Do I need a PCV assembly or can I just vent ?

[Tom_Lynch]

Do I need a working PCV on a TR4a or can I vent into the engine bay via a filter?

 

[Darrell_Walker]

Your best bet would probably be to install a road draft tube. But I've run with just the valve cover vent open. You will probably get some oil mist out of that (at least I do, with an alloy cover that doesn't have any baffle).

There is actual benefit to having positive ventilation in the crankcase, though I'm not sure the stock system on the 4A really provides that, anyway.

 

[rlich8]

You "could" do that...but why not make it work? It's not a very complicated system, it was designed well and when functioning properly, it works nicely.

If everything is in place (hoses, PCV valve, non-vented oil cap), it shouldn't be too hard to make it work.

Remove the PCV valve. You can dis-assemble the PCV by unclipping the metal lid. Check the diaphragm for tears or a rupture. The one-way valve should only blow one way. I tested mine by pushing and pulling w/ a few pound of air from an air compressor (not too much!). At first it wasn't working.

Scrape all the gunk out of there with a pick or something, and degrease it (a repair shop should do it for free or a cup of coffee). Just get it as clean as possible. Maybe take a wire pipe cleaner and clean out each of the tubes coming off of it. To make mine look new I wire-wheeled it on a grinder. Degrease it again. I also cleaned off the spring and the small plate w/ nub.

I coated the diaphragm with a small amount of grease to renew it. Put everything back together, reinstalled it, and everything worked just fine.

I would urge you to make it work, but if you must, you can block off the valve cover vent w/ a small heater hose blocker, and you can find a proper plug for the manifold. Then, just find a TR3 valve cover cap. That would be the "proper" way to do it.

Remember that your rear main seal likes a little bit of a vacuum in the crankcase in order for it to work properly. Just something to think about.

Best of luck,
Roy

 

[Tom_Lynch]

OK - got it. Will get it working. Thanks guys.

 

[rlich8]

OK - got it. Will get it working. Thanks guys.

Anytime, Tom! That's what we're here for.

Have fun with your 4A! I know I'm having fun with mine! Past needing to reinforce my differential mounts and do all that jazz...I love this car :laugh:

 

[TR3driver]

IMO there is a fundamental problem with the factory "PCV" design on the 4A.
Blowby is greatest when the throttle is wide open. But when the throttle is wide open, there is no vacuum in the intake manifold and hence no flow through the PCV valve unless the pressure in the crankcase rises above ambient pressure. And if the pressure rises enough to blow through the PCV valve, it's also going to blow through the rear main seal.

And the design doesn't actually produce "positive ventilation". For that, you need a fresh air intake. Then at WOT, the blowby flows backwards through the fresh air intake rather than building up pressure in the crankcase.

PS, on a buddy's TR6 with blowby problems (tired rings), we just hooked the rocker arm cover tube to a long piece of heater hose and let it hang down near the road. He was very pleased with the result, as it stopped the engine from blowing oil out in all the other places. Not the best setup of course, but it worked. I would have thought it would have still let go a few drops of oil from the tube after parking the car, but he said it didn't. No doubt the heater hose would rot in a few years (from the effect of the crankcase gases on the rubber), but he was planning to rebuild the engine by then anyway.

 

[DanB]

Hey Randall,

Get your TR6 buddy to put a catch can of some sort under that tube. One of the guys in our club has a big healey with the same type setup, and he catches the oil, then puts it back in the engine. He just has an old quart gear oil bottle hanging there by the handle with the hose running into it.

Dan B

 

[Geo Hahn]

...he catches the oil, then puts it back in the engine...

Catch 22 fans will be reminded of the 'Soldier in White'.