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Triumph TR6 - Valve adjustment problem
Last year I had my TR6 head rebuilt and unfortunately the machinist did not know that new guides must not be too tight with valves. The results: I start the engine for a warm-up and to check that everything was OK and 2 ehxaust valves seized in their guide. After another rebuilt I notice that the valve lash adjustment on one valve was extremely noisy and settle things by adjusting that valve with the engine running, it was far more too slack but I am sure it was properly set when cold prior to start the engine. My question does a sticking valve in a guide could have ruined the camshaft. does someone have any idea...
|Jean G. Catford|
I don't think a sticking valve would damage the camshaft.With the valve open, you actually reduce the load on that lobe. The lifter could be damaged by slamming into the stuck valve I suppose. The possibility of the piston hitting the valve if it was open far enough exists. You would know this immediatly by a misfire or popping noise in the intake, or popping in the exhaust. A compression check would prove if all valves are seating well.
I restored a TR6 a few years ago, and had difficulty getting it to idle correctly after a fresh rebuild. The engine was only developing about 12in of vacuum, instead of 18-20.After removing & resealing the intake manifold and carbs, I reset the valves per the manual two or three times with same results. I finally readusted the valves by bringing each piston to TDC, and setting the valve lash. This instantly cured the low vacuum and idle problem.
I will be adjusting my valves shortly and your comment re doing it by the book and then by each piston at TDC intrigues me.I have done it by the book after a top end rebuild. Could you please explain what you mean by the TDC method. Are you adjusting the 2 valves for that piston that is at TDC? I get the impression from you that it is better. Is there an article on the WEB that I might go to and save you some typing?
Oh Ya...The temp. in my garage is around the freezing point...should I wait till warmer days so that I do not get an error in the gap because engine is so cold? In other words is it better to set valve clearance at say 70F as compared to 35F or does it matter?
Likewise I just adjusted mine (twice) before the fresh motor goes back in. Am curious too,Also a ? anyone, on valve position, at TDC are all valves in a neutral position? Want to make sure the Dist. goes in right.
Yes, each piston is brought to TDC on firing stroke, following the firing order/position of the dist. rotor. Check piston position with a screwdriver thru spark plug hole as you turn the crank by hand. When you are certain you have TDC position, adjust the intake & exhaust valve lash for that cylinder. I go over them a second time to double check myself.
My experience with the TR manual procedure resulted in too tight valve lash, resulting in insufficient vacuum.( on a 73 TR6)I don't remember actual dimensions.
Don Kelly; The distributor position should be set while #1 is at TDC, and timing marks are aligned. Follow the TR manual for that one. When the piston is at the TDC position of the firing stroke, the lifters for that cylinder should be at the lowest point of the cam lobes. Is this is what you mean by neutral?
Rick Crawford; I'm not sure about the temperature issue as it applies to the valve procedure. I know it makes a difference when you are mic'ing bearing journals and pistons/bores. I usually work in 55-60 deg F minimum temps during the winter. Sounds like you need a torpedo heater.
|Pete thanks for the reply. Maybe I will wait till a little warmer..can not drive her anyway. This cabin fever is really getting to me. Last summer I had an owner of a 3A who lives around the corner say to me that it sounds like your valves too tight. He said not enough noise from the tappets...like what you said. The gap from manual is 10 thou. Had 2 heaters in garage when doing the restore.|
Interesting alternative from the manual.
No argument with Pete, but here's another way, that may be easier - the Rule of 13.
Number each valve from the front, 1-12. Note which two valves are fully open, and subtract the number of each from 13. These are the numbers of the valve pair that is now on the back of the cam, fully closed and ready to be adjusted. To move on the next pair, turn the crank, about 1/3 of a revolution or 120 degrees.
Note 1. The pair of valves you adjust each time will NOT be on the same cylinder! I mark the adjusted valves with a dab of vaseline, so that I don't lose track.
Note 2. Works for four cylinders - Rule of Nine, and would for five with Eleven. See how it works?
I know about the cyl. #1 @TDC for dist. with timing marks aligned to install dist. I thought that if the crank goes around 360 again #1 won't be at TDC and I didn't want to install dist at that position. The screwdriver trick gave me an idea. Thanks
Do that again but move your lips more slowly. Do you sub. each valve from 13. So if 6 is open(push rod up) you subtract that from 13
and adjust 7?. Have I got it?.
I am still scratching my head too...and I did not have a lot of hair to start off with!
Your right about the 180 off problem. Hold your thumb over the spark plug hole, you will only develop compression while coming up on the firing stroke. This will assure you won't put it in 180 off.(unless the drive gear is on wrong, I ran into that once)
Don't even go there.
Take care of your hair!
You have it, Don.
1 up - adjust 12
5 up - adjust 8, and so on.
Or for four cylinders, rule of 9 (it's always one more than the number of valves)
1 up adjust 8
6 up adjust 3
Each valve is numbered consecutively from the front.
If an engine has four valves per cylinder, treat each pair of exhaust/inlet valves as one and adjust together.
You can also imagine of a mirror across the middle of the engine - adjust the valve that is the 'mirror' image of the 'up' valve. This has the same effect and is the reason why it works! An engine must be balanced in the way that its' cylinders fire, so when one is on the firing stroke, the 'mirror' cylinder must be on the opposite end of the cycle
This thread was discussed between 13/02/2002 and 22/02/2002
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