Yeah, I know, that's why I did it that way.  I posted in case Dan wanted to do what I did.

Kevin ... excellent info and explanation! Thanks for the link.

Now that I've learned something for today, I should take the rest of the day off and play with the Mini.

I have posted this before, here is how the Smiths PCV valve works.

//www.mgaguru.com/mgtech/engine/cv103.htm 

As others have said, the vac port provided on later SUs replaced the need for this. However, the PCV valve does flow more fumes, so works better if your engine is getting long in the tooth.

"Calver wrote an article in one of the Mini mags last month which is very imformative as to where and why and how much you need to vent a Mini engine."

As I no longer have access to the magazine, could anyone scan the article and E-mail it to me?

Haha Thanks! As the Fonze used to say "I KNEW that!" (I doubt he could type any better than me!)

Then again I've had PVC - premature ventricular contraction. That's when your heart, instead of going "thump-THUMP, thump-THUMP" goes more like "thump-thump-THUMP, thunp-thump-THUMP".

Tomorrow I play with crankcase vents.

The vent on the carb works just fine. Fit all of the oil/air separators you can, drop gear, timing cover, tappet chest. If you fit a breather at the fuel pump take off it will need some separation on a street car. A line from the valve cover is a good thing, however a vented cap on the valve cover is not a priority for me, as there is always enough coming into the system.

Calver wrote an article in one of the Mini mags last month which is very imformative as to where and why and how much you need to vent a Mini engine.

Fitz there is no need for a PCV valve the way you have yours connected.

Dan that is PCV (positive crankcase ventilation).

The PCV is needed if there is intake manifold vacuum to be controlled. It has a variable orifice .

at high vacuum/closed throttle (idle or decel)  there is low air flow from carb to engine. A lot of vacuum drawing air or fumes out of the crankcase or breathers into the intake manifold would lean out the mix too much. So the PCV's internal tapered mechanism moves with high vacuum against its internal spring to nearly close the orifice and only allow a small amount of ventilation. At lower vacuum/open throttle the spring pushes the mechanism into position to uncover/enlarge more orifice , and more ventilation is allowed.

I have not followed the modern PCV story, but I know my 1981 Volvo did not have a PCV . It had both small and large ventilation hoses connected to  a common ventilation fitting set into a port on the block. The small hose was connected to downstream of the throttle, the larger hose was connected to upstream of the throttle. Gives same results as a PCV without needing a PCV itself (or clog up). However, it did have a mesh flame trap in the fitting that clogged up and with no other site of ventilation,  the crankcase pressure rose, oil went spewing out the seals .

As I understand them, they are essentially check valves.  They open from positive pressure in the crankcase to allow it to be bled off and sucked into the intake.  They close if the pressure differential is the other way, such as if you had a backfire.

FWIW, for 10 years or so, I've had my three vents running to a plastic gatorade bottle with a little filter on top.  A couple months ago I decided to see if I could make my car smell better since the gatorade bottle was just on the firewall where the windshield washer bottle was supposed to go, the fumes would enter the cabin.  I routed the three vents to a common hose and connected it to the port on my HIF44 that was meant for it.  I ended up not putting in any PCV valve but do have the vented oil filler cap.  I've put about 1600 miles on the car since I made the change and it's one of the better improvements I've done to the car.

Great info... Thanks!

A question: what does a PVC valve actually do? (All I remember is that if it doesn't rattle it needs cleaning or replacing...)

• Does it remain closed until crankcase pressure buildds up a bit (I doubt it)?
• Does it prevent backflow?
• Does it only allow the vacuum pull from the manifold to sip perodically?

You can still get diaphragms for the old Smiths one. p/no 27H7758, Aus$20 here in Oz.
The whole Smiths PCV valve is p/no $13H5191/2. Aus$120 approx here in Oz.

The Toyota style one I pictured replaces the whole Smiths valve. Works the same, as far as I can tell.
In USA I'd go to Autozone or wherever, and pick one that's common.

I am sort of doing a mongrel engine from a variety of years. Does this mean I can take the diaphragm style from the old Smiths diaphragm type and just replace it with a modern version like the Toyota style?

Can you still get diaphragms for the old type?

Terry

PS yes you can:

//www.minimania.com/part/27H7758/Gulp-Smog-Valve-Diaphram

but the gulp valve body is $74

Cooper 1275S and A/A 1275 etc which had a Smiths PCV valve, had a filler cap which had a breather `filter' in them. The hole in the cap where the air enters the rocker cover is 4mm, I measured it.
The Smiths PCV valve was used on various BMC motors including A and B series.

I run a Toyota style aftermarket one, same as this- and it works fine. Pretty much any PCV valve of a 2L or smaller motor will work.

Can you get the parts to recreate what was there back in the 60s?

From what I've read (very briefly, I admit!) the PCV valve should be calibrated to the engine. Or is that the  rationale for the 4mm hole you mention?  Any recommendations for a PCV valve that would go in-line between hoses?

Way back when I was having problems with a flooding carb, I took it to a very knowledgeable mechanic, who capped the port on the carb, telling me it was one of the problems. (The flooding problem turned out to be the inlet float valve not having enough tolerance... sorted long ago.)

With my engine tending to run rich, I think this may be my first experiment.

I would run the 2 vents you have to a PCV valve on the manifold. This sucks fumes better than the vac port on the carb.
Then fit either a vented oil filler cap, or run a hose from the rocker cover to the air filter to let air IN.
In theory this hose should be restricted with a 4mm hole (as the vented cap has) but a friend with a 1380 stroker is running a 3/8" hose there, no problem.

Why not have your Y go to the port on the carb?

This is the continuation of my quest to keep exhaust fumes out of the cabin.

• 1275 Metro high compression engine
• front and back crankcase vents complete and intact
• HIF44 on alloy intake manifold,with cone type air filter
• The carb has a crankcase port whch is curretly capped.
• the alloy intake manifold does have a vacuum port currently sealed with a set screw.
• exhaust system overhauled - see thread: Getting the stink out - exhausting
• crankcase vents are joined in with a Y-pipe and then to the back-plate of the cone filter where fumes should be drawn into air stream into carb.
• no signs of crankcase pressure build-up

My plan is to recreate a decent crankcase ventilation system that will capture and control fumes.

1. Should I connect the crankcase vent hose to the carb port?
2. If I do so, do I need a PCV valve, and where would I place it? Generic part suggestions?
3. Is the sealed port on the intake manfold of any use or is it intended for a brake booster vaccuum source? (I have unassisted disk brakes.)

Help me design a simple system.