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View Full Version : TR4/4A TR4A No PVC Valve OK?



KVH
02-15-2010, 09:30 AM
How can there be no PVC valve?

https://www.imageno.com/thumbs/20100215/asquoram9dpd.jpg (https://www.imageno.com/asquoram9dpdpic.html)

PeterK
02-15-2010, 09:35 AM
Probably running a road draft tube but should be a breather on the valve cover instead of a close cap.

sail
02-15-2010, 09:51 AM
I just added a breather pipe (#48 in Moss external engine) to my 4A and also am putting a breather filter on the valve cover where the PCV valve was. Changing the cap to a breather type is also an option. The difference between the 3 & 4 as opposed to a 4A which had a closed system.

Geo Hahn
02-15-2010, 01:15 PM
...The difference between the 3 & 4 as opposed to a 4A which had a closed system.

Actually it would be 3 and early 4 -- later 4s went to a simpler (than the 4A) closed system. A little too simple and a little too closed I think.

Looking squinty-eyed at the photo I think I see a tube for a breather on the side of the valve cover, just no tube connected to it (would be messy, maybe they removed it for the photo?)

karls59tr
02-15-2010, 01:46 PM
I forgot why people change over to the breather tube system on the 4A? PCV too restrictive? Does the engine run rougher with the PCV?

TR4nut
02-15-2010, 01:57 PM
[-- later 4s went to a simpler (than the 4A) closed system. A little too simple and a little too closed I think.



I agree with that one - I've considered adding the road draft tube, as I think most of my rear main leakage is because that simple system does not keep the pressure down enough.

TR3driver
02-15-2010, 01:59 PM
Looking squinty-eyed at the photo I think I see a tube for a breather on the side of the valve cover, just no tube connected to it (would be messy, maybe they removed it for the photo?) If you click on the photo, it opens larger in a new window, no need to squint <<GRAEMLIN_URL>>/grin.gif

Looks to me like they just left the port on the rocker cover open, and plugged the intake manifold port. Which would work, probably better than the late TR4 setup (which just had the port brought to the face of the air filters), since the shorter tube would offer less restriction.

TR3driver
02-15-2010, 02:01 PM
I agree with that one - I've considered adding the road draft tube, as I think most of my rear main leakage is because that simple system does not keep the pressure down enough. I agree, but not because it's too simple. Rather the passages just aren't big enough. If you had a vent line the size of the old road draft tube, it would work much better.

RJS
02-15-2010, 03:15 PM
I have experienced issues where the stock PCV cannot keep up and process the volume of blow-by on my TR4A. This particular car also has the vented oil filler cap. It resulted in crankcase pressurization and oil leaks.

I now run an open hose off the valve cover to vent the crankcase and closed the port on the intake manifold. It performs great - I barely get a drop of oil from the timing chain cover after an hour of driving (and nothing from the rear crank seal). But, I would still like to see the system perform as designed.

Next step will be a leak down test just to confirm I have no issues there. If that goes well, then I am considering modifying the PCV valve by drilling out the orifice in the body and replacing the internal spring with a stronger one. This should allow the PCV to process a larger volume of gasses under slightly more vacuum.

I'd be curious if anyone else has ever run an original but modified PCV or substituted a universal replacement.

Bob
PS: No doubt, this PCV system was of a poor design from the start. I have researched it thoroughly and found no less than 8 Leyland-Triumph technical service bulletins on this very topic spanning from Jan 1965 to mid 1966. They were obviously struggling to get it right.

TR3driver
02-15-2010, 04:29 PM
This should allow the PCV to process a larger volume of gasses under slightly more vacuum.
Except, of course, under the one condition where blow-by is maximum.

martx-5
02-15-2010, 06:00 PM
I was going to put a PCV system on my TR3, and had looked at several. The fifth version that this guy did on his GT6 (https://www.teglerizer.com/triumphstuff/emissions/emissions_67t_filter.htm) looked very promising. However, since the restoration, my oil consumption and leakage is practically zero, I'll keep the road draft tube on there. :cheers:

DanB
02-15-2010, 06:13 PM
I did something a little different. Using an in-line air filter from Harbor Freight (for airlines) I placed it where the PVC should go. It serves as a "catch can" to keep any oil from being sucked into the intake. Since I put that on there, it really has helped the leakage, and there are only a couple of drops of oil in the filter. It is clear, so you can see how much oil has been collected there. Ricers use something similar.

Dan B.

bob67bgt
02-15-2010, 06:57 PM
You are looking at my old tr4a on ebay. The engine plug on the side was removed and a original early tr4 draft tube was installed. I thought I had a hose off the valve cover but maybe not. There was not a problem with blowby messing up the engine bay. Bob

TR4nut
02-15-2010, 07:21 PM
You are looking at my old tr4a on ebay. The engine plug on the side was removed and a original early tr4 draft tube was installed. I thought I had a hose off the valve cover but maybe not. There was not a problem with blowby messing up the engine bay. Bob

I knew I saw that car somewhere before! Sweet car, and commanding a great ebay price so far. Now I'm even more sorry you didn't pick up that TR250, you would have done a beautiful job with it I think.

HerronScott
02-15-2010, 07:47 PM
With my original TR4A the prior owner had already removed the PCV setup and replaced the valve cover with a TR4 valve cover and oil filler cap. I just completed the job by installing the road draft tube.

My second TR4A still has the original setup but I don't have any experience with it yet since I haven't done anything with that one besides getting it started after it had sat 5 years in a field (smoked a little but seemed to run fine otherwise).

Scott