Lotus Elan and Lotus Elan Plus 2 Forums

My car has a Weber cylinder head with no breather box, both Miles Wilkins & QED have seen pictures & just agree that it's <another> Lotus anomoly.

Since there is no breather box there is no drain tube from the breather box down to the crankcase under the carbs. When I purchased the car there was a Kent Engine style breather, connected to a rubber hose that just vented to atmosphere:

I have seen these referred to as "Road Oilers"!

So wanting to be a bit more environmentally friendly, i put together with a Burton Breather elbow & a small catch tank:

The catch tank outlet is then connected to the rear of the carb intake housing.

I thought that I'd have to drain the catch tank maybe once per season (approx 1000 miles..) Imagine my surprise when after 100 miles I'm seeing oil coming out of the filter on top of the catch tank & running out of the carb air box. I was expecting oil fumes, not liquid oil to be going through the hose from the crankcase, what am I missing?

The Kent breather you removed is probably baffled inside to catch the oil thrown up from the jackshaft fuel pump lobe, does the Burton elbow have a baffle inside ? Burton also sell a blanking plate with a deflector attached to prevent similar problems occurring with the standard breather system if the fuel pump is removed to fit an electric pump.
http://www.burtonpower.com/fuel-pump-bl ... fp281.html

oldelanman wrote:The Kent breather you removed is probably baffled inside to catch the oil thrown up from the jackshaft fuel pump lobe, does the Burton elbow have a baffle inside ?

No it does not, it's strictly an elbow. I am still using the mechanical fuel pump so I cannot use that blanking plate... thx for the idea though.

If there no Oil separator in your head then the two options would be a external oil separator or find a different breather location.

There various type oil oil separators but there is very little room as they need to be high so they can drain back into the block, i.e. about where the carbs are. So I'd probably do the cam cover breather mod on it and block the hole above the fuel pump. This should give you a fairly oil free breather and nice pipe routing to you catch can.

i would be interested in seeing the pictures of your cylinder head. The oil separator chamber was added during development of the twincam so you must have an early prototype head to not have it. The McCoy Stromberg to Weber head conversions do not have this separator as it is machined off with the Stromberg inlets and they normally use a breather out of the front of the cam cover.

cheers
Rohan

You need to breathe from the topof the engine, if you have no choice but to use the fuel pump breather then use the standard Ford can with the pipe running vertically as high as possible to a catch tank that can drain back down.

Chancer wrote:You need to breathe from the top of the engine, if you have no choice but to use the fuel pump breather then use the standard Ford can with the pipe running vertically as high as possible to a catch tank that can drain back down.

That's exactly what I have just done, created a hybrid of the old & new, with the old separator mounted to the boss above the fuel pump, with a pipe to the catch pot, then venting back to the airbox.

Thx for the confirmation

rgh0 wrote:i would be interested in seeing the pictures of your cylinder head. The oil separator chamber was added during development of the twincam so you must have an early prototype head to not have it. The McCoy Stromberg to Weber head conversions do not have this separator as it is machined off with the Stromberg inlets and they normally use a breather out of the front of the cam cover.

cheers
Rohan

We don't think it is an early head, it does not have the half moons& it was sand cast. Definitely not a converted Stromberg head as the ports are parellel.

The Rear of the head is stamped 9228 & it has F2 stamped on the boss in the spark plug well.

I don't have any good photo's of the head as I have not taken it off, here's the best I have:

pharriso wrote:

oldelanman wrote:The Kent breather you removed is probably baffled inside to catch the oil thrown up from the jackshaft fuel pump lobe, does the Burton elbow have a baffle inside ?

No it does not, it's strictly an elbow. I am still using the mechanical fuel pump so I cannot use that blanking plate... thx for the idea though.

The box looks like the type that has a baffle in it to me? The elbow won't have a baffle in it, but the box should do.

Those boxes usually work with a PCV valve placed in the top and then a pipe from the top of the PCV valve goes to the inlet manifold in a Ford crossflow where the gasses are then burnt through the combustion process.

You could perhaps do something like this with your engine but you'd have to get it to see the right amount of vacuum to work correctly as the crossflow works on a twin choke carb set-up so has all inlet ports sucking from that one point.

You'd still need an additional way of allowing the engine to breathe such as a remote tank with a filter on it.

From my very limited knowledge on engine stuff that looks like an earlier head to me, the lack of lobes, the smaller caps - don?t think it should be on a Sprint. Do you know it?s history?

Cheers

Steve

Hard to tell from the photo but judging by the size of the inlets and the lack of oil KO box i would say its a McCoy conversion. Have you looked under the inlets for the bolts that secure the new manifold to the head ?

The inlet tracts are parallel in the McCoy conversion as the head is machined back to where they are the same as on a Weber head

cheers
Rohan

rgh0 wrote:Hard to tell from the photo but judging by the size of the inlets and the lack of oil KO box i would say its a McCoy conversion. Have you looked under the inlets for the bolts that secure the new manifold to the head ?

The inlet tracts are parallel in the McCoy conversion as the head is machined back to where they are the same as on a Weber head

cheers
Rohan

Absolutely not a McCoy head - I wish it were, this is a McCoy head:



I'll take pictures of my head a little later...

Yes I know..... I think that photo is one of mine !

So if not a McCoy head. and not old. and has big inlets and no oil KO box then what is it and who made it.?

I know QED did a weld on conversion for Strombergs to Webers many years ago but i have never seen one.

cheers
Rohan

Here are some <poor> photos of the head:




You can see the intake tracts are integral to the casting. At some point the carb mounting flanges were removed (to allow porting?) & then welded back on.

This head was on my car when I purchased it 5 years ago & I have no history on the head.

To get back to the reason I posted this topic,& even if it were a McCoy head, is the best way to vent the crank to keep the Kent Oil seperator, Add a PCV valve? & keep the oil catch pot venting to the carb box, or vent the PCV to the carb box?

I'd say keep the kent separator and connect the separator outlet to a catch tank. The outlet of the catch tank can be vented to atmosphere or the airbox / carburettor intake.

The kent type separator was only developed with the later crossflow version of the pushrod engine. Had the Lotus head been developed later they may well have used this separator rather than developing one that was integral with the head.

You don't require a PCV valve because you are directing blowby fumes into the intake of the carburettor or venting to atmosphere. A PCV valve is only required when blowby fumes are being directed after the carburettor/s and into the intake manifold