TR4/4A Better Breathing TR4 vs. TR4A Valve Cover

[jimitro]

My TR4 is next to the treadmill in the garage with the hood up and I keep coming up with these crazy what ifs!
I currently have the original valve cover on with the oil breather cap. Would the performance benefit if I switch to TR4A valve cover with the breather hose being routed to the air filters? Thanks

 

[TR4nut]

Well, thats funny, I actually thought about converting the other way - but I don't have the treadmill in there as it would interfere with my beer fridge.

I have a 4 with the vent routed through the filters. I don't know if that is superior to a breather cap (I doubt it) but here is a practical thing to think about: The parts like the flame trap splitting the hose to each filter is NLA I think, but can be had at times on ebay. The filters, though, are always pricey - much cheaper to go with filters that don't have that breather connection.

They do sell a mini filter that ties directly to the side vent on the 4a style cover, but I still think on the performance side nothing much is happening there - can't be all that much backpressure in the vented cap you have.

 

[Geo Hahn]

[ QUOTE ]
...Would the performance benefit if I switch to TR4A valve cover with the breather hose being routed to the air filters?

[/ QUOTE ]

If you also eliminate the road draft tube it would likely improve the overall chassis lubrication... i.e. you may find oil leaks in places that seal well now.

I sort of went the other way: I kept the sealed cap on the valve cover and the 2 tubes to the air cleaner (mainly to preserve the look of originality) but added the TR3/early TR4 road draft tube to the block (the later engines with the closed system do not have this tube). This noticably reduced oil seepage and yet very little oil goes out the draft tube.

Bottom line -- I don't think there would be any performance gain and the system you have now is the best (being what was originally designed for these engines).

 

[jimitro]

Thanks Randy and George for your input. I am keeping the road draft tube on the engine. The Long Flo filters I just picked up have adapters for the breather tubes. If I go this way, is a flame trap necessary? Thanks

 

[Geo Hahn]

[ QUOTE ]
...If I go this way, is a flame trap necessary?

[/ QUOTE ]

I would think it a good idea as (in theory) the valve cover can suck 'air' from the carbs as well as push fumes into them.

 

[martx-5]

I've discussed this before in some other threads about the PVC system, and quite frankly, a correctly operating Positive Crankcase Ventilation system is not a detrement to your engine, but rather, it is good for the motor. It will keep the internals cleaner. It sucks out the unwanted gases that get by the rings. The oil stays cleaner. Engines run better with some vacuum in the crankcase, rather then pressure. Operating properly, it will keep the oil leaks down better then just the road draft tube. All that does is relieve the pressure build up and it relies on the forward motion of the air past the tube to create a vacuum. It doesn't do that so good, and when your standing still idling, pressure in the crankcase is building.

I'll definetly be putting one on my TR3 engine when I get to that part of the restoration. However, the systems that I see on the 4 cylinder TRactor motors leave alot to be desired. I don't think they are as efficient as they could be. The trick is to get a proper PCV valve for the size of the TR engine and route the plumbing correctly. The valve itself should be a fairly easy acquisition, as there are plenty of styles available in the 2.0-2.2 liter engine size. I've been looking at various routing options, but haven't yet decided what would work easiest on the TR. The function of the valve is to let a small amount of (metered) air through the valve at high vacuum situations (idle and decel). During low vacuum situations (wide open throttle), the valve opens all the way. When the engine is shut off, or there is a backfire, the valve shuts to prevent any type of flame from entering the engine. It's all pretty seamless and quite reliable with only an occasional valve replacement. /ubbthreads/images/graemlins/driving.gif

 

[Alan_Myers]

Hi Jimitro,

Hey! The TR4 open breather circuit does such a wonderful job undercoating the car, don't know why you'd ever want to change it! /ubbthreads/images/graemlins/smirk.gif

Seriously, I've been looking at the same thing and thinking about my options. I'm putting a catch tank in my TR4 and have some concerns, because either the breather tube or the pcv setup used on the TR4A will create a small amount t of vacuum to help pull contaminant vapor out of the crankcase. That won't be the case with the catch tank/breather setup I'm going to need to use.

I don't think any of these setups will have any measurable effect on performance. So, I've toyed with the idea of setting up a true crankcase evacuation circuit, using an electric vacuum pump and a vac reservoir/catch tank.

I'd want to use an electric pump instead of the belt driven used on big V8s, because belt drive would rob some HP and be a hassle to install. My idea is to create a little higher vacuum than would ever be present in any of the TR4/4A setups, maybe 7 inches worth.

A crankcase vacuum setup is used on some high performance cars because it helps the rings seal better for a little better performance. I don't think the 21+ inches of vacuum sometimes used on high performance V8s would be necessary with the TRactor motor, so have even thought it might work with a passive setup, just a one-way sealed circuit that allows air out and let's the piston action create it's own vacuum, which is stored in a reservoir/catch tank. That would be ideal... no electrical pump to burn out and fail!

If a pump were necessary, I understand many types of elec vac pumps don't hold up well in an oil environment. Apparently, there is a Cadillac elec vac pump that works well, though, and is probably more than enough to evacuate the crankcase on a TR. Unfortunately, it's rather pricey to buy new and sells for a lot even used on eBay. The exact amount of vacuum can be controlled pretty easily with a vac relief valve and breather.

On the other hand, maybe I just have too much time on my hands, to think up things to try! /ubbthreads/images/graemlins/cool.gif

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[TR4nut]

Regarding adding a more modern PCV valve to the TR motor, I think the thing to sort out is the vacuum source. This would normally be directly on the intake manifold like on a 4A. I'm not sure you would get the same desired effect routing through the air filters. Not a PCV valve expert, but would think they are designed for certain vacuum levels which may not be attained on the filter side of the carbs?

 

[PeterK]

Alan,
I am adding a TR6 dual MC/servo setup to my 4A and have a catch can too. Have you any thoughts about how I could/should split/don't split the vacuum source? I was planning to route the servo straight to the manifold vacuum through a non-return valve; then output the valve cover port through the PCV and then to the catchcan (filtered).

Do you really think I would need a vacuum source for the PCV? Or is my setup OK? No plans for a draft tube although I have seen a race setup (Revington) with the draft tube post routed to a catch can as well as the PCV.

Ideas or suggestions?

 

[Andy Blackley]

Gents: I think the Triumph designed PCV system, using the Smiths "mushroom" found on the TR-4A and the TR250 is hard to beat. It was designed to work with these cars. Crankcase fumes are drawn through the valve into the manifold, and fresh air is drawn into the engine via the air filters. The manifold vacuum source is vital. The connection to the air filters is only to draw fresh air into the engine.

 

[jimitro]

Thinking more about a possible set up on using the TR4A valve cover on my TR4, what if you run a hose from each air filter into a t-adaptor then adding an in-line pcv valve coming off the t to the valve cover? Does this make sense?
Thanks

 

[TR4nut]

I think what you describe pretty much duplicates the setup I have on my TR4 except I still have the original flametrap tee instead of the modern replacements. It should work, except I can't say with any knowledge if you've improved the crankcase ventilation over what you had before.

Randy

 

[Andy Blackley]

[ QUOTE ]
Thinking more about a possible set up on using the TR4A valve cover on my TR4, what if you run a hose from each air filter into a t-adaptor then adding an in-line pcv valve coming off the t to the valve cover? Does this make sense?
Thanks

[/ QUOTE ]
The setup you propose might work provided at a. you use an oil filler cap that allows air to enter the engine, and b) you can find the right PCV. Buying a PCV in a bubble pack from the local auto parts store is a shot in the dark. BTDT.
These valves are designed to open with manifold vacuum and are calibrated to work with the PCV designed for that specific engine application.
The best systems need a connection to the manifold at some point BEHIND the throttle butterflies to work properly.

 

[Geo Hahn]

[ QUOTE ]
...The best systems need a connection to the manifold at some point BEHIND the throttle butterflies to work properly.

[/ QUOTE ]

Too true. The stock set-up on a TR4 (which is a lot like what you describe) relies on the rather anemic vacuum available through the small snouts (1/4"?) on the air filters.

I'll stand by my original comment that (enviromental concerns aside for the moment) you already have the best system.

 

[SpannerMan]

[ QUOTE ]
These valves are designed to open with manifold vacuum and are calibrated to work with the PCV designed for that specific engine application.
The best systems need a connection to the manifold at some point BEHIND the throttle butterflies to work properly.

[/ QUOTE ]

When I was looking at the same thing some time before the holidays for my TR6 with SU H6's (there is a thread on here if you want to do a search) I was wondering about T'ing a PCV valve into the brake booster hose on the manifold. I don't have the stock PCV port- looks like it has been blocked off either at the factory or by a PO. Does anyone think the brake hose T idea might work? You would have the PCV valve in the hose off the valve cover, and then T'd into the brake booster. It's a bit of a narrow hose, and I was worried about the flow capacity I think. Pete

 

[Alan_Myers]

[ QUOTE ]
Alan,
I am adding a TR6 dual MC/servo setup to my 4A and have a catch can too. Have you any thoughts about how I could/should split/don't split the vacuum source? I was planning to route the servo straight to the manifold vacuum through a non-return valve; then output the valve cover port through the PCV and then to the catchcan (filtered).

Do you really think I would need a vacuum source for the PCV? Or is my setup OK? No plans for a draft tube although I have seen a race setup (Revington) with the draft tube post routed to a catch can as well as the PCV.

Ideas or suggestions?

[/ QUOTE ]

Hi Peter,

I really am not sure I can be much help. In my earlier response, one thing I failed to mention is that I have no vacuum source on my car... It's fitted with Weber DCOE carbs and a Warneford manifold which I don't want to imbalance with any vacuum ports. For that reason, DCOE fitted cars are usually converted to a mechanical advance only distributor and manifold vacuum ports are closed off. (I have run DCOE successfully with vacuum ports in the manifold, but it makes them difficult to balance.)

In addtion, a higher duration cam such I'm using might reduce available vacuum at low rpms in particular. Since a cam upgrade is often combined with a Weber installation, this is probably another reason DCOE installations are not normally fitted with vacuum sources.

So, those are the reasons I'm looking at alternatives, such as an electric vac pump of some sort.

My primary purposes for a vacuum circuit on the crankcase is to improve cylinder sealing and draw off some of the contaminant fumes typical in any crankcase. But, it's entirely possible I'm just over-engineering the whole thing! /ubbthreads/images/graemlins/crazy.gif

It sounds like your setup should work. I'm working without a PCV and was thinking instead of using a catch can that doubles as a vac reservoir, controlling the amount of vac with a release valve/breather that essentially does the same thing, and routing hoses from the valve cover and the crankcase (the latter with an oil trap). The only thing I'd be concerned about with your design is that you might want to be careful that there's no way traces of engine oil might find their way into the vacuum side of the brake servo. I don't know for certain, but that might be a problem.

Elec vac pumps and vac reservoirs are used a lot in power brake/servo situations like yours, when a high duration cam that tends to reduce available vacuum at the manifold in low and mid rpm ranges, in turn effecting the brake servo. So, one manufacturer of the elec. vac pumps is Stainless Steel Brakes. But, their pump is pricey and not really designed for an oil rich environment like crankcase evacuation. It's really just intended to supply a brake servo.

I know at least one alternative source of vacuum: the exhaust. A drag racer trick for crankcase evacuation is to weld a couple 1/2" approx. tubes into the exhaust. Those have slanted tips cut on the ends and as exhaust gases flow by a vacuum is created (much like the larger open air crankcase draft tube on the TR2/3/4). Of course, using the exhaust that way is not street legal or very environmentally correct, since it will pull some fine oil mist out of the crankcase and send it directly into the exhaust. I really can't say if this would work for brake servo purposes.

Hope this helps!

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