oil blow by

[alfert]

Today i noticed a lot of oil leaking out of the air intake box. My engine is new and when I got it back from the builder, the tube from the head to the air box was missing so I used a piece of rubber tubing ( a little smaller ID) that fit the hole and connected that to the intake. After running the engine in my garage (it has not yet been on the road) I noticed a fair amount of oil under the engine. I assumed something was loose and would tighten it later. I started it a couple of more times and each time the puddle got larger.

I jacked the car up, oil all over the place. It seems to go into air box, leak out and then down on to the starter and everything else. The last time I started it , I could have sprayed mosquitoes! Now I know why. I don't know why the breather is pumping oil??? The oil pressure is not excessive and the level is not high. Can someone educate me as to what may be happening and what I should try to do??
Thanks,
Brian

[alexblack13]

Hi Brian,
It will more than likely be leaking where you have the tube inserted into the head. Obtain the correct part, which has a shoulder welded or brazed onto it onto which is fitted a rubber gasket/ thick 'O' ring. A hose fitted over this tube then connects to a stub of the same diameter on the carb' backplate. Where did your tube / connector go? Does your re-builder not have it? If not they are obtainable OK. I suggest you get one before going much further. It would also be a good idea to make sure this is where the oil is leaking from your motor. Using a rubber hose pushed tightly into the head breather 'hole' might also have reduced the hose bore size and could be restricting the engine's breathing which is not a good idea. Crankcase pressure will cause a lot of leaks. These engines leak easily as they are without giving them an even better reason to do so. Many owners fit a second breather outlet system to help reduce the crankcase pressure and in turn keep leakages to a minimum.

I have also seen a rubber elbow fitted into the head breather hole, onto which a metal breather tube was fitted and used to carry the fumes to a catch tank or fed along the chassis. The fed along the chassis option is not a good idea if using the car for track days! Helps keeps the frame in good condition though!

Hope you find it OK..

Alex B....

[alexblack13]

Having another think on this Brian, It may be that the head rear oil drain may be blocked. Possibly by the wrong head gasket fitted. Not exactly certain on this but I think the head drains down one of the bolt holes and in turn down into the sump via a drain hole. Needs the correct gasket to work though.

Anyone else comment?? As I said not positive here.

You will find it so don't panic..

Alex B....

[oldelanman]

Hi Brian,
I don't know if the breather tube is the same on Weber and Stromberg heads but on my Stromberg head the original tube is one piece steel and has a fine mesh conical filter soldered in at the head end, presumably to trap the larger droplets of oil and encourage the oil mist to condense in the head and drain back down the breather into the sump. Any replacement tube you make up should I think have this mesh filter.

That said, even without it, I would not have thought you would get the problem you describe - particularly not when the engine is just ticking over. It sound like you may have a blockage somewhere as Alex says. As your engine has just been rebuilt I would be inclined to speak to whoever did it and see what they have to say.

Good luck.
Best regards,

[Mr.Gale]

A simple test would be to start the engine, remove the oil filler cap and place the palm of your hand over the hole. You should feel a slight flutter, if it is excessive then you might have a serious problem. Rings not seated, broken ring, ring gap too wide?

Gale

[69S4]

Hi Brian,
I don't know if the breather tube is the same on Weber and Stromberg heads but on my Stromberg head the original tube is one piece steel and has a fine mesh conical filter soldered in at the head end, presumably to trap the larger droplets of oil and encourage the oil mist to condense in the head and drain back down the breather into the sump. Any replacement tube you make up should I think have this mesh filter.

When I changed my Stromberg airbox about 10yrs ago I replaced the original tube with the mesh with a plain steel one and it's made no difference to oil mist flow. The seal at the engine end isn't wonderful and you do notice a little bit of oil staining in the area but very little, certainly no liquid drops. Fumes come up the tube but even after 3000 miles last year there are no drops of oil inside the airbox, just a generalised oil dampness. I'm not sure what's causing Brian's problem but it shouldn't be pushing that amount of oil into the airbox. I'd be contacting the engine builder to start with.

[types26/36]

I could be totally wrong here but isn't the gauze fitted in the tube a "flame trap" to prevent a flash back from the carbs and nothing to do with oil mist

[oldelanman]

I could be totally wrong here but isn't the gauze fitted in the tube a "flame trap" to prevent a flash back from the carbs and nothing to do with oil mist

Brian, that does sound like a more plausible explanation than mine.

When I changed my Stromberg airbox about 10yrs ago I replaced the original tube with the mesh with a plain steel one and it's made no difference to oil mist flow. The seal at the engine end isn't wonderful and you do notice a little bit of oil staining in the area but very little, certainly no liquid drops. Fumes come up the tube but even after 3000 miles last year there are no drops of oil inside the airbox, just a generalised oil dampness. I'm not sure what's causing Brian's problem but it shouldn't be pushing that amount of oil into the airbox. I'd be contacting the engine builder to start with.

Stuart, I too replaced my original tube to get rid of the grommet in the head which I found went hard and let the tube rattle about. I used 15mm copper tube and tapped the head to take a compression fitting - the hole is just right for a 1/2" BSP tap. I did fit a gauze mesh in the new tube though.

[oldelanman]

http://cgi.ebay.co.uk/Lotus-Twincam-Breather-Pipe-Airbox-head-Weber-Dellorto_W0QQitemZ120546624955QQcmdZViewItemQQptZUK_CarsParts_Vehicles_CarParts_SM?hash=item1c112385bb

Just spotted this on ebay might be of interest to Brian....or is that your bid on it already ?

Regards,

[Alasdair]

There is no way there can be that much volume of oil at the breather location at the back of the head unless, there is way to much oil and, extreme blow by.

I would take a good look at rubber oil return from head to block, installed incorrectly or split?