6 replies to this topic

[sliw1971]

I'm working on my first mini project and currently rebuilding the engine (early 1275 A+).  I have bought a set of 1 1/4 twin SU's, but there is nowhere on these carbs to fit the breather pipes from the clutch and timing covers.  Firstly, will the carbs without the breather inlet be compatible with the engine and if so, where do I route the breather pipes.

 

Thanks

[nicklouse]

Most inlets manifold have a boss for this. Drill tap and fit a union.

[Wim Fournier]

But be carefull with using the inletmanifold as source for the crankcase ventilation. You need a positive cranckase ventilation valve. Because, when you take your from the acellerator the vacuüm in the inzet manifold gets very deep, much to deep for the drankcase vantilation. So, it should be shut up as long as you don't put your foot down. The halve consists of a membrane that is hold up by a spiral  spring and there is a venturi in the inluisde of the halve house to restrict the airflow from the crankcase. The instrument has the form of a mushroom.

[Stevie W]

Hi,

I have twin 11/4" SU's on the log type manifold and there is a drilling in the manifold mid way betweenthe carb ports.

The Cooper "S" set-up uses a PCV (positive crankcase ventilation) valve, which also used to be known as a "gulp" valve. This valve type allows crankcase ventilation during normal use, but if there's a backfire through the inlet, the sudden pressure rise closes a diaphragm and prevents the backfire entering the crankcase.
I've plumbed the timing chain and clutch housing breather into this valve and used a plastic "Y" piece to join the two hoses from the breathers into one hose that connects to the PCV.

Hope this helps,

Cheers, Steve.

Edited by Stevie W, 11 October 2015 - 06:01 PM.

[sliw1971]

Thank you all for your responses.

 

I have searched the mainstream mini parts suppliers online, but cannot find a PCV valve for minis.  Would you know where I could obtain a mini PCV valve or will any type of PCV valve do.

 

I have also read other threads on the forum making reference to catch tanks.  Is this a viable alternative to connecting into the inlet manifold?

 

Thanks once again

[Stevie W]

Hi,

 

Minispares list the original PCV valve, part No 13H5191, but look to be out of stock at the mo!!

[Spider]

One like this will do the job fine

 

http://www.mx5parts....1-25-p-783.html

 

While that one is designed to fit in to a grommet on the rocker cover, it will work equally well if shoved in to a hose, or look around for one that does fit inline. Be sure to use proper emission type hose, heater hose and stuff like that isn't any good for this application.

 

I'd also suggest buying a new one as they do gum up and some can't be cleaned.

 

<Edit: Here's possibly an easier one to fit

 

http://www.bskspeedw.../pcv-valve.html

 

IMO, all the BMC / Leyland / Rover designed ones were not remotely special >

Edited by Moke Spider, 18 October 2015 - 07:44 PM.