Fixing up a cam cover; please help me understand breathing

[govmule84]

Hi.

I'm working on a Big Twin cam cover. ('37-'39 because the outside is not ribbed, but I think these are all functionally the same.)

I need some help. This cover had a bad flutter valve. I got that out. It also had a busted pin for the oil seal ring (585-37).

I have some questions. First, do I need both of these parts? It seems like they're performing the same function, but I'm guessing they're both necessary. I just don't know why. I have a very nice Flathead Power reproduction cover that is (I think) ready to run after reaming, but I see no provision for a flutter valve on it. Is the FHP cover just made wrong, or are these parts redundant? Is the flutter valve venting the crankcase and the oil seal ring venting the cam chest?



Secondly, are there any tricks to installing this flutter valve? I had to heat my cam cover to drive the old one out, and it was staked over. Is this a simple follow the manual, "line it up and bang into place" operation, or is the aluminum likely to now be hogged out?

Thirdly, on the same cam cover, that oil seal ring... what's the hot ticket for getting the pins in place correctly? Just line everything up and smash 'em in, or is there a better way? My manual doesn't even mention this thing, I don't think.

Thanks in advance.

[kitabel]

Oil naturally accumulates inside the cover casting since it's pressurized by the pump. The valve opens in response to crankcase vacuum and draws oil out of the cover. If the oil gets too high it comes out of the standpipe.

[govmule84]

Oil naturally accumulates inside the cover casting since it's pressurized by the pump. The valve opens in response to crankcase vacuum and draws oil out of the cover. If the oil gets too high it comes out of the standpipe.

Just the man I was hoping would chime in.

I think I understand that concept; the flutter valve acts as a PCV valve, if I get the idea.

If that is the case, what the hell is the oil seal ring for? I assumed because it is in the path of the standpipe breather area of the casting that it's related to oil, but maybe I'm wrong. What's that little spring-loaded tin piece for? A buddy told me it has something to do with holding the genny gear on, but the 32E I have off a different bike has a gear that's pinned in place. It's also highly likely I'll use a 65A genny on whatever motor this cam cover winds up on.

I don't mind installing a butterfly valve on both of these cam covers and a fresh oil seal ring on the original one, but I don't want to bother buying and installing parts that I don't necessarily use.

And finally, why the hell is there no provision to put a butterfly valve in this reproduction?! It also seems to have problems accepting the tapered needle for the chain oiler. Starting to really not trust it.

[Rubone]

The seal ring fits against the slinger on the generator gear. The slinger is an air/oil separator that causes oil vapor to collect and then excess liquid material is thrown off. The sleeve on the seal ring is to direct the then "mostly" oil free air into the breather cavity. As you surmised the flapper valve is designed to drain any excess oui in the baffle chamber back into the crankcase. Without it there is a pulse back into the chamber on every stroke cycle which tend to prevent complete draining as it is blowing cam chest pressure back up the baffle chamber.

[Sargehere]

I don't mind installing a butterfly valve on both of these cam covers and a fresh oil seal ring on the original one, but I don't want to bother buying and installing parts that I don't necessarily use...

It's much more than a PCV valve, Governor,
You're basically over-thinking this whole thing. William S. Harley never included parts in the MoCo's motor design that you won't necessarily use. You see all the leetle holes around the rim of the Flathead generator gear? They're a centrifugal oil separator provided that allows the lower end, under the pistons, to breathe. Literally.
The design uses the changing air pressure from the rising-and-falling of the pistons to urge the oil through the bottom end, and past the "scraper." No matter which electrical generator you use on your Flathead, use the slinger gear. It's a necessary feature of the engine designed to keep the oil on the inside.
As the pistons fall, oil that's been centrifugally-flung onto the crankcase scraper is pushed back through a hole into the cam chest near the oil pump, making its way by gravity down to the breather valve and the return oil pump. The engine does this rather inefficiently, and excess lower-end air pressure is relieved (out of the engine) on the pistons' downstroke, and alternately drawn in as the pistons rise, all through those little holes in the generator gear. The holes separate the oil passing through it from the air, keep most of the oil in the engine, and vent the engine lower end air pressure to the atmosphere. The brass spring plate serves as a lubricated seal on the face of the slinger gear to insure returning oil goes through those holes, and gets slung centrifugally back into the engine, separated from the air.

[govmule84]

OK, so it sounds like the general consensus here is that I need to replace the oil seal ring on my OEM cover and the butterfly valve, and then I need to drill a larger hole and hit it with an endmill on my repop to accommodate a butterfly valve, right-o?

Can anyone give me any guidance on replacing the seal ring and pins? I'm not a hundred percent clear on how I drive such a small diameter, big length pin in without bending it... I'm assuming there is a special tool to do this that I don't know about. My (very, very) old manual gives no insight here that I can find.

[Sargehere]

Can anyone give me any guidance on replacing the seal ring and pins? I'm not a hundred percent clear on how I drive such a small diameter, big length pin in without bending it...

Very, very carefully. You can see what's required.
I'm amazed at how Harleys got repaired all across the fruited plain in the first decades of the last century; there was not even a formal service manual until 1940. The factory had a resident Service School, but was still dependent upon word-of-mouth, informal on-job-training at mom-and-pop franchises in every town with more than one horse. Take your time, & good luck!

[1950Panhead]

Can anyone give me any guidance on replacing the seal ring and pins? I'm not a hundred percent clear on how I drive such a small diameter, big length pin in without bending it... I'm assuming there is a special tool to do this that I don't know about. My (very, very) old manual gives no insight here that I can find.

Did the original pins come out in one piece or did they break in the cover ?

[govmule84]

Did the original pins come out in one piece or did they break in the cover ?

I received the cover with one pin missing totally, and one broken off flush with the surface of the cover.

[41craig]

I replaced the breather valve on my ULH many years ago. You just place the new one in the cover and make sure that it bottoms out in the cover. Then just stake it with a punch.
Craig

[govmule84]

I replaced the breather valve on my ULH many years ago. You just place the new one in the cover and make sure that it bottoms out in the cover. Then just stake it with a punch.
Craig

OK, cool. That's how I thought that got handled. That's easy enough. Now I just need to figure out the pin thingers on the oil seal jibbler.

[41craig]

Your first problem will be removing the broken pins. Once removed, check the fit of your new pins in your cam cover. They are an interference fit. If the holes are too large now ( but not wallowed out ) take a scribe or similar small object and upset the hole a bit, so that your pins will go in with some resistance.
Craig

[govmule84]

Your first problem will be removing the broken pins. Once removed, check the fit of your new pins in your cam cover. They are an interference fit. If the holes are too large now ( but not wallowed out ) take a scribe or similar small object and upset the hole a bit, so that your pins will go in with some resistance.
Craig

The broken pin is out. Hole feels about the same as the other when I slide a 5/32" punch in there, but my thought was to repair this by drilling a little larger, threading a bolt in, cutting it off, then drilling my effective steel insert a touch undersize.

I also have it from a reputable flathead tech that these are commonly removed for race use, so I may attempt to replace the flutter valve, run this cover, and see what problems (if any) I face running in that fashion. To be honest, I hate the idea of delicate tin and a spring and two weak little pins just waiting to exit in service.

But this is good stuff; exactly the advice I seek.

[1950Panhead]

To be honest, I hate the idea of delicate tin and a spring and two weak little pins just waiting to exit in service.

I have never seen the little pins exit service prematurely, go wild and use 6/32 (.187") pins

[govmule84]

I have never seen the little pins exit service prematurely, go wild and use 6/32 (.187") pins

I would be making them, I guess. I am not aware of o/s pins, but if they exist, I would love to find a set!