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PanP
07-19-2014, 02:37 AM
Hi All,
I have been tracking down a low vacuum condition on my 1973 six. I get the most vacuum with all emissions ports plugged, including the brake booster(which was leaking). The carbs have been rebuilt, they and the motor run the abosolute best with the crankcase vent(from the valve cover)ports plugged. Doing this obviously leaves the vent tube from the valve cover open.
My questions are: 1) Would just a naked valve cover vent tube allow enough crankcase ventaltion?
2) If I just ran the vent tube to one carb should I install a inline PCV? has anyone done this?
3) Being that the motor is supposed to be leak free ie: tight valve cover filler cap, sealed oil dipstick. where does fresh air enter the crankcase from?

Right now the motor runs (dare I say) perfect. The moment I start to re-plumb the emission hoses it begins to run crappy, so I know there is leaking going on in the hoses or the motor (hence the pcv idea) At this point it is basically a motor with two carbs on it and runs best, I have no problem leaving this way just concerned about crank ventilation.
Thanks for any help

Brain

TR3driver
07-19-2014, 03:42 AM
Hi All,
I have been tracking down a low vacuum condition on my 1973 six. I get the most vacuum with all emissions ports plugged, including the brake booster(which was leaking). The carbs have been rebuilt, they and the motor run the abosolute best with the crankcase vent(from the valve cover)ports plugged. Doing this obviously leaves the vent tube from the valve cover open.
My questions are: 1) Would just a naked valve cover vent tube allow enough crankcase ventaltion?
Yup. In fact, I've done just that when the rings were worn and the excess blowby was causing problems. To avoid painting the engine compartment with oil mist, we connected a length of heater hose to the tube and let it hang down near the road.

2) If I just ran the vent tube to one carb should I install a inline PCV? has anyone done this?
No, if you use the carb port then you definitely don't want a PCV valve in the line. The carb port provides only a very small amount of vacuum (less than 1 psi), which isn't enough to operate the usual PCV valve.

However, there should be a restrictor on the port. If the restrictor is missing, that might be part of your problem.


3) Being that the motor is supposed to be leak free ie: tight valve cover filler cap, sealed oil dipstick. where does fresh air enter the crankcase from?

As I recall, a 73 has no fresh air intake. The crankcase is gradually filled with blowby. Not the ideal setup, IMO, but that's the way the factory did it. I never did understand why they didn't just copy the American system (which had already been in use since at least 1965 or so), but maybe it was patented or something.

poolboy
07-19-2014, 09:57 AM
I've experimented with TR6 emission plumbing for nearly 8 years. This is my current set up.
Depending upon the condition of your piston rings, something like this may or may not work for you.
https://i233.photobucket.com/albums/ee300/poolboy_album/100_0482.jpg (https://s233.photobucket.com/user/poolboy_album/media/100_0482.jpg.html)
I do have a carbon canister, but it is mounted much closer to the gas tank and the only thing connected to it is the gas tank vent.
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6CARBONCANISTER001.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6CARBONCANISTER001.jpg.html)

I'm not sure this is what Randall meant about restrictor, but there is a plastic adaptor that fits on the carb's evacuation port to make the hose from the valve cover nipple fit the smaller diameter nipple on the carb.
If you do not have that adaptor, you can slide about a 1 inch long piece of 5/16" fuel line onto the carb's nipple and then the 15/32 valve cover hose over it.

PanP
07-19-2014, 10:58 PM
Thanks guys for your help. I do have the "restrictors" on the evac ports. They are plastic and serve to allow a larger hose diameter and (without measuring) i believe create a smaller inlet size. I will try your setup poolboy this weekend. Other than not to "green" is there any inherent problem with carb function if I just opt to run the vent hose down like Randall has it? Carbs have been running very lean even with mixture screw clockwise tight and needles nearly full clockwise adjusted. I would imagine blocking the evac ports completely would help to rich-in the carbs.

Poolby, that appears to be a much smaller charcoal can do you know what its from. I like the idea of venting the tank to charcoal still. In fact I would keep all the emission on if I could get everything to work properly, but after a couple weeks and numerous new fittings and hoses, no luck. A sticky float bowl vent valve doesn't help.
Thanks again for the input.
Brian

poolboy
07-19-2014, 11:14 PM
It's from a motor cycle application. I just searched Carbon Canister or maybe Charcoal Canister on ebay until I saw one that I thought would serve the purpose.
Regarding trying to relieve crankcase pressure on a TR6 engine by simply extending a hose from the valve cover to wherever, why don't you just try it ?
After a "spirited drive" for 40 or 50 miles, you should have an answer to your question...the presence of oil outside of the engine or not will indicate the feasibility of such arrangement.
I'm under the impression that the designers knew the answer when they provided a location that could relieve crankcase pressure with a little suction.

TR3driver
07-20-2014, 12:39 AM
I'm under the impression that the designers knew the answer when they provided a location that could relieve crankcase pressure with a little suction.
The whole PCV thing was just a US emissions requirement, nothing more, at least initially (until other areas started requiring it as well). There may be some slight other advantage if it is done right, with a filtered fresh air intake, because it helps keep the inside of the engine cleaner (leftover blowby tends to condense and form gum, varnish and acid) but car makers aren't really worried about what happens outside the warranty period. But up until the US started requiring PCV, Triumph just used a simple "road draft" tube with fresh air (theoretically) coming in through the vented cap.

PanP
07-20-2014, 01:14 AM
The whole PCV thing was just a US emissions requirement, nothing more, at least initially (until other areas started requiring it as well). There may be some slight other advantage if it is done right, with a filtered fresh air intake, because it helps keep the inside of the engine cleaner (leftover blowby tends to condense and form gum, varnish and acid) but car makers aren't really worried about what happens outside the warranty period. But up until the US started requiring PCV, Triumph just used a simple "road draft" tube with fresh air (theoretically) coming in through the vented cap.

Yeah, I know the engine does not want to ingest oil if at all possible and it certainly runs better without vent lines. I would, however, like to catch the blow by in a catch can if possible, but without vacuum it is kind of pointless. Have you seen anyone plum in a catch can on these motors before?

poolboy
07-20-2014, 03:50 AM
I'm not aware of a PCV valve on a TR6 engine after the 1969 model.

I don't know if you'd call a oil separator a 'catch can' but if you do, then 'yes' I had one on my engine for a while and I know some others still do...but I really didn't see the point.
The plumbing is somewhat elaborate, but it is still the carbs sucking on the valve cover relieving the crankcase pressure, but in between the carbs and the valve cover is the separator:
https://i233.photobucket.com/albums/ee300/poolboy_album/oilseparator-1.jpg (https://s233.photobucket.com/user/poolboy_album/media/oilseparator-1.jpg.html)
Once the oil vapor condensed it was separated (supposedly) from water and returned to a fitting welded into the sump.
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6SUMP.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6SUMP.jpg.html)

tomshobby
07-20-2014, 10:13 AM
About 8 years ago I rebuilt the engine in my '76. At the time the addition of the aux oil line was a popular thing to do and one of the initial problems with that was a considerable amount of oil in the intake manifold. Some even had oil dripping from the carb intakes. I installed the same separator from Goodparts and had no problem with oil usage. After a short while I removed the aux line and left the separator. Now with some 50k miles on that rebuild my engine uses no oil. I have no idea if the separator helps or not but I will not be messing with succes so it will stay.

PanP
07-20-2014, 12:20 PM
I'm not aware of a PCV valve on a TR6 engine after the 1969 model.

I don't know if you'd call a oil separator a 'catch can' but if you do, then 'yes' I had one on my engine for a while and I know some others still do...but I really didn't see the point.
The plumbing is somewhat elaborate, but it is still the carbs sucking on the valve cover relieving the crankcase pressure, but in between the carbs and the valve cover is the separator:
https://i233.photobucket.com/albums/ee300/poolboy_album/oilseparator-1.jpg (https://s233.photobucket.com/user/poolboy_album/media/oilseparator-1.jpg.html)
Once the oil vapor condensed it was separated (supposedly) from water and returned to a fitting welded into the sump.
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6SUMP.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6SUMP.jpg.html)

Thanks for the photos poolboy. I don't think I would go to the extra trouble of a return line to the sump. I imagine a monthly maintenance of emptying the can/separator would be required, but at least then you could see the effective results. Does the above installation still only use the slight carb vacuum? or an intake manifold fitting?

poolboy
07-20-2014, 12:59 PM
Just the carbs...maybe Tom did something different.
All that's necessary is to create a pressure differential in order to get the crankcase pressure and the vapors associated with crankcase pressure moving in the direction you want.

tomshobby
07-21-2014, 01:07 AM
I followed Richard Good's instructions including the pcv installation. It has worked flawlessly from sea level to over 12,000' elevation even pulling our trailer.

34004

poolboy
07-21-2014, 12:48 PM
I still have those illustrations if you go the Goodparts PCV route:
This is the plumbing using a PCV valve and his oil separator:
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6pcv.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6pcv.jpg.html)
And this is the plumbing using a PCV valve but without his oil separator:
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6PCV-1.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6PCV-1.jpg.html)
The banjo fitting in both these illustrations is for the 73 and 74 engines.
The banjo fitting for the 75 and 76 is very similar, but it has an additional nipple for the 'diverter valve'
The 70-72 did not have a banjo fitting, just a single nipple fitting for the brake servo vacuum supply.
https://i233.photobucket.com/albums/ee300/poolboy_album/TR6banjo.jpg (https://s233.photobucket.com/user/poolboy_album/media/TR6banjo.jpg.html)