Drivability issues, can’t tell if rich or lean

[Jake Fleming]

Hi all,
I’m having some trouble with my Newport and I’m hoping to get some guidance. I was having an issue where the car would bog down/stutter/miss so bad pulling away from a stop you’d have to be careful not to stall. So I rebuilt the carburetor, it’s a Stromberg WWC, and today is the first day I’ve driven it a lot. It all seemed to be fixed at first but after about an hour of running around, now that the car is good and warm, it’s back. I think it’s running rich because even when I’m going down the road, if I give the pedal a good shot to fire the accelerator pump it’ll stutter for a second. But I’m not so sure because as I said the problem was there before the rebuild too. The car ran great for as long as I’ve had it before this issue.

 

[67Monaco]

tune it with a vacuum gauge. Its the only way I resolved my bog. It was all in the timing. I chased the carb for oh about 2.5 years. Without the vacuum gauge you're just guessing.

Classic Inlines - Tuning with a Vacuum Gage

 

[Jake Fleming]

tune it with a vacuum gauge. Its the only way I resolved my bog. It was all in the timing. I chased the carb for oh about 2.5 years. Without the vacuum gauge you're just guessing.

Classic Inlines - Tuning with a Vacuum Gage

I tuned it with a vacuum gauge when I put the carb on, I can double check everything that’s a good start. It may be worth noting that the vacuum gauge fluttered quite a bit which I imagine indicates news I won’t like.

 

[Jake Fleming]

Also if it helps, I’ve noticed that at mid-throttle it stutters and bogs even if I’m already at speed, goes away if I back off.

 

[67Monaco]

Also if it helps, I’ve noticed that at mid-throttle it stutters and bogs even if I’m already at speed, goes away if I back off.

That tells me you're probably lean.

 

[Davea Lux]

Since it worked for an hour or so, I think you might have a piece of crud in the carb that is plugging up one of the main jets. Also check your heat riser to be sure it is not stuck shut, that will boil the carb and create the condition you describe once the car warms up.

Dave

 

[Jake Fleming]

Since it worked for an hour or so, I think you might have a piece of crud in the carb that is plugging up one of the main jets. Also check your heat riser to be sure it is not stuck shut, that will boil the carb and create the condition you describe once the car warms up.

Dave

Ok. Going off that, and the lean advice 67 Monaco suggested I grabbed a new fuel filter while I’m out. It’s definitely getting worse as the day goes on. I’ll look inside the float bowl. Where would the heat riser be on a 383?

 

[Jake Fleming]

Ok. Going off that, and the lean advice 67 Monaco suggested I grabbed a new fuel filter while I’m out. It’s definitely getting worse as the day goes on. I’ll look inside the float bowl. Where would the heat riser be on a 383?

Correction I found the heat riser, it’s moving free but I would call it non operational. I can flip it to either position and it stays. Which way is open?

 

[Jake Fleming]

Some more troubleshooting and I’m back to thinking it’s too rich. I’m able to pump the accelerator level by hand without disturbing the throttle and giving it a shot of gas like that makes it almost stall

 

[Davea Lux]

Correction I found the heat riser, it’s moving free but I would call it non operational. I can flip it to either position and it stays. Which way is open?

It is open with the weight down. Check to see if the return spring has failed.

Dave

 

[Jake Fleming]

It is open with the weight down. Check to see if the return spring has failed.

Dave

Yes I figured out if I shut it and start the car it pops to the open position so that’s good. Could be better but not stuck shut.

More update soon and troubleshooting:
I lowered the float level a little, changed the fuel filter, and the air filter it was looking dirty. No effect, still running just the same. I was able to verify that the needle and seat are sealing too

 

[Jake Fleming]

After a little more driving I’m going to say it’s actually notable worse after those adjustments

 

[Davea Lux]

After a little more driving I’m going to say it’s actually notable worse after those adjustments

If it was running too lean, lowering the float will have made it worse.

Dave

 

[Jake Fleming]

If it was running too lean, lowering the float will have made it worse.

Dave

I’m just not sure why it would be lean. I cleaned the carb very well before I reasseembled. Every orofoce was clear. And it’s still clean inside. It’s definitley running rich, if you give it a shot of gas it’ll backfire in the exhaust. I’m suspicious of the power bypass valve, my kit didn’t come with one and it seems work out. Kinda loose. I’m thinking it could be drawing in excess fuel there.

 

[CBODY67]

What you're not seeing is what you're not seeing. Here's why . . .

You cleaned the carb and all of that. BUT . . . inside of the tubes which hang down from the venturi cluster, there can be some accumulated "deposits" in there that the carb cleaner won't remove. Hard deposits. AND, there can be a drilled orifice in the bottom of the idle tubes, called "Low Speed Jet" in the service manual, but you'll probably not find it in a 2bbl carb illustration.

To fix, get a bent wire spark plug gap gauge. Insert the end of the wire into the bottom of the tube, smallest diameter first. Then see how large you can go, in sequence. Then when you get to the largest size, head down to the hobby store and seek "twist drill" assortment to include that size of twist drill bit (and holder).

Use the twist drills to clean the orifice out. Use increasingly larger sizes until you "get brass". Then clean the tubes with spray carb cleaner. Wash it from the top down first, to get any residuals out that way.

This will allow idle fuel to flow from the float bowl upward to the venturi. Adjust idle mixture as desired.

NOW, there's ONE other thing about the Stromberg WWC3 carb. When you take the top off of the carb, check for an imprint in the air horn gasket on the throttle bore side of the float bowl. Especially around the vac passage hole that goes to the power valve plunger (in the air horn). If you do NOT see any imprint there, then the air horn has warped and the power valve plunger is not getting any vacuum to keep it retracted, which means the main system of the carb is "on power mixture" all of the time. In cooler weather, when the choke valve closes enough, it can also such gas from the float bowl into the throttle bores, making for some very rough running until the car warms up enough to come off of fast idle.

To me, the Stromberg WWC3 is a nice-design carb. But like other 2bbls of that era, don't torque the air cleaner wing nut too much!

CBODY67

 

[67Monaco]

I was going argue Physics, 10% ethle fuels, and Stoichiometric ratio's for the whys. But I don't want to get in a pissing contest this morning so I'm just going to stick with it's too lean, be it jets, or vapor forming, or weak fuel pump, and be on my merry way.



Carburetor Tuning: A/F Mixture, Air/Fuel Equation

 

[Jake Fleming]

What you're not seeing is what you're not seeing. Here's why . . .

You cleaned the carb and all of that. BUT . . . inside of the tubes which hang down from the venturi cluster, there can be some accumulated "deposits" in there that the carb cleaner won't remove. Hard deposits. AND, there can be a drilled orifice in the bottom of the idle tubes, called "Low Speed Jet" in the service manual, but you'll probably not find it in a 2bbl carb illustration.

To fix, get a bent wire spark plug gap gauge. Insert the end of the wire into the bottom of the tube, smallest diameter first. Then see how large you can go, in sequence. Then when you get to the largest size, head down to the hobby store and seek "twist drill" assortment to include that size of twist drill bit (and holder).

Use the twist drills to clean the orifice out. Use increasingly larger sizes until you "get brass". Then clean the tubes with spray carb cleaner. Wash it from the top down first, to get any residuals out that way.

This will allow idle fuel to flow from the float bowl upward to the venturi. Adjust idle mixture as desired.

NOW, there's ONE other thing about the Stromberg WWC3 carb. When you take the top off of the carb, check for an imprint in the air horn gasket on the throttle bore side of the float bowl. Especially around the vac passage hole that goes to the power valve plunger (in the air horn). If you do NOT see any imprint there, then the air horn has warped and the power valve plunger is not getting any vacuum to keep it retracted, which means the main system of the carb is "on power mixture" all of the time. In cooler weather, when the choke valve closes enough, it can also such gas from the float bowl into the throttle bores, making for some very rough running until the car warms up enough to come off of fast idle.

To me, the Stromberg WWC3 is a nice-design carb. But like other 2bbls of that era, don't torque the air cleaner wing nut too much!

CBODY67

I think you may have hit on the issue, I always tighten my air cleaner wing nut, kinda a lot. I’ll check for that first, and then if it does appear to be sealing I’ll srop doing that, and move to taking out the venturis and using the twist drill.

I was going argue Physics, 10% ethle fuels, and Stoichiometric ratio's for the whys. But I don't want to get in a pissing contest this morning so I'm just going to stick with it's too lean, be it jets, or vapor forming, or weak fuel pump, and be on my merry way.



Carburetor Tuning: A/F Mixture, Air/Fuel Equation

I’m not looking for a pissing contest, I’m sure you can relate to the frustrations when you think you fixed something and then the problem is still there. I was really just looking for suggestions as to what I could do to correct the lean mixture. I was personally leaning towards rich but I’m not ruling anything out

 

[Jake Fleming]

Ok so the gasket was not getting crushed around the port for that piston so I added a bit of another gasket I had, and cut the thickness in half with a razor, to build up the area a little, but not too much. I also cleaned out the venturis. Then I checked the timing and found it was off. It was right at TDC not advanced, which is odd because I set the timing only a couple months ago. So I reset that to 10* and rebalanced the idle mix with a vacuum gauge. All of this got rid of 80% of the symptoms but it’s still a little off. I may look into replacing the carburetor

 

[Davea Lux]

You might want to check your timing chain while you are at it. An unexplained change in the timing can be an indicator of a loose and failing chain.

Dave

 

[Jake Fleming]

You might want to check your timing chain while you are at it. An unexplained change in the timing can be an indicator of a loose and failing chain.

Dave

Is this an interference engine? And if the timing chain has jumped a tooth then the valve timing would be off right? And no adjusting will fix that