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TR2/3/3A Timing Chain Tensioner - again

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mt10flyer

mt10flyer

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For the 4th time now, my timing chain tensioner broke and wore a hole through the timing chain cover. I have replaced the pin, the tensioner each time. I was lucky enough to find a cover on EBAY the last time because the original looked like Swiss cheese.. The location where the tensioner makes contact with the cover needs to be smooth. Now there is wear there which probably keeps the tensioner (which is just spring steel really) from being able to flex properly. It then fails and rattles around until the chain shoves it though the cover...again. I heard it break while I was on the road and by the time I got home oil was leaking out the new hole like the Exxon Valdez.

There HAS to be a better solution to this. I had a MGB which had an acceptable, heavy duty tensioner in comparison. Of course that would be a relatively involved modification. I am still considering it. Anyone? Ideas?
 
We have 2 issues going on with these tensioners. First, we have had a rash of non-heat treated tensioners, that are the metal equivalent of butter. Then, the chains are not finished like they once were. The links are stamped, and no smoothing is done...so the links are just like chain-saw teeth. It sounds like in your case you also had a sharp edge on the tensioner which also saws into the cover.

Study the new tensioner closely. If you can easily bend it out of shape, then it is not properly heat treated. It should be Rockwell 60 or harder, which will snap rather than bend. Then, take 220 grit paper to the outside of the chain links and polish them smooth, to eliminate all sharp edges. Of course the tensioner should be polished where it contacts the cover, and the cover must also be smooth. The motion of tensioner on cover should be little or none, unless the chain starts to cut into it. The chain wears slowly, so the tensioner should move only slowly along the cover as the chain spreads.
 
The tensioner design seems to work well for most of us. Any abrasions on the chain that would wear out the tensioner?
Hope you you find the cause.
good luck!
Fern
 
Never thought of polishing the chain before, as they used to be OK as purchased. But the ol mad dog
has an idea. When polishing a crankshaft(not the journals) to remove casting roughness, I finish with
1000 grit on a locked sander(set to grind) This yields a mirror finish when done, and is very fast .
CJD is right, be careful of any AM bits like this. Tensioners can NOT be fashioned from old tin cans.
Mad dog
 
This is just a maybe, but when the stud for the tensioner is threaded into its threads on the bear plate there are only about 3 threads that penetrate into the bear plate. I noticed once that the stud was not perpendicular to the bear plate surface, so the tensioner came onto the cover at an angle. I do not remember what I did to fix it. I probably used a different bear plate.

steve
 
sp53 said:
This is just a maybe, but when the stud for the tensioner is threaded into its threads on the bear plate there are only about 3 threads that penetrate into the bear plate. I noticed once that the stud was not perpendicular to the bear plate surface, so the tensioner came onto the cover at an angle. I do not remember what I did to fix it. I probably used a different bear plate.

steve
Click to expand...
Would Locktite on those threads help to keep the stud perpendicular?
 
karls59tr said:
Would Locktite on those threads help to keep the stud perpendicular?
Click to expand...
Originally that stud was pinned with a punch. So if it has been removed, it is very likely that the threads on both the stud and plate have been damaged.
Charley
 
If the stud is bent (not 90 degrees ) replace it and use the serious Loctite threadlocker , a bent stud wont
hit the hole in the timing cover.
Mad dog
 
mctriumph said:
If the stud is bent (not 90 degrees ) replace it and use the serious Loctite threadlocker , a bent stud wont
hit the hole in the timing cover.
Mad dog In Steves post was he talking about the timing cover support called the pedestal or the timing chain tensioner pin? I thought he meant the tensioner pin was bent?
Click to expand...
 
I believe that the stud was installed in factory, onto the plate and "staked" from the
backside to secure it. This was in pre Loctite days. .This is what Charley is calling" pinning"
also referred to as "swaged".
Not every thing done at the factory is to be "worshipped" as gospel. There have been lots
of advances in technology in the last 70 years. I say use them where needed.!!
Mad dog
 
I did not trust my stud, so I gave it a quick tack on the back side of the plate with the welder. Permanent Loctite!
 
You are looking at Charleys post. Scroll up a bit to Steve's post SP3. Steve is talking about the tensioner pin,the shall pin, bending so it throws the tensioner out of alignment causing the timing chain to rub against the timing cover. You and Charlie must be talking about the pedestal stud that just supports the timing cover but has nothing to do with the chain rubbing against the cover which is what Steve is referring to.
 
I'm way late joining all this, but just some thoughts.

First, the old front plates did have the tensioner post machined and secured into place, perhaps welded. The new front plates and tensioner post call for them to be screwed in. I couldn't get comfortable with just loctite, and rather than have it welded (the new plates are aluminum) I did what my machine shop recommended--I peened the back of the post. But guess what? I couldn't trust that because my trusted mechanic friend said I should've use green loctite before peening, so I just used my old plate and worked it as flat and plumb as I possibly could. My new, gleaming "Moss" front plate sits on the shop floor to this day as if I'll use it after I come back reincarnated as a young beautiful female sports car enthusiast 40 years from now.

Second, the only time I wore a hole in my timing cover from a new tensioner was when I forgot to install the proper width washer behind the cotter pin on the tensioner post. I remember watching the oil running down the front of the timing cover and my dad walking up to congratulate me on how quickly I had replaced my suspension bushings, timing chain, front cover gasket and all that stuff. He then looked over my shoulder and said, "That's not a hole is it?"
 
I have seen numerous timing covers worn through, or so badly as to not be trustworthy. High mileage
and poor maintenance takes a toll. A touch with the mig welder and dressed down to flush put it right.
I would say that paying attention to the sealing of the stud and its nut is something often neglected ,
causing one more oil leak than necessary.....
Mad dog
 
Are you guys adding a lock washer on the tensioner pin? My pin wallered out so I taped the hole & got a new pin put it stuck out the back side of the plate . I added a lock washer which brought it up flush on back of plate & the pin tightens better. Is that going to hold the tensioner out too far or do you think I’m ok. I’m going to weld it on the back side also.
 
I’d be careful before doing anything with that pin that would move the cotter pin hole forward, and the tensioner as well.

The Brits machined very little clearance under the cover and if the tensioner rubs on the cover, it will wear a hole into it. I speak from personal (shameful) experience.

I like that you’ll tack weld the back side, as I’ve always worried about what would happen if that pin ever came loose.

I have a beautiful new aluminum front engine cover, sitting in my garage with a new tensioner pin screwed into it. During my last rebuild, I didn’t have the courage to use it, because I just wasn’t comfortable the way that tensioner pin fit. When I put it together, I used red lock thread. One of my friends was agonizing that I didn’t use what he referred to as permanent green.

Good luck. I’m sure you’ll be fine, but I would honor that clearance.
 
I think the original stock pins were just screwed in, tightened on the hex bolt, and peened on the back. I've never trusted that I could produce a good effective peen with my hand tools. Some of you folks out there may be pros, but I'd rather see a weld like MH is doing. I've also wondered the damage if that pin ever came out, but that's just me.
 
KVH said:
I think the original stock pins were just screwed in, tightened on the hex bolt, and peened on the back. I've never trusted that I could produce a good effective peen with my hand tools. Some of you folks out there may be pros, but I'd rather see a weld like MH is doing. I've also wondered the damage if that pin ever came out, but that's just me.
Click to expand...
When my pin worked loose the tensioner rattled around until it wore through the front of the chain cover.
 
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