Thread: Valve stem seals

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  1. #1 Valve stem seals 
    Ole Boy
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    I'm looking for the experts to explain what the valve stem seals are for, and why some engines have them and others don't. Actually I am curious to know if the 3.5 litre engines of the late 70's and early 80's should have these on the intake and exhaust valves.

    I seem to recall when I owned my 98 Land Rover Discovery, that there was some issue of "sticking" valves, and either you removed or added valve seals as part of the solution... ???
    1979 Triumph TR8 Coupe
    1981 Triumph TR8 Convertible
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  2. #2  
    Little Brit
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    My 1980 tr8 does not have any. I was surprised to see that as I am use to motors that do. They are there to keep excess oil from entering the cylinder. I have my heads off now and dont plan to use any.
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  3. #3  
    Brit
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    The SD1 and TR8 didn't use them. The later Rover engines have a positive type stem seal. I used the Rover ones on mine since I have late heads. Got them from Rovers Richmond since parts stores don't even know what you are talking about.

    If the guides are not worn I don't think you would have any oil consumption issues without them. I always hate the burned oil buildup that acumulates on the stems so I use seals.
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  4. #4 Valve Guides 
    Little Brit
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    I am just now getting my TR8 back in shape after a 1 1/2 year "rest". The last thing I had done to the car was to replace the head gaskets. Now I am wondering If I did something stupid by not replacing the valve guides while the heads were off. I am getting quite a bit of smoke out of the breather, and I get a puff of white smoke out of the exhaust when I "goose" the throttle. Am I on the right path here? Would the installation of valve guide seals "bandaid" this problem for a while?
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  5. #5  
    Young Brit
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    The Rover engines in TR8's did not have them installed from the factory. The guides will need to be cut down to install the seals. I use them on my V6's and V8's on the intake vales. I never heard of them installed on the exhaust valves, but, I guess some engines might have them. There is very little vacuum to suck oil down the exhaust valve stem, but, there is alot more vacuum on the intake valve.

    I would not waste my money installing them on a worn out engine as a band aid to reduce smoking. Others will disagreed, most likey. As the heads need to be removed to install the seal correctly. They will more than likely be smashed to bits if the guides are not cut down. YMMV
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  6. #6 valve guides 
    Little Brit
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    Yeah, I kind of figures. I guess it's "off with the heads" again. Lesson learned.
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  7. #7  
    Ole Boy
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    Your description of the symptoms does not exactly seem to be valve guide issues. I would expect more "blue" smoke on overrun/deceleration and when you "goose" the throttle, not white. Anyway, it still might be simple enough to experiment with the stem seals before pulling heads again.

    There are 2 types of stem seals, the first is the old style from pre-SD1 (ie pre-76 engines). These are flat circles of thin rubber, look sort of like tire inner tube. These simply wipe the valve stems and may not be as efficient as later Land Rover style "positive type stem seal" as Underdog described. Those are like a rubber "cap" that slips snugly onto the top of the valve guide. Later guides are machined to ensure the "cap" stays in place, but they still do fit quite snugly on the TR8/SD1 era guides.

    Using (for example) a Lisle 16750 spring compressor and a 19700 valve holder to keep the valves closed, you can install all 8 intake seals in a single day... search amazon.com for sample pricing...
    1979 Triumph TR8 Coupe
    1981 Triumph TR8 Convertible
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  8. #8  
    On the later model motors 4.0 , 4.6 they put valve stem seals on for emissions reasons only. When they did this they not decrease the clearance from valve stem to guide, which caused sticky valve problems due to lack of lubrication.

    If you intend to use the valve guide seals, the valve guides need to be opened up to the correct clearances to eliminate this problem. If emissions is not a problem, there is no need to install the valve seals.

    The 3.5 and 3.9 never came with valve seals.

    Thanks
    Woody
    The Wedge Shop
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  9. #9  
    Ole Boy
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    And Land Rover did their own "fix" for those sticking valves in the 4.0/4.6 motors. They developed new valves with "carbon cutting" stems, and also there were instructions to ream the existing guides slightly larger. Doing that of course makes those oil seals even more important!
    1979 Triumph TR8 Coupe
    1981 Triumph TR8 Convertible
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