Stewart carb problems

[16Dodger7]

I have a 1916 Dodge Brothers touring car, with the Stewart model 25 carburetor. I seem to have an obscure fuel problem, and would appreciate any help that is forthcoming. 

The car will fire, but not (usually) run. Acts like it is consistently starving for fuel. I do have a mechanic's manual for this car, and have set the carb as per factory specs. Carburetor has been disassembled and thoroughly cleaned. There is fuel in the fuel bowel float chamber on the carb. I went so far as to mount a small auxiliary fuel tank on the firewall and plumb it directly to the carb, so as to bypass the whole vacuum tank system. No change on symptoms. 

 

This car was a daily driver till recently, which is why I'm so baffled at this problem. Any insight would be much appreciated. 

[Mark Gregush]

Do you have the enricher cable hooked up? (Sure Dodge called it something else, but thats what I call it)

[robert b]

AIR  VALVE STICKING, TO LEAN NEEDLE SETING ,DAMPER CHECK VALVES NOT FREE IN LOWER AIR VALVE BASE. THE MOST COMON IS AIR VALVE STICKING  BOB

[22touring]

The metering valve stem is supposed to be attached to the head of the metering valve.  Is it?  Originally they were swaged together, but the swaging eventually fails.  Then the head will lift but the stem won't follow, so no fuel can get in.  I had to solder the head and stem of mine together.  It is not obvious upon a visual inspection that they are supposed to be attached, so it is necessary to know a little bit about the carb's manner of operation in order to diagnose it. 

[MikeC5]

That's what I was thinking too.

[16Dodger7]

Thank you all for the feedback!

Yes, the mixture control cable to the bottom of the carburetor is hooked up and properly indexed. I will check the metering valve stem, as suggested by 22touring. That sounds like a definite possible culprit. My reprint Dodge Brothers shop manual has a good diagram of the carb, so I should be able to figure the thing out. Part of my problem is ignorance - the Stewart carb is very unlike anything I've dealt with before. My knowledge of tractors and small-block Chevys is of limited use here. 

Again, thanks for the pointers. I will post what I come up with. May be a few days. 

[22touring]

16Dodger7, don't feel too badly about not being able to diagnose the problem right away. When I had the same problem, I tried to fix it *repeatedly* and would then go on a test run.  My car would run for about a mile, but when I got to the first stop sign and let the engine idle, it would die and I had to be towed home.  OF COURSE I claimed the towing jobs under the towing insurance coverage of my auto insurance policy!  At least I DID claim it, until the carrier sent me a notice cancelling the towing coverage and stating in no uncertain terms that if I ever tried to buy towing insurance from them in the future it would be grounds for terminating my policy completely.  And what's more, I don't really blame them for feeling that way because *repeatedly* is an understatement!

Edited October 12, 2022 by 22touring
typo (see edit history)

[Mark Gregush]

I had the air valve stick and car stopped running at about the same point, 1 mile , was running and driving fine the trips before that. Thought it was points as they had been giving me issues. Cleaned points while people took photos and asked questions after pushing the car to side of road at a stop sign. Got the car running, badly, and was able to get back home. I had cleaned the carb shortly before all this but when I took it off after this trip, there was a lot of powdery dirt keeping the air valve from freely moving. Unless when I had cleaned it, didn't take the air valve apart no pin spanner, missed it or just didn't get it all out because it was not coming from the gas tank or through the preheater/exhaust manifold end. Cleaned it again and has been running fine. 

[16Dodger7]

So, I have an update. 

After further perusal, I determined that the metering valve and stem are attached to each other. I tried indexing the needle on the rack lower, to richen the mixture. Did then get it to run, weakly. As far as I can ascertain, all internal passages, check valves, and parts are free, clear, and functioning. 

As an added bit of puzzlement, I notice that the intake manifold passages (which are integral to the block on this engine) have fuel pooled in them. This does not of course fit with having a fuel starvation problem. 

This engine has had some serious work done recently,  so its internal condition is top-notch. Timing set per manual, which is done using valve action on this engine. 

So, am I somehow barking up the wrong tree by assuming I have a carburetion issue? The old girl will run, just very poorly, and not for long. I'm open to any further guidance. 

And don't be afraid of denting my ego by asking if I've performed basic checks and tests....mercy, I'm in no position to get cocky. 

Many thanks in advance!

[Mark Gregush]

Maybe the top-notch internals are too tight and need to settle in some? 

[MikeC5]

Are you sure the valves are adjusted properly?  If valve/tappet clearance is too tight, the valve won't fully close when engine s warmed up.  Have you done a compression check or leakdown test?  Still a good idea to verify the basics.

[16Dodger7]

The compression is good with the crank. I will run an actual compression and vacuum check so I have numbers to back up that statement. Valve lash is spec, and I'm picky about those things.  Engine is certainly tight, what with all the work done, but not obstinately so. 

I feel like I'm getting mixed reads on the symptoms: I have fuel pooling in the intake, but if I can get it to run at all, I do so by richening the mixture control. 

I'll keep trying, and thank you for the input.

[Minibago]

With the engine fully rebuilt correctly it should not be tight. 
The (white metal) bearing width and splash feed require a larger bearing clearance than the modern motor car. (And oil dispersal grooves X shaped to ensure the outer bearing surface gets lubricated)

Any tightness in the bearings on startup will create heat, expansion and risks running a bearing.

 

[Mark Gregush]

You could have a lot of drag from the rings against the honed cylinders. 

[Minibago]

You are quite right Mark, again initial tightness will create heat.

We have had experience here in Oz with the modern, three piece oil ring being too good, removing all the necessary lubrication from the cylinder walls far quicker than it can be replaced. Several long term owners recommend changing to a cast iron one piece oil ring to avoid this.

[Minibago]

The Stewart carby is pretty reliable and if there is residual fuel in the intake then I would focus on something other than the carby.

[nearchoclatetown]

Is this a magneto or Delco car? How did you time it?

[Mark Gregush]

Too much fuel, flooding, can bog an engine down. When you set the air valve, was it seated or maybe partly open? Once the car starts, engine vacuum keeps it open. Do a compression test. Just because the engine was rebuilt at some point would not rule out sticking or valve that is not closing all the way or the cold gap is too small. 

When setting the valve clearance, the engine needs to be up to operating temperature not cold, for the values given.

Are you going by the instructions given in the Mechanics' Instruction Manual or Book of Information?

As you cannot get the engine to run all that long, at this point you might want to open the gaps up some till you can get the engine to keep running. Once you get to the point the engine will run and can get up to temperature, then readdress the valve gap. 

[16Dodger7]

Many thanks for the input. 

In the interests of full clarity, this is my elderly father's car, and he is in the generation that doesn't do Internet, so I am trying to render what assistance I can in that regard.

However, I have been involved with the 16 enough to have a pretty clear idea of symptoms and actions.

It's Delco battery ignition, not magneto.

Carb has been set per factory specs in Mechanic's Manual.

Timing is set using procedure outlined in Manual. 

Engine was rebuilt by a local machine shop. After reading Mark and Minibago's posts, that makes me uneasy. Perhaps the shop did not clearly understand the specs and tolerances this elderly engine operates under? 

We've been pulling it with a tractor to start it...maybe that's a bad idea, if the internal tolerances on the engine are too tight.

I probably agree with Minibago that carburetion is not the culprit here.

I will run a compression check on the old girl, and see what values that gives.

A complicating factor is that the car is not at my place, and I have dairy cows, so I can't help wrench as often as would be ideal.

Again, thanks to all for the advice; we will persist until we get it.

[Minibago]

Please do not try to start this car again until inspection of the crankshaft and bearings and the pistons / rings / cylinder walls has been completed.

I have a 1919 Touring car and at the time had no vintage car experience, my machining work was done by a company who came highly recommended, no oil grooves were machined in the bearings and when queried they insisted none were needed. I re-assembled the engine and found it very tight, it would turn reluctantly on the handle but not with the electric starter. My questioning of other Dodge owners produced varied opinions on the need for oil grooves.

I researched from an engineering perspective and the accepted practice is for the width of the bearing surface to be taken into consideration along with the bearing material and the fact that the Dodge has a splash feed oil system. 
On dismantling I found the bearings had been grabbing on the leading and trailing edges despite copious amounts of assembly lube (I guess the line boring was a Friday afternoon job) the clearance on the centre of the bearing journal was okay so obviously not round.

 

If the oil grooves have not been included then the centre (about 3/4 of an inch) of the bearing will get oil but it will not spread sideways to the outer areas and the bearing white metal will heat up and pick up on the crank.

Good luck.

[16Dodger7]

Minibago, I appreciate your expertise. This is starting to explain the situation. Dad will not be overjoyed to hear that we should pull the engine back out and look at it. 

I am learning here, definitely: an International tractor pumping 50psi oil through insert bearings is a whole different animal from a 1916 DB splashing 6psi on babbits. 

[16Dodger7]

Nat, I appreciate your advice. I'll try rolling the engine with the crank, plugs out, but I think I'll need to convince dad we need to drop the pan and check bearings and crank journals. I'm glad to hear the pan comes off with the engine in chassis. 

I don't believe the 16 has run, or not properly, since the motor came back from the shop. We may soon find out why. 

I'll post more when I know more. I am grateful for all the input, thanks.

[16Dodger7]

So, had a few minutes to check the 16 a bit. As Nat correctly said, never assume anything. This was borne out with a compression check. 

The Mechanic's Manual gives 55psi at cranking speed as a basic spec. With me whipping the crank, we should be getting an accurate read. Thus, we had best start by pulling the head. We will know more when we get things apart, but it seems a reasonable assumption that there's been some careless machine shop work. (The shop in question is no longer in business). We will plan to drop the pan also, to ascertain conditions on the bottom end. I will post more as I know more. Many thanks for the ongoing help. 

[MikeC5]

I hope it's only dry rings and a sticky valve.  But I still think you should check those bearings too.

[RAH]

Guys, Sorry I do not recall what the fuel source to the carb was mentioned up front. Is it Vaccuum Tank, or Pressurized Fuel system? If it is vaccuum tank, I would check the carb outlet port between the #2 and #3 cylinder for excessive fuel. IF the vaccuum port inside that tank is NOT plugged properly the unit will fill the inner AND outer tanks and run raw fuel down the vac. line essentially bypassing the carb.  Unfortunately a substantial number of carb. problems are NOT carb. problems rather vaccuum tank OR electrical. Just asking.

[MikeC5]

I think he said it was no improvement when trying on gravity feed from a can.  But you do make a good point that fuel pooling on #2 and 3 is suspicious of a vacuum tank problem with vacuum port which can lead to fuel being sucked into the vacuum supply line from vacuum tank to inlet 'manifold' (not really a manifold; it's only 1).  That line  would deposit fuel between #2 and 3...  I'm guessing it wold be best to stick with the ausilliary fuel tank until you can get it running properly, then open up the vacuum tank and take a look.  I met a vendor at Hershey who specializes in rebuilding vacuum tanks who did make a convincing argument that the little valve seat that are pressed into the lid are difficult to replace if you don't have the right technique and tools.  Let me know and I'll PM you his contact info. 

We know from your compression test that you probably have a valve problem on #3, so I would start diagnosing that first.  Just removing the tappet cover and hand cranking with the plugs out it should be easy to spot a sticky valve.  If you know someone who can take a look in the chamber with a borescope, that would most likely reveal the problem too.  As for the timing, iirc, a early car does not have markings on the flywheel  and you have to watch the valve open/close to set it properly (the BOI has the procedure).  Did you do this or did the shop claim they did?  Probably worth double checking if the latter.

[16Dodger7]

So, report. 

After some consideration, decided to pull the head. Valves had not been lapped in upon reassembly, and one valve on #3 was bent just below the valve head, which obviously accounts for the flat compression on that cylinder. Fair amount of carbon on things, a result of us fiddling with the carb mixture settings. Definitely, this is an internal engine problem, not a carb problem. 

Pulled off the front cover, verified alignment of timing marks, and set timing per procedure in Mechanic's Manual. Lapped in the valves, replaced the bent one, set them a little loose. Lubed up the cylinder walls, which were bone dry, no doubt from the extra gas washing things down. Cross hatch honing marks are still visible in the cylinders from the machine shop work.  Engine turns nice and easy, with the crank or with the starter. 

Machine shop did all the top end work, dad did the bearings. Given the current situation, I don't think I can convince him to drop the pan. The bearings do have oil grooves. Dad has been doing most of the wrenching, so I don't have pictures to post of the inside of the engine. 

I'm open to wisdom and input as this project continues. 

 

 

[JFranklin]

If I found this I would surely want to drop the pan at least for assurance the work there was up to snuff.

[MikeC5]

If oiling the rings freed things up and it turns easily without plugs in and your Dad is sure the bearings have oil grooves, maybe you don't have to drop the pan.  On the other hand, dropping the pan isn't all that difficult on these (at least it wasn't on my '25) and a quick look at the rod caps would be a good piece of mind.  I'm glad it was only a bent valve on #3 !

[16Dodger7]

Well, we have victory! Dad finished torquing things together, and the fire caught with the starter. All four are firing in line, no knocks, clatters, or rattles. 

I had wanted to get some pictures of the inside of the engine, but once dad had a lead on the likely problem, he did not waste time in attacking. 

 

I  am actually a bit embarrassed about this whole situation, as dad and I have enough wrench experience between us that we should have been able to diagnose this a little quicker. But like he said, a guy spends a bunch of money at the machine shop, he shouldn't have to double check their work. At any rate, now we know. 

 

I will try to post some pictures of the bent valve that came out of the #3 cylinder, and of the car, so everybody can see what the old girl looks like.  

Many thanks for all the sound advice and pointers. Very much appreciated!

[16Dodger7]

I should mention, for sake of clarity: the bearings do have oil grooves. Dad put the bottom end together, and he was aware of how things were supposed to look down there.