Valve Chest Cover Fumes

[RupertW]

Hello all, 

My 1934 Box is putting out a large amount of fumes from the valve chest cover, to the extent that it is becoming quite unpleasant (and probably unhealthy) to drive even with all windows down/open and the roof slid back. 

Firstly, does the amount coming out indicate an issue with the engine? None of my other 7s kick out anywhere near as many fumes from there, so I suspect there's something a bit off, although it is otherwise driving well. 

Secondly, if I modify the valve chest cover with an outlet pipe to take the fumes away, do I just route it out of the bottom of the engine bay, or is there any other another generally accepted way of routing it? 

Thanks!

["Slack Alice" Simon]

Don't mod your existing cover, there should be ones available from a cherished supplier.   Because every other cover I have come across has been modified, so they must be around.

I have seen the exit pipe lead into the carb, into the oil filler pipe (can't see much point in that!), or down below the chassis.

Said pipe needs to be a reasonable diameter, half inch at least.

Lots of fumes usually means worn bores or rings.   Sudden onset of fumes needs further investigation, otherwise carry on until loss of power/difficult starting/oiled plugs forces a rebuild.

Simon

[RupertW]

Thanks for the reply, it's fairly recently had a new block/rings so hopefully it isn't that, although might it be worn valve guides?
I'd imagine that routing the pipe to the carb would rapidly lead to oily plugs?

[Andy Bennett]

I have understood it to be more about worn valve guides.
I routed mine using a flexi plumbing copper pipe down to below chassis so that it blows away under the car like a second exhaust pipe rather than gets sucked back up.
Andy

[Ruairidh Dunford]

Valve chest fumes, in my experience, as as Andy describes - worn valve guides.

New guides can be fitted with engine in situ.

[Bob Culver]

Significant leakage past rings is usually evident from crank handle resistance and the hissing noise at oil filler. Broken or stuck rings usual culprits. 
Because a cracked block was suspected my car years ago was assembled with .010 bore taper, old type wide rings. Despite this fumes were not evident until a critical high speed over 50 mph when suddenly very evident. In the days when many cars were very worn, I have seen the same effect in other makes.
If the car is burning oil for any reason and exh fumes are being drawn into the car, a very distinctive fumey smell.
We were concerned about crankcase condensation and I ran the car with recon motor for a decade with pipe into the export air filter. Often wonder if it drew too much oil mist from valve chest.
Although performance was otherwise excellent and it used almost no oil my 1960s 1600cc car had excessive blow by for 30 years until recently. The external breather was extended to near road level which largely avoided fumes in the car.

[Hedd_Jones]

I used a bit of 1/2 ID rubber hose when I had such an engine. Zip tied to the chassis. I used it to oil the rear springs. Id swap sides for the outlet every now and again

[Nick Lettington]

My first Ruby blew impressive smoke rings out past the starting handle when the rings broke up!

[Chris KC]

I think I'd replace my valve guides and not mess about with vent tubes. If that doesn't fix it it's something else!

[Hedd_Jones]

if you can find the time to fix it in a few days, or a week great. But if its going to take you 6 months. Fit a vent, blow the smoke out of the back and enjoy the good weather and fix it when its cold and dark in the winter.