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TR4A - PCV - yes or no?


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Having put a search  on the Forum  'TR4A PCV valve' and not found any information, I will ask the question.

Is the PCV fitted to the TR4A worth refurbishing/refitting, or is the previous TR4 method of piping the fumes into the carb intakes, or a pipe from rocker box cover to catch tank better?

My preference would be to re-use the PCV as original. As it was still fitted to my project car, although not used since 1983, I assume it was fitted and used successfully during the 94000 miles undertaken by the car between 1965 and then?

Replacement hoses/diaphram are available from Moss, but not the small spring which would appear to be part of the body. Is this replaceable?

The engine has been completely stripped and rebuilt and should not produce excessive crankcase pressure. The car will only be used for road use.

Advice please.

Rich

 

 

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Rich,

the problem is that the Forum's search facility does not find three letter words such as PCV.  Try an external google search instead by typing the following criteria into their search page

site:https://www.tr-register.co.uk/forums/index.php?/forum/5-tr44a-forum/  TR4A PCV 

That google search of the TR4/4a forum gets lots of finds containing TR4A and PCV that should answer your question.  You could also try another search on the Technical forum in case people have posted there..

Paul

PS. I have the original PCV valve on my 4A and it seems to work fine.

And you can try the above search with TR4 instead of 4A and get more finds,

 

Edited by PaulAnderson
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Rich,

I did a lot of research on this but from a slightly different perspective because my US import project didn't have one fitted. Opinion seems to be split between experienced TR owners, if you have one and it works ok, leave it alone. If you don't or it isn't working, don't bother, vent to atmosphere with a pipe leading down to the chassis. There seems to be a view that the PCV was a bit of a gesture to US emission regs at the time, but that it isn't a particularly effective device...

Rgds

David

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Thanks all, I think I will refurb and fit and see how it goes. Just watched a video on Youtube of a TR4A running with a PCV but it was very noisy. Probably as it had a modified cover with a large hole in the middle. Sounded like a very noisy tappet!

Is there a noise with the proper original cap fitted?

Rich 

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I don’t have a PCV on my TR4A (the PO fitted the block breather pipe from a TR4), but I always wondered how important the bespoke TR4A oil filler cap was to the correct functioning of the PCV system.

Jim

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After fitting Webers to my 4A I tried using the PCV but the Webers didn't like it so I switched to a catch tank with just a tube taken from the rocker cover, after seeing the slightly acidic watery/oily gunk(about 500mls per 1000miles) that accumulated in the tank I decided that the engine was much happier without this stuff being chucked down its throat.

Cheers Rob

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On 7/18/2020 at 1:44 PM, rvwp said:

Thanks all, I think I will refurb and fit and see how it goes. Just watched a video on Youtube of a TR4A running with a PCV but it was very noisy. Probably as it had a modified cover with a large hole in the middle. Sounded like a very noisy tappet!

Is there a noise with the proper original cap fitted?

Rich 

Hi Rich,

you found my video on youtube and this is with a modified cover to show how it works.

With the correct cover with the original small drill it makes no noice at all.

I wrote this in the titel which is with the video on youtube, have you not seen this?

 

When I was a newbie I've been told the usual bad stories about this valve, but after a very close look I sadly had to realize:

a lot of TR4A driver do not understand at all how it works and what it is very usefull to!

 

The "Positiv Crankcase Ventilation" valve better shoud be called "Activ Crankcase Ventilation" valve.

It connects the crankcase and valve cover with the inlet manifold and reduces the low pressure (while driving) / vacuum (while ideling)

of the inlet manifold to a constant low pressure vaccum, it's about negativ 6 cm water column (if I remember correctly).

 

On my video you see how it suck the slack oilcap and holds it in position anyway ít is not locked!

I use it not with the vented oil cap, so it suck the air by all standard leaks where you loose oil.

 

Always there is criticism about the fact there is always oil in it!

Yes, this is true, and this is the case because it is an oil separator - and this is a problem if folks fix it "backwards", like on the photo (NOT on my TR).

Then the oil lows over the rim through the valve to the inlet manifold, that's of course not so good.

 

Sorry, photo deleted because of limited memory capacity

 

You have to fix it slightly forwards to let the seperated oil flow back to the valve cover, that works lovely!

(Sorry, no photo this evening)

After I did that I never found any oil in the hose which goes from the valve to the inlet manifold.

And it hepled me to trop the consume and loss of oil a lot. YES, install it, but please install it correctly.

Please do not use a catch tank and please do not guide the fumes to the envirement and please only believe half of the stories you have been told.

You better have a close look on your own and make your own thoughts.

Ciao, Marco

 

Edited by Z320
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Hi Rich,

here are some photos I promissed you by PM.

Safe them if you want, I have to delete them because the memory space here on the forum is limited.

My PCV valve is only a replica, the spring holding the cover was very weak, so I use a modyfied one from my grandmas "Weck" compote jars.

 

Sorry, photo deleted because of limited memory capacity

 

Inside is the diaphram (keep the upside free from oil as the workshop maual tells, it must not glue on the cover),

a "steel washer" with a coned bolt, this regulates the flow through the orifice.

The low pressure in the engine is determined by the diameter of the "steel washer", the diaphragm and the spring load.

You see I have no oil sump in there, it all flows "back" (forward) to the valvecover.

 

Sorry, photo deleted because of limited memory capacity

 

If the spring is missing, I would use a part of a SU carb spring, this does not fit exactly but could work.

 

Sorry, photo deleted because of limited memory capacity

 

Spring diameter is inside 20 mm, 22 mm high, wire is 1 mm in diameter, load before fully compressed is about 420 gramms.

Not shure this is correct - as told above my PCV is only a replica.

 

 

Sorry, photo deleted because of limited memory capacity

 

Here some old photos from my replica PCV,

the center piece with the orifice was not fixed and not sealed to the valve body, I did that with bolts and glue and had to make a rim.

 

Sorry, photos deleted because of limited memory capacity

 

Below the center piece is another spring loaded valve, this is a "not return valve" and also this way a flame trap.

You can press the valve down but cannot see what it does.

 

Sorry, photo deleted because of limited memory capacity

 

This is how I examined the amount of vacuum in the inlet mayfold and low pressure under the valve cover.

 

Sorry, photos deleted because of limited memory capacity

 

By the way, if anyone wants to get rid of his original PCV I'm interested to get it as a present.

Please don't hesitate to contact me by PM

Ciao, Marco

Edited by Z320
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Thanks Marco, very informative. As I said by Pm I now have the spring. As it's an original Smiths PCV I shall fit it as described with new diaphram  and hoses.

Rich 

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Just one other thing. Marco mentioned the importance of the engine oil filler cap. The TR4A cap is different from the TR4 cap as its a closed circuit system.

The TR4A cap is NCA from Moss.  Nor sure if any of the other suppliers can provide it.

How can I be sure that the TR4A cap that came with the engine I have is for the open circuit system? What is it's redeeming feature?

Thanks 

Rich

 

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Hi Rich, there have been many posts on the forum regarding the PCV, the majority in favour of removal. Mine went in the bin over 15 years ago and the engine breathes well using a straight pipe off the rocker cover and a TR4 Snorkel in the Crankcase below the fuel pump. 

The main reason not to fit the PCV is it improves nothing but adds about half a dozen extra parts to the engine of which the failure of any one of these parts could lead to a breakdown.  Reliability is king. 

Chris

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I use the original SMITHS PCV on both my Webered '250s. This version differs from that of the 4A in that it needs supplemental filtered air which it gets through a "T" and hose to a pipe on the air cleaner with a 1/8" orifice. I reckon the 4A version gets its supplemental air from the vented cap shown in Z320's pic above. I fashioned a copper tubing route to the back of a K&N filter housing to mimic the factory setup for mine.

My motive 24 years ago when I concocted my first Weber application with it had to do with getting stunk up with blowby fumes while diddling with idle settings under the bonnet - they have a way of defiling clothing with a vengeance.  I've done over 140K blissful miles since, replacing the first diaphragm a few months ago. 

 

Tom

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Thanks Marco, neither of my inlet manifolds are that shape - they both have an angled boss, one has what looks like a vacuum gauge connection tapped into it.

No problem for me if you need to delete the photos.

Pete

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On 7/18/2020 at 10:44 PM, Z320 said:

Hi Rich,

you found my video on youtube and this is with a modified cover to show how it works.

With the correct cover with the original small drill it makes no noice at all.

I wrote this in the titel which is with the video on youtube, have you not seen this?

 

When I was a newbie I've been told the usual bad stories about this valve, but after a very close look I sadly had to realize:

a lot of TR4A driver do not understand at all how it works and what it is very usefull to!

 

The "Positiv Crankcase Ventilation" valve better shoud be called "Activ Crankcase Ventilation" valve.

It connects the crankcase and valve cover with the inlet manifold and reduces the low pressure (while driving) / vacuum (while ideling)

of the inlet manifold to a constant low pressure vaccum, it's about negativ 6 cm water column (if I remember correctly).

 

On my video you see how it suck the slack oilcap and holds it in position anyway ít is not locked!

I use it not with the vented oil cap, so it suck the air by all standard leaks where you loose oil.

 

Always there is criticism about the fact there is always oil in it!

Yes, this is true, and this is the case because it is an oil separator - and this is a problem if folks fix it "backwards", like on the photo (NOT on my TR).

Then the oil lows over the rim through the valve to the inlet manifold, that's of course not so good.

P1150648-b.JPG.37fffaee5dc058916f6338bce758cfda.JPG

You have to fix it slightly forwards to let the seperated oil flow back to the valve cover, that works lovely!

(Sorry, no photo this evening)

After I did that I never found any oil in the hose which goes from the valve to the inlet manifold.

And it hepled me to trop the consume and loss of oil a lot. YES, install it, but please install it correctly.

Please do not use a catch tank and please do not guide the fumes to the envirement and please only believe half of the stories you have been told.

You better have a close look on your own and make your own thoughts.

Ciao, Marco

 

 

On 7/19/2020 at 10:30 AM, Z320 said:

Hi Rich,

here are some photos I promissed you by PM.

Safe them if you want, I have to delete them because the memory space here on the forum is limited.

My PCV valve is only a replica, the spring holding the cover was very weak, so I use a modyfied one from my grandmas "Weck" compote jars.

P1160933-b.JPG.4c139da861ed29940a1ee6f473433533.JPG

Inside is the diaphram (keep the upside free from oil as the workshop maual tells, it must not glue on the cover),

a "steel washer" with a coned bolt, this regulates the flow through the orifice.

The low pressure in the engine is determined by the diameter of the "steel washer", the diaphragm and the spring load.

You see I have no oil sump in there, it all flows "back" (forward) to the valvecover.

P1160935-b.JPG.52ced901f9d9e1b2c2f9efd51856ef88.JPG

If the spring is missing, I would use a part of a SU carb spring, this does not fit exactly but could work.

P1160937-b.JPG.4d450ebab6de527a250ebb7440182a0a.JPG

Spring diameter is inside 20 mm, 22 mm high, wire is 1 mm in diameter, load before fully compressed is about 420 gramms.

Not shure this is correct - as told above my PCV is only a replica.

P1160941-b.JPG.609b6ea5ef795a92f1afef7b1028fd20.JPG

Here some old photos from my replica PCV,

the center piece with the orifice was not fixed and not sealed to the valve body, I did that with bolts and glue and had to make a rim.

P1260102-b.JPG.76b3e8f44c61e5b3ce34cfdf9571d74d.JPG

P1260137-b.JPG.34464d3080b8b547b3fac95dfcdef02b.JPG

Below the center piece is another spring loaded valve, this is a "not return valve" and also this way a flame trap.

You can press the valve down but cannot see what it does.

P1260123-b.JPG.7893f00c4081e2d8763c7ae5c1604d8f.JPG

This is how I examined the amount of vacuum in the inlet mayfold and low pressure under the valve cover.

P1270422-b.JPG.5bf0b811fcf581b98eb18a7c6359d1f0.JPG

P1270606-b.JPG.83e96e2ceffdc7157c4eb4523c34f71a.JPG

By the way, if anyone wants to get rid of his original PCV I'm interested to get it as a present.

Please don't hesitate to contact me by PM

Ciao, Marco

Just thought I'd reply quoting this post and then the photos might stay for the benefit of others even if they are deleted by Marco.

Paul

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3 minutes ago, PaulAnderson said:

 

Just thought I'd reply quoting this post and then the photos might stay for the benefit of others even if they are deleted by Marco.

Paul

I think you`ll find they will disappear as well.

Stuart.

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