Lotus Elan

Getting rid of the cranckase fumes in the air box

PostPost by: Pistacchio sprint 72 » Tue Jul 23, 2013 1:33 pm

My airbox was so dirty inside yesterday that I close it back. :shock:

I would need at least a full can of brake cleaner to clean it properly and get rid of all the layers of dry greasy oil in it.

I don't want the cranckcase excess pressure to blow oil mist in my carb box. :?

I know Clive's product and I have seen the picture ( he is out of stock) but do you guys have done other mods to blow the mist down the road and closing the air box?

I would be interested to know. Thanks

PS I also notice I had no gasket in my air box.... :roll:
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PostPost by: Pistacchio sprint 72 » Tue Jul 23, 2013 1:42 pm

Is one item on this list could be useful for my purpose???

I don't even recognize the parts!

http://www.burtonpower.com/catalogsearc ... m+breather
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PostPost by: billwill » Tue Jul 23, 2013 2:32 pm

The original engine had a simple tube that blew the fumes down onto the road at the back of the bell housing this grommet from that Burton list above is the necessary right angle bend.
Image

However this was considered too polluting and so the air box suck was devised. The theory is that the fumes are burnt in the engine and that is less polluting. (?).


I am trying out a new arrangement made from common 15mm copper plumbing fittings.
lotus-elan-f19/getting-ogu-roadworthy-again-t26101-75.html#p176701
It is intended to drip into an aluminium drinking flask which is fastened to the block where the old mechanical fuel pump used to be. As it is underneath the rear carb, I will need a turky baster tool to suck up any oily grunge that collects in the flask.

This is highly experimental so try at your own risk... It may make more sense to have a long flexy pipe on the end to pipe the oily gunge to somewhere more suitable in front of the radiator.

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PostPost by: RogerFrench » Tue Jul 23, 2013 4:03 pm

It's a relatively easy matter to rig up a catch-can like billwill shows above - you can even buy them with drains if the turkey-baster doesn't appeal to you.

On the Burton page you show, the top item is the grommet that fits into the cylinder head - you can see it in place on billwill's photograph. The middle item fits between block/crankcase and cylinder head, just underneath the grommet, and the bottom item is for older engines, instead of the grommet, where fumes were led directly to the atmosphere.

It has been standard practice for many years, among all car makers, to re-breathe internal engine fumes - more lately via PCV valves (see http://autos.yahoo.com/maintain/repairqa/engine/ques079_1.html ) or equivalent. In fact, it's quite a good idea to route your blow-off into a catch can and from there into the air box, the idea being that the fumes are re-breathed into the engine, but the heavier moisture and oil drop out into the catch can. You shouldn't need a PCV valve unless your engine is very tired and smokey.

You do not say how long it has been since your air box was clean - maybe you don't know? But why not just clean it and leave it be?
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PostPost by: Pistacchio sprint 72 » Tue Jul 23, 2013 5:53 pm

I have an oil catch tank on my super seven. It allows me to be aware when my piston rings are beginning to fail...
Yep, when you rev your engine, the cranckcase pressure increase and.... Suddenly you retreive one liter of oil in the catch tank

Well, then you have to empty it...

I think the burton elbow might do the trick but you need to continue it with some sort of tubing till the bottom of the car... Otherwise it will spill oil everywhere!

I don ?t want to cloak my carbs and foul my plugs with oil.

Hey polar bears? Sue me...
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PostPost by: billwill » Tue Jul 23, 2013 6:11 pm

In fact, it's quite a good idea to route your blow-off into a catch can and from there into the air box, the idea being that the fumes are re-breathed into the engine, but the heavier moisture and oil drop out into the catch can. You shouldn't need a PCV valve unless your engine is very tired and smokey.



Not a lot of people realise that the whole of the rear right side of the twin-cam head IS a 'catch-can'

That vent with the grommet goes into a separate chamber. Most of the oil fumes condense in there and run down that conical rubber tube back into the sump. Only the excess fumes come out of the side hole shown above and thence into the airbox or down onto the road or whatever new catcher you provide.
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PostPost by: Fred Talmadge » Tue Jul 23, 2013 6:53 pm

Just in case you don't know, you can not drive any car on a race track that vents oil to the surface. I don't know how those old timers with open oil systems do it.
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PostPost by: Pistacchio sprint 72 » Tue Jul 23, 2013 7:31 pm

Originally that is why i installed an oil catch tank in the 7 but i am not found of track days, i prefer mountains roads...
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PostPost by: frearther » Tue Jul 23, 2013 7:33 pm

I went the copper plumbing route, and it seems to work fine. 1/2-inch U.S. size copper pipe works fine. I attached the plumbing to the engine at the inner end and to the air box via heater hose at the outer end. There is a plug in the line to prevent fumes from reaching the air box.
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PostPost by: elanner » Tue Jul 23, 2013 9:02 pm

I also made a copper T piece that fits between the head and the airbox, blind at the airbox end. The leg of the T connects to a rubber tube that runs down to a narrow plastic bottle that fits in the body/chassis void behind the coil.

An oily mess under the airbox always bugged me with my old Elans, and the engines didn't seem to appreciate #4 getting fouled up, hot and bothered in traffic jams.

Other comments in the forum suggest that changing the head grommet to use a road tube might be difficult if it's old and brittle - with a risk of it breaking and bits falling into the block. Anyway, it seems to me that a road tube will oil the underbody and chassis in equal proportion to the road....

Cliveyboy's T piece looks like a nice professional solution, but I'd made my own before discovering it:
http://www.cliveyboy.com/product/lotus- ... tee-piece/

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PostPost by: billwill » Tue Jul 23, 2013 10:25 pm

Other comments in the forum suggest that changing the head grommet to use a road tube might be difficult if it's old and brittle - with a risk of it breaking and bits falling into the block.


Yes getting the old grommet out can be difficult.
Best done with a Stanley Knife with a straight blade and also a hook blade (as used for cutting Lino. and pointy nose pliers.

Cut a 15 to 30 degree chunk (cake slice) out of the grommet at the bottom, use the hook blade to cut the rubber inside and the straight blade for the hole itself and the outer bit. Use the pointy pliers to pull out that little section. Then use the pliers to squeeze the grommet so that the 15 degree gap closes up. It should then have a small enough diameter so that you can hook it out with a piece of stiff wire. (old wire coat-hanger type)
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PostPost by: Pistacchio sprint 72 » Wed Jul 24, 2013 5:51 am

You re right! An oily mess UnDER the air box .... Exactly!

Hate that!

Oil meant to be either in the engine or dripping on the floor ...not in my engine bay
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PostPost by: frearther » Wed Jul 24, 2013 11:59 am

Pistacchio sprint 72 wrote:You re right! An oily mess UnDER the air box .... Exactly!

Hate that!

Oil meant to be either in the engine or dripping on the floor ...not in my engine bay


Well said!
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PostPost by: vernon.taylor » Thu Jul 25, 2013 5:03 pm

Salut

Pistacchio sprint 72 wrote:Is one item on this list could be useful for my purpose???

I don't even recognize the parts!

http://www.burtonpower.com/catalogsearc ... m+breather


What's the 'Breather extension adaptor: Lotus Twin Cam' ?

@+

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PostPost by: billwill » Thu Jul 25, 2013 5:18 pm

vernon.taylor wrote:Salut

Pistacchio sprint 72 wrote:Is one item on this list could be useful for my purpose???

I don't even recognize the parts!

http://www.burtonpower.com/catalogsearc ... m+breather


What's the 'Breather extension adaptor: Lotus Twin Cam' ?

@+

Vernon


Image

Don't know, I regret, but I do know that I had to narrow down my piece of 15mm copper plumbing pipe to fit into the grommet in the head, so it looks as if this would do that. On the other hand it might be for some types of airbox hole. Mine has a short pipe welded on the airbox so would not need anything like that. A piece of rubber or plastic hose is used in my case to connect air box to my old vent pipe, or to hold my experimental blanked off T-piece in place.
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