TR2/3/3A TR3 "NonBreather" Alloy Valve Cover

[FOG13]

TR3 "NonBreather" Alloy Valve Cover

I purchased an aluminum Alloy valve cover for my 1957 TR3A to replace the original cover. The original has a vented oil filler cap but the new alloy does not. I noticed that the same valve cover for the TR4A has a vent tube on side of cover. Why doesn't the new valve cover have a vent and is my engine subject to damage because of pressure build up?

 

[Banjo]

Re: TR3 "NonBreather" Alloy Valve Cover

I believe all the Aluminum valve covers come without the vent hole in them. this allows the purchaser to locate the hole for whatever needs thier application has, or not have one if other provisions for venting have been made.
You do need to have a vent. otherwise the gases will collect in the sump, and will lead to problems. Generally, on a TR3 the fresh air is pulled in the filler cap, and the gasses are pulled out semi-venturi-style at the road draft tube.
either drill a hole and fit a breather filter, or find a vented filler cap that will fit.

 

[prb51]

Re: TR3 "NonBreather" Alloy Valve Cover

Fog,
You'll probably notice the very small vented twist on cap that came with the alloy unit. It does allow some venting but obviously not as much as the original.
I ran mine (56 TR3) for some time with that cap (didn't notice any issues) but eventually welded an alloy pipe the size of the old vented cap in place and run the original cap instead.
I just couldn't see how the pinhole vent could work in the manner the original was designed to do.

 

[Mkutz]

Re: TR3 "NonBreather" Alloy Valve Cover

I've been pondering a similar question. I have a TR4 engine in my 3 and when it was rebuilt I had the draft tube installed in the side of the block as it should be. Only problem is the filler cap...the breathable filler cap for a Tr3 was originally a push on design, but I need something that is screw on and breathable. Anyone know a suitable replacement?