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I beg to disagree with the last bit, the "venturi effect", while agreeing strongly with the upsloping hose from block to tank.

Flow below the engine bay is extremely turbulent, so any venturi effect will be transient and minimal.

I've posted a pic of my setup before so I won't again.     Catch tank on bulkhead, small K&N filter on T, between rocker and tank, seperate upsloping hose from block.   Small visible steam effluent from filter on cold days, NO oil in the tank, ever!

John

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Hi guys. Right now I am simply venting straight out. Letting mother nature take care of everything. Engines happy enough. The cranks venting happily out the old manual fuel pump. No pressure now. 

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3 hours ago, john.r.davies said:

image.png.29ecd4d2e46b42a84dd5dbdf2cd36b28.png

Tom, please expalin your layout?

Looks to me as if you have a T-connector that links together the rocker cover vent, AND the rear air filter housing to the PCV, which is mounted on the centre Weber intake manifold, which will suck in rocker cover gas and air from the filter.    Since the filter will flow vastly more air than the crankcase, I would expect far more of that tahn gas, and since Weber manifolds are not linked by pressure balance tubes, your Nos.3 & 4 bores wil be getting a lot more air than the others.   Have you compensated for that in way you have set the middle Weber?

Further, a second hose appears from behind the rear of the block, and disappears under the PCV.  Is this the vacuum control for the Dizzy?   If so, I would fear fluctation in the vacuum not strictly to do with throttle opening, as the PCV open and closes so near to the take off to the dizzy hose.    Clearly, you are not concerned by this fear!

John

Sure! The T-connector is original to the TR250 and goes to a 1/8" orifice in the air filter housing, as it does on the factory setup. The SMITHS PCV valve balances itself to ensure a slight vacuum on the crankcase via the valve cover nipple, again as per original. The CANNON Weber manifold does in fact have balance tubes which are seen in the photo, so that all tracts are fed the lovely lubricated gases equally ( TWM manifolds are different ). The 2nd hose goes to the brake servo, not the distributor. 

Z320 is sadly mistaken; this system works flawlessly. The engine uses 1 US quart of oil in 3000-4000 miles depending on driving style despite 134,000 miles on the rings. The head has 97,000 miles, no valve guide seals ( bronze guides ) and the rocker shaft has an auxiliary oiler. 

I know, much of this flies in the face of conventional " wisdom " but it is nothing more, nor less than an humble attempt to duplicate the PCV system original to the car. Even the (3) hoses on the tee are the original TR250 fitment ( NLA ). 

The same system is employed on my concours TR250 as well. 

 

Tom

TR PICTURES 003.jpg

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19 minutes ago, Z320 said:

Hi Tom,

the vertical connector of your PCV valve is (not visible) connected to the vacuum of the inlet manifold?

And not to the hose going backwards in the direction to the bulkhead?

Ciao, Marco

Hi Marco,

Both the PCV valve and the servo hose are connected to the inlet manifold. The valve cover sees a reduced vacuum due to the PCV valve mechanism.

Detail pic below.

 

Ciao,

Tom

TR PCV AND SILENCER SHOTS 016.jpg

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2 hours ago, murrayarnold said:

Hi guys. Right now I am simply venting straight out. Letting mother nature take care of everything. Engines happy enough. The cranks venting happily out the old manual fuel pump. No pressure now. 

You need to consider the point of the flame trap, also it will not stay clean very long.

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The flame trap is if the rocker cover vent recycles through the inlet system. It does that on my mgb. The triumph, as it has no filters, doesn't. The Pipe simply vents out under the car. Easy. 

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1 hour ago, murrayarnold said:

The flame trap is if the rocker cover vent recycles through the inlet system. It does that on my mgb. The triumph, as it has no filters, doesn't. The Pipe simply vents out under the car. Easy. 

Your car you know best?

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Its a fact. No cycling of gasses, no flame trap requirement. The breather tank is really just a nice add in feature if you maybe live in North America and have smog controls etc. Or if your an enviromentalist. I have no need for either. So I've got the crank breather sorted. Thread closed. Thanks for everyone's help. Job done. 

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Hi Tom,

thank you very much for your photo, this exlpain very much - but not all.

From your post I realize you know how the PVC valve works:

it reduces the low pressure - but often vacuum - of the inlet manifold to a slightly low pressure

(I meassured this some years ago with about 40 - 60 mm water column, zero with engine off on the photo)

to suck the vapours "activ" out of the valve cover / engine / cankcase.

P1270606-b.thumb.JPG.3e61083676ef21aaefb482938a12f72c.JPG

You will know why you also connect the PVC valve with the T-shape to the air filter and suck out air there too - as a bypass to the carbs.

You shure have reasons for this, I would not do this because I see no benefit.

But luckily this engines are tractor engines and you can level this by a different carb setting and the connecting tube of the inlet manifold.

 

The PVC valve is made of metal - this why it is "cold". And because of this reason it is also a oil separator.

When you lift the cover off you always find oil in there, I've never seen a dry one.

No problem, original the oil flows back to the valve cover ("oil recyling") if the PVC valve and the hoses are installed correct.

Forward on a TR4A, backwards in your case, but automaticly correct on your setting because the hole engine is installed backwards.

P1150648-b.JPG.9e4520dcf67c6c4dafaadaa2b60ec774.JPG

From your last photo the flow back of the oil to the engine may work, but I'm not shure.

From your first photo and shure from the red TR I expect the oil will flow to the carb's air filter.

If I'm wrong please sorry me, I wish you always a safe and pleasent drive.

Ciao, Marco

 

edit:

low pressure 40-60 mm water column is with my replica PVC

and with a not vented oil filler cap (original on the 4A is a vented oil filler cap).

Original setting may give different results.

Edited by Z320
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On 10/21/2020 at 6:11 PM, Z320 said:

Hi Tom,

thank you very much for your photo, this exlpain very much - but not all.

From your post I realize you know how the PVC valve works:

it reduces the low pressure - but often vacuum - of the inlet manifold to a slightly low pressure

(I meassured this some years ago with about 40 - 60 mm water column, zero with engine off on the photo)

to suck the vapours "activ" out of the valve cover / engine / cankcase.

P1270606-b.thumb.JPG.3e61083676ef21aaefb482938a12f72c.JPG

You will know why you also connect the PVC valve with the T-shape to the air filter and suck out air there too - as a bypass to the carbs.

You shure have reasons for this, I would not do this because I see no benefit.

But luckily this engines are tractor engines and you can level this by a different carb setting and the connecting tube of the inlet manifold.

 

The PVC valve is made of metal - this why it is "cold". And because of this reason it is also a oil separator.

When you lift the cover off you always find oil in there, I've never seen a dry one.

No problem, original the oil flows back to the valve cover ("oil recyling") if the PVC valve and the hoses are installed correct.

Forward on a TR4A, backwards in your case, but automaticly correct on your setting because the hole engine is installed backwards.

P1150648-b.JPG.9e4520dcf67c6c4dafaadaa2b60ec774.JPG

From your last photo the flow back of the oil to the engine may work, but I'm not shure.

From your first photo and shure from the red TR I expect the oil will flow to the carb's air filter.

If I'm wrong please sorry me, I wish you always a safe and pleasent drive.

Ciao, Marco

 

edit:

low pressure 40-60 mm water column is with my replica PVC

and with a not vented oil filler cap (original on the 4A is a vented oil filler cap).

Original setting may give different results.

Hi Marco,

I believe the oil is drawn into the inlet manifold, not the crankcase. On mine, the flow into the inlet is enabled by the small amount of air from the air cleaner orifice. Also, I believe the vacuum on the valve cover is much less than that of the inlet manifold though I've never measured it. ( Did you ever measure the full inlet manifold vacuum? )  As you know, the valve constricts the opening when the inlet port is under vacuum until it reaches a balance with the pressure from the crankcase.

On the 4A my thinking is the original vented oil cap allows a little more gas flow from the crankcase into the inlet as well. Without that, I can imagine more condensed oil might accumulate in the PCV. 

Ciao,

Tom

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  • 10 months later...

coming back to this topic...

I have a tubing from the valve cover and crankcase (fuelpump) into a catchtank. After reading some more, is there any particular advice on the inside diameter of the tubings? I have a 1/2" coming from the valve cover and 3/8" coming from the crankcase. I am planning to have a 3/8" all around and since valve cover and crankcase are connected with each other thru the internal engine, I do not expect much difference.

Opinions?

Jochem

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4 hours ago, JochemsTR said:

coming back to this topic...

I have a tubing from the valve cover and crankcase (fuelpump) into a catchtank. After reading some more, is there any particular advice on the inside diameter of the tubings? I have a 1/2" coming from the valve cover and 3/8" coming from the crankcase. I am planning to have a 3/8" all around and since valve cover and crankcase are connected with each other thru the internal engine, I do not expect much difference.

Opinions?

Jochem

Always go for as big a tube as possible. so I would up the crankcase one to at least 1/2" as well

Stuart.

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