For many years I've often found my car to be rather fume, especially on protracted journeys. Sometimes more so than others. The degree of being fume seems to vary.

I have checked out all the exhaust systems joints which seem fine, with no tell tale grey/black stains where there is a leak.

So, I have therefore decided that the cause must be a fine spray of oil coming from the breather holes in the valve chest cover. The fine spray of oil gets cooked on the exhaust manifold and the exhaust pipe itself, resulting in unpleasant fumes.

Chatting with Ian Moorcraft about this at the Annual Rally last weekend he showed me the system that he has set up to catch this spray of oil. A device that he attaches to the valve chest cover without any need to alter or damage the original valve chest cover itself.

I have taken his idea and rather ploddingly built a similar device out of copper sheet and copper tubing, 15mm and 22mm, plus a brass compression fitting connector.

The cross section area of the 4 holes in the valve chest cover equate to 79 sq mm in total. So care is needed to ensure that at no point is the cross section area of any "escape/drain pipe" less than 79 sq mm. The cross section internal area of 15mm pipe is 84 sq mm.

I cut a cork gasket from a standard valve chest cover gasket and used a few fibre washers behind the 2 standard valve chest "nuts".

The pics, below, show the constructed parts and the device finally fitted.

After a test run, sticking my nose under the bonnet, I'm greeted by "hot engine smell" rather than the fume smell that used to be there.

Now, the next part is to devise a "catch tank" of some sort to catch any oil that comes out of the drain pipe which I have cut short of the chassis cross member.

Location: Bristol

I like that Alastair, nicely engineered modification whilst keeping original components unaltered

Tom

Location: Eye on the Norfolk / Suffolk border

Hi Alistair

Are you using a full sheet gasket which acts as a baffle or just a perimeter gasket? Would expect to be a problem more with the later manifold. I dont recall significant burned oil despite a very ragged engine at one stage which fumed copiously at top speed. Maybe it was spitting out oil which comletely burned on the later manifold! Do you retain the filters at the ends of the valve chest?

Cars using oil may produce a smelly exhaust on overrun which can be sucked inside an open car.

Other makes had similar but with a cover baffle on the inside and usually a downtube outside, ensuring the traditional Brit car oil drip!

What is the experience of others?

Location: Auckland, NZ

HI Alastair,
That is a very wellmade fitting, just a suggestion for the catch tank try using a copper pipe 55 to 75mm about 150mm long blank off both ends fit two 15mm fittings near each end on the pipe on the same plane and one 15mm fitting at a 180 degrees as a drain using a plug,
you can then run this horizontally with the pipe from the cover coming in the top at one end and out the top at the other end as a discharge with a u-bend to point down.
this would look in keeping with the rest of the setup

Cheers

Location: TINOPAI NZ

Hi Bob,

Thanks for your comments/queries.

The valve chest cover is unaltered and behind it I retain the full sheet standard cork gasket which has a number of holes in it. 4 holes. Two of which allow for the studs onto which the knurled knobs screw and the other two which are low down. There is a knack of fitting this cork gasket to ensure that you get a good seal. I leaver the cork gasket up a bit with a screw driver along its bottom edge and at the same time lift the valve chest cover itself up as far as the studs allow and then screw the knurled knobs down.

Not sure what you are referring to when you ask about " ...... do you retain the filters at the ends of the valve chest ? ......"

The engine seems to use little oil.

Location: Bristol

Hi Colin,

that sounds a neat idea. I like the idea of using a large diameter section of pipe for a short run as the catch tank.

At the moment am monitoring it. Not run many miles yet but presently there seems no sign of oil showing at the end of the catch drain pipe. The pipe ends just before the chassis cross member and bends down slightly. It must be a fine mist of oil coming out rather than actual heavy droplets.

Location: Bristol

Hi Alastair

The inserts in the holes each end of block may limit spray from the crank, but I guess most drops come from the cam followers.

My car had a history of short lived mains, attributed to crankcase condensation, so for much of the time I operated with positive ventilation. But when as original and operated very worn with blow by I do not recall any sign of burned oil. Perhaps the cover over the exhaust pipe on RP prevented this. Readers may have views on the merits or otherwise of fitting such to an earlier car if these do not have. May also reduce the fire risk from petrol, a distinct hazard on early cars.

Have others noticed significant oil spray from the vent holes at normal revs?
Leaks from the block but attributed to the cover are the usual experience, or were with paper gasket.

Location: Auckland, NZ