Non vented oil filler cap

[bkahler]

Anyone know of a source for a non-vented oil filler cap.  The tube diameter is 1.5" OD.  

 

I've been searching for a while but so far haven't had any luck.

 

Thanks,

 

Brad

[JBNeal]

How'bout sealing off the vented cap you have?  A simplistic approach is to stick a cork in your fill tube and use your cap as its retainer.  Another approach is to take the bottom of a coke can and peen it over the oil fill tube instead of using a cork, making it the functional sealing cap and the vented cap is its more aesthetically pleasing retainer.  I've heard of vented caps being sealed off with aluminum tape then rattle-canned over as needed...many possibilities that can be pursued without switching out the oil fill tube for one of the Power Wagon sealed cap assemblies

[bkahler]

Ok, you got me thinking now

 

I had it in my brain that all of the holes on the outside would need to be covered for it to seal, however like you suggested, just plugging the two slits on the inside would solve the problem.  Not sure why I didn't realize that earlier but I didn't.  

 

It would appear that a piece of rubber stuff up inside the cap would solve the problem.  I wouldn't want to use cork for fear of cork pieces breaking off and falling into the oil pan.  Time to find some rubber......

 

Thanks!

 

Brad

 

[bkahler]

Well, that was just too easy (and cheap!).

 

Thanks for the idea JB

 

 

Edited November 10, 2020 by bkahler

[JBNeal]

There was a discussion years ago regarding this part of a PCV conversion, as some folks were adamant that the oil fill tube had to be perfectly sealed in order for that part of the circuit to work, based on what was done with the Power Wagons.  I argued that perfect seal had to do with not allowing water to get into the crankcase when fording a small river, but this point fell onto deaf ears.  The crankcase cap in question was the same replacement style as yours, and it had been sealed with a flat tin donut epoxied over the intake holes of the cap, but it only had the metal-to-metal seal of the cap over the fill tube.  When I pointed out that was more of a severe restriction than a true watertight seal, it kinda set a few ppl off, but that's another story...bottom line was that as long as that fill cap allows for crankcase fumes to be drawn into the charge air stream instead of the engine compartment, then the "sealed" cap has served its purpose

[bkahler]

33 minutes ago, JBNeal said:

There was a discussion years ago regarding this part of a PCV conversion, as some folks were adamant that the oil fill tube had to be perfectly sealed in order for that part of the circuit to work, based on what was done with the Power Wagons.  I argued that perfect seal had to do with not allowing water to get into the crankcase when fording a small river, but this point fell onto deaf ears.  The crankcase cap in question was the same replacement style as yours, and it had been sealed with a flat tin donut epoxied over the intake holes of the cap, but it only had the metal-to-metal seal of the cap over the fill tube.  When I pointed out that was more of a severe restriction than a true watertight seal, it kinda set a few ppl off, but that's another story...bottom line was that as long as that fill cap allows for crankcase fumes to be drawn into the charge air stream instead of the engine compartment, then the "sealed" cap has served its purpose

 

I would think as long as the volume of air being sucked in by the carburetor exceeds that which can flow through the cap seal then all would be good.  The rubber seal I used was large enough that it presses down on the top of the tube creating what I would consider a pretty decent seal.  You can see in the picture below the rubber has indentations from the top of the tube.  I believe that's a pretty good seal

 

 

 

[kencombs]

Of course the ideal is to use the carb air filter as the admittance point. At least the industry settled on that as a standard, so at least it works, if not ideal.   Seal the oil fill, add a tube from the oil fill tube to the carb air filter, after the filter element.  I'm of the opinion that most carb filters catch smaller particles that that mesh in the original filler cap.

 

Of course that means adding a connection to the filler tube, but a simple hose nipple brazed or soldered in place after drilling the needed hole is easy.

 

I'm investigating a screw in PCV valve from an early Chevy V8 with PCV.  Maybe add it to the intake manifold, or my 2 bbl carb adapter.  I think a hard line from the draft tube location to the intake can be added neatly, much better than hoses IMO.  The reason for the 'foreign' valve is the flow is reversed when screwed into the manifold rather than the block.  I just need to see if the open/close vacuum specs are near the the flatheads needs

 

 

[bkahler]

What you've described is pretty much what I've done.

[MBF]

I modified the road draft tubea on my 2.5 on.  I cut it off at the fitting and welded a nipple on the end.  That nipple has a hose with a PDV valvle in it going to a vacuum source on the intake manifold.  The sintered oil cap was replace with one from an early slant six that also had a nipple on it.  I ran a hose from the fill cap to the air cleaner to hopefully assure a cleaner source of air for the crankcase.   So far, so good..........  to be continued..