Crankcase breather S130 twink

[JonB]

I found the breather tube!

[vincereynard]

That's a start!

It's probably worth getting a new grommet (No 13) for the head whilst you are at it.
Mine was rock hard.

[JonB]

New gasket first (no. 2)!

[MarkDa]

I've just realised that I've never had one of those!
It's always sealed up well enough as far as I could tell.
Will investigate getting one.

[vincereynard]

I've not bothered.

Fillet of silicone on the air box metal.
Allow to flash off
Grease on the fibreglass cover
Press gently together.

It "should" make bespoke seal with your raggedy cover.

[MarkDa]

I love the built in instructions on case one needs reminding in more senior moments!

[billwill]

If you take a look at pictures of the FORD engine 105E from which we use the block you will see that the large hole above the fuel pump is the crankcase breather hole for those engines. And is fitted with a tin can type oil mist collector.


When the Twin Cam head was designed they decided to use that hole as a drain for oil mist from the head so they designed a corresponding hole in the head and found/commissioned the curiously shaped conical rubber drain tube.

Mean while breathing is still needed, so a nearly rectangular box is moulded onto the head (omitted in very early twin-cam heads) for oil mist to settle and a hole in the side (which is at the back right-hand (inlet) side of the head) is the actual pressure equalization breather. In the early cars this was a simple tube draining down onto the road near the bell housing, but this was non-ecological so it was changed to a tube to the air box, so that the oil mist would eventually be sucked into the engine and burned.

Moulding a hollow mist settling box as part of the head, of course, requires a 'core' in the hollow while the hot metal is poured this filler is made of sand and lightweight glue so that it can be broken up and removed after the metal has cooled. Support for the 'core' in the sand mould is done with two thick stems of glued sand, these cause the two holes on the underside of the head casting, visible in the photo below. The front one is used as the afore-mentioned hole for the conical rubber tube and the second, rear-most hole, is closed with a core-plug (aka Welch plug).

I presume this is why a conical rubber tube is needed, if they had made that upper hole the same size as the crankcase hole, perhaps the oil-mist box core support (it's only sand and glue) would have been too weak, resulting in too many failed head castings.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Revised to correct the location of the breather hole in the block.

[nmauduit]

If you take a look at pictures of the FORD engine 105E from which we use the block you will see that the large hole above the oil pump is the crankcase breather hole for those engines.

is it not above the fuel pump rather than oil pump?

actually I am considering reverting that block hole to its original crankcase ventilation purpose on my car, to avoid a conspicuous modification that cam cover drilling would do, yet allow additional venting... I was originally thinking of plugging the head mist chamber from above only, and use a plugged elbow such as

block breather elbow

[webbslinger]

A 1/4" wire- wound socket flex drive is THE ticket for easily getting at the bottom carb nuts.

[billwill]

is it not above the fuel pump rather than oil pump?

Ooops, yes.

[Chancer]

actually I am considering reverting that block hole to its original crankcase ventilation purpose on my car, to avoid a conspicuous modification that cam cover drilling would do, yet allow additional venting... I was originally thinking of plugging the head mist chamber from above only, and use a plugged elbow such as

FP280A_Breather_Elbow.jpg

At anything above medium/high engine revs loads of o?l will be thrown out of that orifice, no way would you want that in the inlet tract, the stock breather used a PCV valve allowing venting only under high vacuum conditions.

On my race X/flows I would block that breather hole and vent from the rocker cover.

[nmauduit]

At anything above medium/high engine revs loads of o?l will be thrown out of that orifice, no way would you want that in the inlet tract, the stock breather used a PCV valve allowing venting only under high vacuum conditions.

On my race X/flows I would block that breather hole and vent from the rocker cover.

yes, but precisely drilling the cover is what I'd like to avoid... plus the blow back is coming from the bottom : when venting only from the top some people say it may contribute to accumulate oil above. I'm not going to vent in the air box of course - neither from the back head regular vent which I'll keep - but to a catch tank/can. I've seen some fuel pump blanking plates that are meant to reduce the oil spill up the elbow, I may consider that as well :

next year will tell.

[Chancer]

Recognising the problem and being on a mission to solve it you will probably succeed, from my experience the stock breather can without a PCV valve does nothing to stop the o?l loss.

There was never any mayonnaise in my catch tank and the o?l expelled was as clean as the engine o?l which I changed regularly, I was however obsessive about piston bore clearance and running in, in the end I fitted used an inverted laboratory flask with a brass drain coCk fitted in the cap (now at the bottom) the breather pipe entering through a close fitting grommet at the top. When it was getting full I would remove it, open the cock and drain off the tiny bit of clean water sitting at the bottom then drain the rest straight back into the engine, a litre of Mobil 1 cost a lot back then!!!