Lotus Elan

Oil breather

PostPost by: nickspeed » Sat May 23, 2020 8:26 pm

Recently bought an Elan S4. Checking it over, discovered that there is a rubber hose pushed on to a plastic connector, and in turn the connector is pushed in to the 90° rubber elbow pushed in to the side of the head, that acts as the oil breather. The plastic connector is very small and the hose has a very small ID. Think it's fuel hose. Have bought a metal breather tube from Mick Miller. One end has metal mesh inside, and the other end has an external bracket. The end with the mesh pushes in to the rubber elbow? And the bracket on the other end fixes on to the gearbox casing? Or is it the other way round? Will the mesh clog up with coagulated oil in time? With thanks
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PostPost by: SENC » Sun May 24, 2020 12:48 am

Pictures would help make sure we're answering correctly, but...

early Elans had the rubber elbow and a road draft tube that vented to the atmosphere below the car

S4s had a pipe from the hole to the airbox, using the manifold vacuum to pull crankcase gases. I suspect this is what you purchased. They are different for the Stromberg airbox than for the Weber airbox.

Many have re-routed to catch-cans. I've gone back to the road draft tube for the moment.
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PostPost by: nickspeed » Sun May 24, 2020 5:52 am

This is as it is with small plastic fitting and 'petrol hose'
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PostPost by: SENC » Sun May 24, 2020 11:50 am

Originally, that elbow would have had a (larger ID) tube that terminated to the atmosphere alongside the sump, so that forward momentum of the car created a bit of venturi vacuum.

By the time our S4s were built, they had rerouted to airboxes for vacuum and to let the engine burn off the gases rather than send them straight to the air. The elbow is not used in this setup.

Mine has Strombergs, and there is a hole in the airbox behind the #4 carburetor where the tube I suspect you have purchased fits. Yours may be a Weber - I think the concept is the same but the tube different.

Here are a couple links that might be useful:
viewtopic.php?f=40&t=45389
viewtopic.php?f=40&t=26690&start=
viewtopic.php?f=40&t=28987&start=
Last edited by SENC on Sun May 24, 2020 12:58 pm, edited 1 time in total.
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PostPost by: 1969Plus2 » Sun May 24, 2020 12:41 pm

The wire mesh won’t clog.
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PostPost by: nickspeed » Sun May 24, 2020 3:44 pm

That's very helpful, thank you! I've looked through the links. My S4 is on Strombergs but the guy who rebuilt it decided to let the breather run to ground, rather than to the airbox. The problem is that he's used a plastic fitting with a very small ID, and then petrol hose, which again is very small. The compressions are good on all cylinders - around 200psi - but the engine has done few miles since a rebuild, and at present there is some blow past, which in turn is blowing vapour out of the dipstick. And I think part of the problem is the restricted breather. The photo - which I'll try to post with this - shows the breather tube I sourced from Sue Miller, lying across from the cam cover to the airbox. Now I think from the length and shape that this is intended to run from the head, down the side of the bell housing, with maybe some additional rubber hose on the bottom to allow it to vent under the car. Don't think the tube is intended to go between the head and air box
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PostPost by: pharriso » Sun May 24, 2020 4:12 pm

Yes, that looks like the S1 pre-emission laws road oiler setup!
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PostPost by: SENC » Sun May 24, 2020 4:13 pm

Nick - that pipe will fit between the head and the airbox, but without the elbow. You do need a grommet on the head side, as I recall.

The downside to this arrangement is you will get some oil mist through to the airbox that will tend to get ingested in the #4 carb more than the others and is often blamed for fouled plugs.

When I rebuilt my carburettors last year, I opted for the elbow and a tube to the ground. My first test was with a fuel pipe, too, but as you experienced I was clearly building up pressure in the crankcase that was coming up the dipstick and weeping at the cam cover bolts. For a second test I found some clear vent tubing that fits over (rather than inside) the elbow, and also made sure it dipped into the slipstream below the car. The combination of more capacity and a little venturi effect solved my problem, and judging by what I see in the clear tube I'd guess mostly blowby gasses and little oil is escaping. I haven't got around to a more permanent pipe, but thinking this is what I'll do.
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PostPost by: oldelanman » Sun May 24, 2020 4:25 pm

Here's the tube installed on my Stromberg S4
IMG_20200524_170250.jpg and
loop
IMG_20200524_170202__01.jpg and
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PostPost by: h20hamelan » Sun May 24, 2020 4:27 pm

Some vehicles. I plumb the cam or crank vents to the exhaust. So they get burnt, mostly. Doubt they all get burnt. I weld a o2 bung which doubles as a port for putting a sender for a removable metering device.
After done with the o2. Replace the sender with barbed end with vent hose.
I use a universal flame trap/arrester. But it seems the venturi of the exhaust pulls the fumes well enough.
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PostPost by: 1969Plus2 » Sun May 24, 2020 5:34 pm

Looks like you have all of the parts required to connect it to your airbox. If you need replacement grommets you can get them from rd enterprises.

I like venting to the airbox since there is always some vacuum and reduces pressure in the crankcase.
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PostPost by: RichardHawkins » Sun May 24, 2020 8:01 pm

Nick,

Although my car is an early S4 I was surprised to find it had a draft tube rather than a connection to the air box. Of course I don’t know if this was original or the work of a previous owner.

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PostPost by: nickspeed » Mon May 25, 2020 11:09 am

Thanks one and all! The pipe I sourced is 18 in the drawing below, whereas what I would like is 17, venting to ground. Matty's show it on their parts list, but as to whether they have one ....
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PostPost by: nmauduit » Mon May 25, 2020 11:47 am

nickspeed wrote:Thanks one and all! The pipe I sourced is 18 in the drawing below, whereas what I would like is 17, venting to ground. Matty's show it on their parts list, but as to whether they have one ....


I have a tube "17" somewhere (...) : it's just a tube with a couple tabs, should be easy enough to make...

I won't use it as I don't facy oiling up the road or track more than it already is ... and mostly I like to see what gets out to monitor the internals of the boiler, so a catch tank makes sense for me.
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PostPost by: nickspeed » Mon May 25, 2020 12:07 pm

Yup, true, a catch tank may be the way to go - possibly mounted in front of the radiator? Does anyone recommend a proprietary tank. As a newly restored car the engine bay is pretty smart, and I wouldn't mind spending on a nice tank
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