Breather

[GilsTR]

Watched last weeks subject on the valve cover for the TR3 with interest. I have been offered a very nice alum valve cover...ribbed on top...that has a twist on cap for oil adding...but does not have a breather on it. This very stock engine does have the standard breather tube at the bottom.
Do you think I am getting myself into trouble adding this valve cover WITHOUT the breather on it? I have the usual oil drips below...and am not trying to create any undue pressure in there that would add to this problem! Gil

 

[simpson]

Gil, I bet one could drill the alum cover and fashion an insert/outlet tube to create a breather.

 

[Twosheds]

Gil, are you going to put the valve cover on a TR3?

If so, you don't need a breather in the cover. The oil cap should allow air to enter.

 

[poolboy]

The problem is some aftermarket caps do and some don't from what I've seen.
The road draft tube if kept clean should relieve crankcase pressure, but if the original cap had a vent then I guess the aftermarket should have one, too, even if you have to drill one as "simpson" suggest.

I'm guessing we're talking about a vent hole in the cap and not a nipple on the valve cover itself ??

 

[GilsTR]

This valve cover would be going on a TR3...yes.
The only opening in the cover is for adding the oil...and the cap for it appears to be similar to a radiator cap...thus does not seem to function as a breather. I have checked and the crank breather down below is functing just fine.
Seems that when manufactured if a valve cover breather was not required...the stock cover would not have had one...right?
Like the looks of this beautiful Alum cover...just don't want to get myself into problems! Gil

 

[Twosheds]

The stock TR3 cover has no openings and uses an oil cap with a vent in it. I don't know TR4s, but I think they used a cap with no vent (which sounds like the one you have) and a tube in the cover vented to the intake manifold or somewhere.

If the oil cap you have is similar to a radiator cap, it probably is not vented, like the TR4 cap. I would use a vented cap instead. The stock cap is vented, but won't fit the aftermarket valve covers. I would use a cap like the Mr. Gasket #2061 that Mark Macy sends with the Offenhauser cover. Or just go to your FLAPS and look for one that fits.

I would not drill a hole in a nice valve cover if there is an alternative.

I think the idea is that the road draft tube creates a low pressure area at the outlet as the car goes down the road. This pressure difference draws air in the oil cap, through the engine, and out the draft tube.