain why it missed at high rpms and randomly popped out of the exhaust at idle. Also, how can it be lean and foul the plugs. All plugs were dark and dry (carboned) besides 3 and 4 which had tan ground straps and white porcelain.

What can we get off of the vacuum test that I did? The reason the vacuum increases is because the idle is higher. That's normal, I thought.

When you said vacuum 6" then with choke 15, you didnt say you increased the idle speed. It does sound more like ignition now. All i remember about the balls, is one of them is like a check valve, but i wouldnt think it would run right without them period..?? dunno..would have to look again... now you say youve never put points in,,??? or you never put points in this time..??? do you know what the points look like or are they breaking or did ya check the gap..?? First off it kinda sounds like thats the place to go now...is id put points condenser and rotor in it...and then check from there.... and its hard to tell the way you described how much better it run with the choke on..??? choke on wont fix points.. LOL.. there again... hard to fix a car online by listenin to whirs hammers and bangin described by someone else... hehehe... so ill shut up for now...

Check list:
Valves - is valve timing and clearance correct?
Ignition Points - Set gap
Spark Plugs - Clean and gap/check dwell angle
Distributor cap and rotor - Clean and check for cracks
Distributor shaft - Check for excessive play
Plug wires - Check conditon and for correct firing order
Ignition timing - Set with vacuum advance disconnected
Vacuum and centrifugal advance - check function
Compression - Check
Carburettor - Fuel filter, float level, accel. pump volume, mixture, idle speed
Manifolds - Vacuum and exhaust leaks

Yeah the cam on the choke system increases the idle when the choke is on, to keep the engine from choking. I've never put points in. They may have been replaced in the past, but not by me. There is spark at the points, and orange spark from the coil. I pulled the valve cover and the valves are all moving. Never went through and checked lash, as i'm not sure what kind of lifters are in the engine. It is a truck engine, and there was lash in the rockers (not preload), so i'm assuming they're solid. Yeah, like I said, the engine ran before without any of the check balls in so..... ???

The whole having the choke on deal is hard for me to understand as well. For one thing, it gets rid of the hesitation that there is when stepping on the pedal. I don't know if that is because it is running at a higher rpm, or if its because the carb is now off the idle circuit and on the main circuit. As far as I can tell, it doesn't help the missing at all. The missing isn't something that is always there. Somedays it will run fine and not miss, somedays it will start to miss after it is ran for awhile, somedays it will miss right away after startup. Seems to miss more often than not lately. Plugs seemed to fix the missing, but only temporarily, then the plugs get dark again. 4 of the 6 were dark today.

And the popping at idle is just something that it randomly does. When running it idles as smooth as can be, but still will softly pop out the exhaust randomly.

Plug wires are new and in correct order. Plugs are gapped at .035". Vacuum advance is working. Carb is getting plenty of fuel. Floats are set to spec. Carb has good pump shot. Idle is good. Sprayed carb cleaner around intake air sealing areas and couldn't detect any increase in rpms.

Try replacing the condenser

Why are you so resistant to checking the timing? Points and condensors on non electronic ignition systems should be replaced every 10K miles for good performance, every 6K for optimum performance. Point gap and timing change with wear. Orange spark from HT circuit is inadequate. Too retarded timing requires a richer mixture and causes exhaust popping.

Because I have no idea what it's supposed to be. For all I know when the motor was gone through several years ago it could have been timed by ear.

What causes orange spark? Bad coil? Does orange spark mean it doesn't put out a hot enough spark?

Trever Maas,

I think the general sentiment of the posts here is this; you have to start at the top of your check list and work down. Find some dope on the timing and set it properly, now you know that's correct. Verifty the point gap and quality of cap, rotor, wires etc, now thats off the list. Keep working away, making sure each system is perfect, through this process you will eleminate most variables and end up with one item which is the problem. Find a manual or spec sheet for your rig..adjust it to the recommended settings.


Stuart.

Too bad there isn't a just of what causes what, as I just came back from town with a coil, rotor, and another carb kit and ended up with a $70 bill. Usually when something is wrong you can point fingers at what is the culprit. Just like the troubleshooting section in the Haynes manual.

I want to make sure of how to check things. How do you check a coil? What does testing wires with an ohmmeter tell you? What determines if a cap is good?

Now that I got this carb kit, how do you know which check ball goes where? They maybe show a picture of them, but there's no reference to size?

Trever Maas,

I know exactly what you are saying. It is frustrating not being able to go to one component and say, this is the culprit! What we are talking about is the "E" word. EXPERIENCE, and you are getting it right now. If you do everything right, next time it will be that much easier.

I think the carburetor kit has a set of foolproof instructions included..it shows ball location AND size. Take your time and follow each step carefully. I'm sure more advice is right around the cyber-corner.


Stuart.

Still no points and condenser?

Trever, for what it is worth, all of your troubles may not be fixed by replacing one part. It is very possible that the timing could be causing the back firing and the missing, while the carb is causing the truck to want to die on depression of the throttle. I firmly feel that you need to replace your points and condenser. A chain is only as good as its weakest link. You should also check the valve lash. A tight valve can cause the backfires that you are reporting.

Phil

I know what you are going throu Trever.
Something like this can drive a guy nuts.

O.K. lets try to pinpoint the problem down.

Symtoms:
1. It is responsive with choke
2. when the throttle is quickly pushed down it will hesitate
3. New Plugs help only for a short time only
4. Vacuum reading is 6 to 15 (with choke)
5. Balls in the carb missing or maybe wrong size

The missing/hesitation you report sounds like ignition (points maybe but more like condenser to me)

But that`s not your main Problem

Let`s start with Vacuum - mormal is 17-20.
When you rev her up the reading goes down.
If it goes up you got the wrong port. You need manifold vaccum.

Low bud steady reading pints to:

A - Late timing
B - low compression
C - sticking throttle valve
D - carb or manifold vacuum leak

A - You say timing is correct. (Just to make sure try to twist the dizzy a bit in both directions and see if that helps. Maybe the clamp went loose.)Popping from the exhaust means unburned gas (no spark)

B - If you have full power with choke we can also forget this
C - I don`t think so, cause that`s eays to check and you had the carb out already.
D - our best bet so far.

A Vaccum leak would explain why you get better response with the choke. It would also explain the dark plugs, cause you are running way to rich with the choke.

Second best bet would be a carb problem that causes lean mixture and explain all the symptoms.

here is a link that tells you about different vaccum gauge readings: Vaccum Tuning


The easyest way would be to borrow an other carb and bolt it on. If not try the new rebuild kit and get that dammed ball out ther first. An for goodnes sake, do the most eaysest thing first: replace the condenser.

Good Luck, Frank

Went at her this afternoon.

First thing that I did was cleaned the plugs and got them back in. Then I had someone run the engine while I probed around the intake-related areas of the engine with a propane torch. Didn't find any leaks with that, also didn't find any with the carb cleaner that I used the other day. Checked the points and they weren't sparking in the right spot (they were sparking on the outside). Grabbed the new set of points and condensor that were picked up days ago. Turns out that the points weren't the same style. The new set doesn't have a hole for the lock screw (has a different style base). Found a new set that looked identical in the cabinet. Didn't work right. Put the new condensor in with the old bracket and screw, and put the old set of points back in it. Had someone else put the points and condensor in and set them while I was changing plugs and checking a cylinder on my MM. They set them so they sparked good. I'm not sure where they were set at, FWIW. Put the new rotor on as well.

Started it up after a bit of pumping and restarting. There was no missing at all, but I still had the slight popping randomly out of the exhaust, and the acclerator hesitation was still there. You can hear the carb sucking air (shhhhh noise) until it catches up. Doesn't do it with the choke on at all.

So then I decided to advance the timing, upon another persons opinion that it may be late. I loosened the screw and he turned the distributor, of which I would say it was a generous advance (but I don't know where I was to begin with). I would say that this made the most difference. The slight popping out of the exhaust diminished (but not fully) and the hesitation improved some (but maybe that is because the timing raised the idle up some).

I should note that there is no hesitation after idle. I have to think that it isn't the acual choking of the engine that makes it so it doesn't hesitate, but that the choke cam moves the throttle and increases the rpm. That's just my thinking. That all could be related to those balls in the carb either not in the right spot or the wrong size. Yet that could spell vacuum leak as well, but if I checked for leaks with propane and carb cleaner there shouldn't be any.

Then after I set the timing and locked it down, I was told to reset the air screw. I tried to turn it in just to see what happens, of course it made it idle worse. So I richened it up a bit.

After trying to drive the truck out of the shop around another vehicle, I managed to just touch the air cleaner on the floor with one of the rear duals and it crinkled it up (which i'm not happy about). I was told that it was clear to drive out, I was hesitant but I did, and as I was driving out I looked in the mirror and saw the air cleaner on the floor, and right as I saw it I saw it push the one way (which didn't give me a good feeling). Anyways, took it out. No missing or popping in the normal rpm range. I could definately hear and feel the points breaking up, but I was told that I didn't need to run the engine at that high of rpms, so the points in there should be fine. ??? I tryed to really load the engine up by shifting into 5th, holding the throttle down, and slowly applying the brake. Couldn't get the engine to miss. One time it bogged, but didn't miss at all.

So the missing seems to be taken care of for now. Popping is a lot better than it was, but is ever so slightly noticeable some times. Not quite as loud as it was before though. Still have that hesitation. If the throttle is eased into very slowly it won't hesitate. My Chrysler did the same thing when I wasn't running it with a pedal, just the rod out of the floor. After I put a pedal on it I don't think the throttle had to act as quick, so it didn't hesitate.

I never installed the coil. Was told today that the coil that was in the truck didn't work when the truck was bought by the prior owner (relative), so the guy went out back in the grove and pulled a coil off of another truck. And it's worked for 20 years. Coil that was in it is still in the glove box, no good of course.

The darned truck kicks over like a dream. Always has. Lately it's needed pumping of the throttle to get a good pump shot in it before it will start. Used to start up without the shot of gas. But as far as the starting goes, I would think that it has a good ignition system. Today after the work that I did, it starts different. It will kick over and act like it is running, then sound like it is stalling, then it starts running. All in the matter of a second or two. That's with no throttle. I think with the choke on and throttle applied it will fire right up and stay running without having that split second of hesitation. It starts up and stays running, just sounds like it's going to stall as it's starting.

What does it sound like I should do next? Get the check balls in the carb sorted out?

BTW, anyone have a reference to a number for a carb gasket? Does this application use one or two? The way it's set up now, it goes from the manifold to the square throttle bracket that sits on top of the manifold, to the carb spacer, to the gasket, and to the carb. That's the way everything sits? Does that sound right, or should there be a gasket in between the manifold and throttle bracket?

Thanks

Trever Maas,

What is the "square throttle bracket" thing?


Stuart.

It's the bracket for the throttle. Connects to the throttle cable on one end and the carb on the other. All one piece. It sits flat on the base of the intake, has holes for the carb studs and a big hole in the middle. Basically a throttle bracket that is held down by the carb. I shouldn't say it's square, but flat and follows the shape of the carb and spacer.