Dumb Rookie Question re: Air Filters

[ChrisMinelli]

Hello,

 

I’m 2 parts rookie and 1 part dummy, and last weekend I cleaned my oil bath air cleaner for the first time.  I reinstalled it and couldn’t get the engine to idle right to save my life.  When the automatic choke was on it sounded fine.  Otherwise, when the engine came up to temperature it sputtered and ran rough.  The idle adjustment and mixture screws did literally nothing on the carb. 
 

I was tinkering with it tonight and when I loosened the oil bath’s bottom twist screw the car startled idling like new.  Both carb adjustments worked properly.  
 

So I must have been doing something wrong:

 

1. Does the oil bath filter need to be tightened to the carb, or is it just a “little” snug with the heavy lifting occurring with that 1/2” bolt on the side?

 

2.  My oil bath filter does not have any sort of gasket between it and the carb.  Is this correct?  It sits metal to metal.  
 

3.  The oil bath filter just sits on the top of the carb, correct?  It doesn’t snap down or otherwise connect to the carb save for the twisty ring’s squeezing pressure?  (Technical term)

[BobT-47P15]

WELL.....I don't see a gasket between air filter and carb in this pic from the P15 parts manual.  And I do not have one on 47 P15.

Yes....you tighten the air cleaner to the carb by turning that nice big "key"  that you see.

There is also a flat bar brace that bolts to the driver side of the air cleaner and then to the head to steady the cleaner.

 

And did you put some motor oil in the bottom of the cleaner to catch dirt?   These old cleaners work pretty well....have never had a problem

with mine.   Some people have modified their housing to accept a paper filter. 

 

Pic from Parts Manual......

 

 

   

[MarcDeSoto]

There definitely is a gasket between the carburetor and the oil bath air cleaner for all 1940s MoPars. It's a kind of thick heavy type gasket that sits at an angle if I remember.  I'm looking at a P-15 Parts List under the Fuel section.  Under Air Cleaner it says GASKET, Air Cleaner to Carburetor,  Part no. 952062.  I've been around these cars for 40 years and gaskets are required.  Many cars are missing it just because someone didn't put it back on after removing the air cleaner.  

[MarcDeSoto]

Looks like that gasket is available on Ebay.   It's just $4.84 and free shipping.  

 

 https://www.ebay.com/itm/NORS-CARBURETOR-AIR-CLEANER-MOUNTING-GASKET-1942-1961-DODGE-PLYMOUTH-1556663/113929378327?hash=item1a86b85a17:g:mNMAAOSwfOBdqzR8

Edited March 25, 2021 by MarcDeSoto

[maok]

I would guess that you have inadvertently caused a huge air blockage in that air filter when you clean it out.

[JBNeal]

9 hours ago, ChrisMinelli said:

...

2.  My oil bath filter does not have any sort of gasket between it and the carb.  Is this correct?

...

 

additional information - air filter gasket replacement

 

When ya say you cleaned the air cleaner, what method did ya use?  ?

[Marcel Backs]

Where I am located, the roads are a lot like what they were in the the 30s and 40s. I do run some gravel and it can get dusty. As suggested above it is possible to put a paper element filter in place. A washable low restriction filter like a k and n would be quite a bit more effective than the old style one. Anyone with an original filter canister modded to accept a paper element handy, please post it if you can. This is a mod that I would like to check into. I have looked for a paper element filter that would be a direct fit, but no success. Has anyone had any success with  this approach? M 

PS thanks for mentioning this mod Bob T

[TodFitch]

35 minutes ago, Marcel Backs said:

Where I am located, the roads are a lot like what they were in the the 30s and 40s. I do run some gravel and it can get dusty. As suggested above it is possible to put a paper element filter in place. A washable low restriction filter like a k and n would be quite a bit more effective than the old style one. . .

I beg to differ.

 

The washable oil bath type filter is very good at capturing road dust before it gets into the carburetor. In fact, for years after paper filters came out the factory still used the oil bath filters for heavy duty and dusty location applications.

 

The main advantage of the paper element filter is that it is quick and easy to change. And the service department can charge a pretty penny for putting in factory approved service parts.

[ccudahy]

Just thinking out loud!?... Could the running rough issues be caused by a bad manifold/carb gasket, loose carb at base, or loose carb at the halves?  With all the jostling around created a vacuum leak putting the air cleaner on. Then the second time putting air cleaner back got everything set back to a better position? Would it not hurt to check if everything from the manifold up is tight? Had a Slant Six went you put the Air Filter on you could change the setting the carb halves were warped so bad.

[ChrisMinelli]

To answer the question -- I cleaned the air cleaner the way the service manual suggests.  I took it off the carb; I drained the old oil out and cleaned it; I soaked the top part in solvent; I put SAE 30 back into the base (yeah I know it says SAE 50 but I'm not paying for racing oil for an oil bath); and then put the assembly back on the carb.

 

So to gather from your comments: there may or may not be a gasket between the air cleaner and the carb.  Mine did not have one, and it is running differently pre-clean (no gasket) and post-clean (also no gasket) so I'm thinking the gasket is not the issue even though it may be a good idea.

 

I'm thinking maybe the cleaning did restrict air somehow.  I'll look into that tonight.

[ChrisMinelli]

2 minutes ago, ccudahy said:

Just thinking out loud!?... Could the running rough issues be caused by a bad manifold/carb gasket, loose carb at base, or loose carb at the halves?  With all the jostling around created a vacuum leak putting the air cleaner on. Then the second time putting air cleaner back got everything set back to a better position? Would it not hurt to check if everything from the manifold up is tight? Had a Slant Six went you put the Air Filter on you could change the setting the carb halves were warped so bad.

 

That's a great idea -- I was moving the carb around quite a bit to get the thing off.

[Merle Coggins]

9 minutes ago, ccudahy said:

Just thinking out loud!?... Could the running rough issues be caused by a bad manifold/carb gasket, loose carb at base, or loose carb at the halves?  With all the jostling around created a vacuum leak putting the air cleaner on. Then the second time putting air cleaner back got everything set back to a better position? Would it not hurt to check if everything from the manifold up is tight? Had a Slant Six went you put the Air Filter on you could change the setting the carb halves were warped so bad.

 

That was my though too. Having the air cleaner tight to the carb must have disturbed the base gasket, if loose. Loosening it up allowed it to settle back down. 

 

And YES, there should be a gasket between the air cleaner and the carb flange. 

[JBNeal]

SAE 50 is required for good reason, as it is heavy enough to not slosh around onto the engine but light enough to capture air contaminants.  I have used store brand SAE 50 for decades for this purpose, which is much cheaper than racing oil.  Overfilling the housing will restrict air flow through the cellulose membrane, as it only should act as a wick of sorts to drain contaminated oil back into the sump.

 

The base gasket also helps the clamp secure the housing to the carburetor, eliminating most vibrations caused by the engine.  Excessive vibrations, especially if the sump has too light of oil, will cause too much oil to migrate into the cellulose membrane, which will restrict air flow into the carburetor.

 

One thing to look at is the throat of the carburetor...if it is too oily, then too much sump oil is getting through the cellulose membrane.  Normal is to wipe your finger around the throat and have a pencil lead width line of oil present...if the throat is wet with oil, that's a problem.

 

This seems like a lot of work, but I can tell you that my only air filter costs since initial startup is buying a quart of SAE 50 at Advance Auto every 3 years or so...a trick I learned was to drain the sump oil into a clear glass jar every spring until I could see crud flowing out...whatever oil was in the sump then was used to resurface the end of the driveway, so roughly the top half of the sump oil was clean enough to reuse.  Since this wasn't a daily driver, this worked out well, and I could spend my savings on a trip to Dairy Queen ?

[Merle Coggins]

I believe 80 or 90 gear lube has approximately the same viscosity as 50 engine oil. Gear lubes are rated differently than engine lubes, hence the difference in numbers. Why wouldn't gear lube work in the air cleaner? 

[Sam Buchanan]

My Local Walmart has Castrol GTX 50W on the shelf.

[maok]

Also, is it possible that you have a hole in the cleaner, so oil maybe going down the carb?

[JBNeal]

3 hours ago, Merle Coggins said:

I believe 80 or 90 gear lube has approximately the same viscosity as 50 engine oil. Gear lubes are rated differently than engine lubes, hence the difference in numbers. Why wouldn't gear lube work in the air cleaner? 

I believe the problem with heavier oils is that they have higher surface tension, causing them to more readily cling to the cellulose membrane and basically ball up, which can cause too much airflow restriction.  SAE 50 is suited for this task since its lower surface tension allows it to drain back from the cellulose membrane faster than gear oils, especially in colder weather.

[DJ194950]

My oil filled air cleaner has a mix of high quality 60wt. and 20 wt. oils as I had both here and no current use for either.??

 

Working fine except when I removed the air cleaner and fumbled it spilling a bunch of oil on the cleaner and motor/floor as I needed to remove carb again after a couple years of the car just sitting/ ran occasionally but not driven.   ?

 

DJ

[ChrisMinelli]

Does anyone have the OD and ID of the proper gasket?  I ended up ordering one on eBay but I want to make a temporary one for this weekend out of cork.  Thanks in advance!

[JBNeal]

asked and answered 

[Young Ed]

One thing I didn't see mentioned- make sure the clamp for the oil bath isn't interfering with the carb mechanisms.