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TR2/3/3A Valve Knock Question

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HighAltitudeTR3

HighAltitudeTR3

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I have a knock coming from intake on #4 Cylinder. If I tighten the rocker arm adjustment enough (more than prescribed) the sound goes away. I loosened it back to about .009 and the sound is less but not gone. What's going on here? I've spent some time with the Tech support at Moss and we couldn't really pinpoint what this test has determined....
 
You'll risk burning a valve if you reduce the valve lash too much...The valve needs time to sit on it's seat to cool off.
 
Thanks Poolboy. I only set it there for a minute, I was afraid it would cause damage. But how can I remedy the "knock" that goes away when I tighten the rocker arms? The Moss rep was suggesting a sticking valve?
 
It could be that the spark plug wire is bad.
I had a noisy valve and I couldn't figure out why, so I just lived with it. Then one day for an entirely different reason I decided to check the resistance of the spark plug wires..one was way higher than the others.
I replaced it and noticed the loud valve fell in line with the rest.
 
Oh well.
You can test for that sticky valve theory with a compression test.
If the valve is sticky, which means it's not completely closing, the compression will be lower.
 
I have good compression across the board. Good and even.

Tightening the rocker arm beyond spec removes the backlash and in theory opens the valve more? I'm having a hard time picturing what is going on. Why the noise disappears
 
Check to see if you have a divot under the rocker arm. If so, then setting the valve lash with a flat feeler gauge won't take into consideration the depth of the divot and you will actually wind up with more lash then the gauge reads.
 
Bent pushrod possibly?

Cheers
Tush
 
The valve won't be opening more with less lash, just longer causing it to spending less time cooling off on it's seat
 
Talking rockers...

The tip of the valve wears a groove into the tip of the rocker arm. This is not visible unless you remove the rocker shaft and look at the rocker tips from the under-side. Given time, all the tips will wear a respective groove into their arms. Now, once the rocker arm is grooved, a feeler gage does not give an accurate clearance. The flat gage bridges the groove, basically ignoring the extra clearance caused by the groove.

This means your rocker arm is heavily worn. If you want to buy time on a rocker shaft rebuild, you can set your valve clearance using a dial gage. The gage reads the movement of the tip of the arm, and thereby accounts for the groove wear.

Edit: this is +1 to what Art said.
 
Thanks guys!! This seems almost too easy. Makes me nervous. Is my "test" proving anything else?

I am replacing the rocker arm? I should probably do all 8...
 
You can often dress the ones you have with a grinder to remove the wear groove. Your shaft will likely be worn, and the rocker bushings will likely be worn. Once you get it apart you see what you are dealing with and repair/replace as necessary. You may need all 8 rockers...but you may be able to save some too.
 
If one rocker is worn they are all probably worn...
Just remove the whole rocker arm assembly from the car and take a good look at the tips that contact the valves, if you feel a groove it is time for a rebuild.

I recommend that you pack the whole mess in a box and send it off to these guys:
https://www.rockerarms.com/index.html

To save you some time, here is the applicable Tr link in that web site:
https://www.rockerarms.com/pages/triumph.html

M.
 
Ok, just popped the rockers off. Not really too warn. It's a little polished. I put a straight edge on it and the worst one might off at most .0001". Not much.

So any thing else that might cause this? I did press down on the valves when I had the rocker off. None of them were stuck, but the one giving me a hard time sounded "squishy"
 
I just replaced the rod bearings. Main bearings are good. Sound goes away with accelerating and warm engine. Was exploring the idea of piston Slap or wrist pin but this test threw me a curveball.
 
The actual rocker shaft was not pitted and scared on the bottom? The engine was probably gone through then or did you look at the tips only. The rocker also has a brass bushing that wears out so bad it can be missing. I have seen engines were one or more setting was reduced to .03 setting warm to quiet a loud engine and the car ran fine for years, but that is one of those things people do not talk about.

I must admit I am surprised the rocker assembly is in good shape if you did not have it done. If you have the rocker shaft removed still, slid the rockers side to side into the spring and look closely and make sure before you re-install.
 
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