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MG MGA - Alloy Rocker Cover-Breather Connection

Just bought a Ribbed Alloy Cover and find no breather connection on the unit. Do I just drill,tap and fit a threaded connection for the hose n the non-ribbed ends of the cover or...?? Would be grateful if the wise out there in the ether could advise best approach??
neil ferguson

Breather should be located on or near top of cover. There should be a baffle inside to prevent oil from splashing from rocker arms directly into the breather port.
Barney Gaylord

The cover may well have a cap that has a breather facility instead of using a separate hose connection. Or it may have no breather facility at all which makes your modification essential.
dominic clancy

Neil, I selectively ground down the ribs in a location similar to the original. Then I drilled and tapped for a brass barbed fitting. I use the std rubber vent tube to the filter box. An internal baffle would be good, but so far, it seems to not need one.

Chuck Schaefer

Guys..many thanks for advice. Have now read up just what the breather does and will drill,tap and fit a connection. I note all the alloy covers sold on various sites do not have the breather connection...are these people who make these ( and mine ) from another planet?
neil ferguson

I'm not an expert on this, but my motorhead friends at work thought that a properly vented oil filler cap with an integrated filter would provide the same benefits as the breather tube/air filter route. I ran for several years with an Edelbrock cap/breather and an alloy valve cover with no perceived problems. I've switched to a Judson supercharger now, which has an integrated alloy valve cover / supercharger oiler. I am using the same Edelbrock cap/breather on my system now, which I have been running for 4 years now. Am I causing any potential future problems for my engine by running without the breather tube to air filter connection ?

Chuck Mosher

Chuck Mosher

Is there any benifits to fitting an alloy valve cover other than cosmetic ? thanks Sean
S Sherry

Mostly for appearance only. It is a valid period accessory, but then so are fuzzy dice, fox tail on the antenna, and white wall tires, none of which make the car go any faster. Original character of the car is "no frills" until you start playing with accessories.

The alloy valve cover can reduce tappet noise slightly (taking away a bit of original character from the car). It can achieve a leak free bottom gasket joint (with due care and attention). However, many alloy covers are flat on bottom with no alignment lip for the gasket, making it a royal PITA to keep the gasket aligned during initial fitting. I have seen more leaks caused than cured this way. I don't see that as much of an advantage when it is possible to have a leak free original type cover.

A well vented and filtered oil filler cap (big lump) can provide proper crankcase ventilation, but it is prone to dribbling a bit of oil onto the rocker cover. The later model MGB "vented" and filtered filler cap is intentionally restricted and does not have enough vent flow capacity to do the job with the draft tube vent setup.
Barney Gaylord

The chrome filler cap that came with my alloy valve cover was vented. It has a very small hole for this. The cover is probably more for a MGB venting system rather than the MGA. As Barney said, it is nowhere near large enough to allow enough air flow in an "A". I ran for several years without the added vent tube and ALWAYS had oil seeping OUT of the filler and onto the cover. Once I installed the vent tube, the cover has remained dry.

I had originally had problems fitting the valve cover gasket to my car. The valve cover nuts were too short and the added height of the gasket would not allow enough threads to engage. I removed the gasket and have used just silicone gasket maker. No problems.

I installed the alloy valve cover when I built the engine to help reduce the sewing-machine-like sound of the valve train. It does help some, but not enough to cause me to do it again. I could care less about the "bling" factor. I have kept the original valve cover somewhere for the next owner.
Chuck Schaefer

> However, many alloy covers are flat on bottom with no
> alignment lip for the gasket, making it a royal PITA
> to keep the gasket aligned during initial fitting. I
> have seen more leaks caused than cured this way.

The alloy cover on my car always leaked a little, and I finally discovered why when I had the engine apart and really examined the situation. The shape of the cover doesn't even exactly match the standard gasket, in that the gasket is more square at the corners, making it difficult to force a leak free fit. I want to retain my dad's cast, finned cover, so I am going to end up making my own gasket out of thick cork gasket material to provide an exact fit.

For a vent, the side of the cover has been drilled and tapped for pipe threads, with the stub of a steel pipe threaded in to provide a location for the hose to attach. My dad probably did that 45 years ago, and it seems to work okay. There is no baffle or anything like that. I'd be extremely cautious installing anything like that on the inside of the cover, because it could potentially come off and get into the moving parts. Certainly, if you install any sort of baffle, make sure that it and whatever you use to install it are made out of soft aluminum, so that hopefully the valve train components will win any conflict that may occur later.
Del Rawlins

Attached photo shows my setup. I used 1/4" brass pipe since it is a tight slip fit inside the breather tubing. The hole in the valve cover is tapped and sized such that the pipe screws in almost all the way. Inside the valve cover is a fabricated baffle that fits over the pipe and is secured by a threaded jam nut.

How does it work? In this photo, the hint of orange inside the air cleaner is the rubber portion of a Fram filter. I went back to standard screen filters after the Front Fram Filter (say that ten times fast) plugged up due to oil mist. Since then I've added the baffle but, as I still run the mesh filters, I don't know if I've fixed the problem. Hope this helps,

Bill Eastman

This thread was discussed between 17/10/2009 and 21/10/2009

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