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Discussion Starter #1 (Edited)
I shared a version of the following embarrassing story with Marc T. earlier and thought it would be best shared with the group:

I want to encourage you to check your timing chain tensioner bolt torque (after a complete rebuild). Mother's Day, I took my Duetto out for a little 'exercise'. As I accelerated up the long hill on Lead, pronounced Leed Mountain Road, by the locals, I heard a worrisome, 'whirring' sound. I suspected that possibly the NOS fan belt had separated or maybe the tachometer cable was getting ready to seize or any number of other scenarios that went though my head...

Long story short; at the top of the hill, I pulled over and the car just stalled -huh. I opened the hood and checked that everything looked fine. When I briefly turned the key, there was a bad metallic sound and shaking from the engine, which stalled or didn't even turn over. I called JC Taylor, fortunately I had their 'towing service' number in my cell phone; right at 5 pm on Mother's Day. 20 minutes later a flat bed showed up, TTL!

The Duetto was shackled to the flatbed of shame for the second time in the 36 years that I've had it. The first time was the day I 'bought' it, as a failed restoration project. The previous owner had just started the restoration project on the Duetto when I offered to trade him my nice 75 spider for the Duetto. At first he refused but after his MGBGT suffered an electrical short and interior fire, he relented and took me up on my -at the time, generous offer .

Once the Duetto was back home in the garage, I pulled the valve cover....only to find that the timing chain was so loose it was drooping between the sprockets, doubled up upon itself at the crank and the tensioner was most of the way retracted. I now know that the whirring sound was the chain contacting the aluminum timing case cover. My heart sank as I had just finished rebuilding this engine about 1,100 Km ago. I remember thinking as I tightened the tensioner bolt, that about the last thing you want to do is strip that bolt, as my Alfa mentor Alex Bardi had done 40 years ago! Well, leaving it too loose is just as bad or possibly worse.

I pulled the cams out, reset the timing chain so the master link would be between the cams with the engine at TDC, lobes out on #1, etc. With cams reinstalled, I checked, only to find the valve clearances were still good. Just to be sure, I ran a compression test and all four cylinders came up equally within 5 psi. I drained the oil and aluminum shavings and changed the oil and filter (with only 80 miles on them). Fortunately all went well after the oil and filter change, the engine runs fine.

I suspect the tensioner fully retracted, either when the engine stalled or when I attempted to restart it on the side of the road and I heard bad noises. Without stripping the fastener you might want to check the torque on your tensioner bolt. Would anyone know if there is a torque specification that covers the tensioner bolt? I've noticed that several fasteners, especially on gasketed surfaces, were loose after heat cycling the engine, so it might be a good idea to check every fastener you can for tightness. If not, you may want to keep the tow service phone number handy in your cell phone.

While I had the cam cover off, I stripped the cover from my spare engine and wrinkle painted it. Now the bolt bosses on the front of the head have matching cam cover bosses to mate up with and for the first time in 40 years, I did not 'hi-lite' the Alfa Romeo script in silver.

Mark
 

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Excellent commentary and admission of "failed-to-check". Others need to READ THIS!
 

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I am not sure what went wrong in your case, maybe you forgot to tighten it altogether?

there is no torque for the tensioner bolt, but do it too tight and you could crush the divot into which it fits and deform the sleeve the spring fits into (especially if the bolt pin hasn't located into the hole of the divot thingy)

A small wrench and tighten it with feeling, you are just locking it in place, not trying to rip the head off the bolt...!...;)

In actual fact, there should still be a thread or two visible when tight.
tensioner bolt (2).jpg
 

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Most common fault is loosening the bolt too loose so the locking wedge disengages from the tip of the locking bolt. Chain tension adjustment then drops the wedge down into the sump. Retightening the bolt then either does nothing, as it seats on its threads, or only lightly locks the tensioner itself, allowing it to MOVE later. Easy way to tell if wedge is lost is to note if threads show on the bolt when tightened. No threads showing= lost wedge. The wedge in the sump does no harm there, I've found several on engines I've rebuilt. However, fitting a new one, head on the block, is a real pain. Trickery is involved in the "lost-wedge" fix.
 

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A year or two ago I was working around the distributor of my Spider and I noticed that tensioner bolt was missing. I managed to "fish" the wedge into the correct position and I fitted another bolt. I must have forgotten to tighten it after I had been experimenting with alternate valve timings and that was a few weeks earlier. Sometimes lady luck smiles.
 

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A year or two ago I was working around the distributor of my Spider and I noticed that tensioner bolt was missing. I managed to "fish" the wedge into the correct position and I fitted another bolt. I must have forgotten to tighten it after I had been experimenting with alternate valve timings and that was a few weeks earlier. Sometimes lady luck smiles.
That was a good day, did you rush down and buy lottery tickets?
 

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Discussion Starter #8
I am not sure what went wrong in your case, maybe you forgot to tighten it altogether?
View attachment 1629242
As mentioned "I remember thinking as I tightened the tensioner bolt, that about the last thing you want to do is strip that bolt, as my Alfa mentor Alex Bardi had done (on his car) 40 years ago!" The 'funny' thing is, he first unscrewed the tensioner too far and the little 'wedge' with the hole in it, fell into the oil pan! Then to add insult to injury, he stripped the threads out of the head with the tensioner bolt. That is one bad week! I usually err on the 'over tightening' side of things, too and in my case, I would say 'snugged' the tensioner up pretty good (but obviously not good enough).

Now I am wondering about the tensioner. When rebuilding the engine, I used a John Norman rebuilt 1600 head that I bought many years ago. It came with new cams, valves, springs, shims -the works. But it didn't come with a tensioner. The new head had bosses on the front for the valve cover. My original head and valve cover were the older style -without bosses. I swapped the tensioner from one head to the other thinking they were otherwise identical but I had no tensioner from a head with front bosses for comparison. I hope they are the same!

Uncle wrote, "I've heard of wedges installed upside down. That won't work either." If I understand what you wrote; I would call 'backwards'. It seems like you can install the 'wedge' on the protrusion and spin it upside down, 180 degrees and it still works. But put it on the protrusion backwards and it no longer has sides parallel with the tensioner's slot for it to 'wedge' into.

Ed, if you drove that car for a few weeks without a tensioner bolt; all I can say is that "you must have been living Right"!

Mark
 

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I'll share my "re-learn" moment.
I replaced the rear flexible section of brake line on my duetto.
For the life of me, I could not get the rear brakes bled.
Bubbles, bubbles and more bubbles in the one man bleeder clear tube.
So, I thought I had a bad Master Cylinder.
I buy a new one and install it and the same thing happens!
I call an Alfa buddy and he says, "Remember that little trick I told you about wrapping plumbers tape around the bleeder valves to keep air out?"
"OH yeah, that's right!!"
Taped them.
5 minutes later, the brakes are bled!
Well, now I have a spare brake Master Cylinder!
 

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I'll share my "re-learn" moment.
I replaced the rear flexible section of brake line on my duetto.
For the life of me, I could not get the rear brakes bled.
Bubbles, bubbles and more bubbles in the one man bleeder clear tube.
So, I thought I had a bad Master Cylinder.
I buy a new one and install it and the same thing happens!
I call an Alfa buddy and he says, "Remember that little trick I told you about wrapping plumbers tape around the bleeder valves to keep air out?"
"OH yeah, that's right!!"
Taped them.
5 minutes later, the brakes are bled!
Well, now I have a spare brake Master Cylinder!
Worth noting that the use of teflon tape as a thread sealant for brake lines is a bit controversial. There are liquid thread sealants that don't have the potential to have pieces break off and get into the caliper.
 

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If you do in fact drop the wedge, its easy to put back into place when you take the large allen-head plug out of the end of the head -- the plug that holds the spring inside the cylinder
 

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Some time ago, I helped a friend who lived nearby swap the engine in his Junior Spider. Just as we were starting up the new engine, I suggested we follow the owners' manual about setting the timing chain tension... leave the tensioner free, idle the engine to self adjust tension, then tighten the tensioner lock bolt.

DON'T DO THAT! The engine died almost instantly, the chain skipped and the cam timing was lost. No damage, fortunately.
 

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Discussion Starter #14
...follow the owners' manual about setting the timing chain tension... leave the tensioner free, idle the engine to self adjust tension, then tighten the tensioner lock bolt.
That is one way to tension the timing chain that I have never done. My buddy Alex showed me how he had been taught (after all his issues) to use a pry-bar on the tensioner -to extend it. Then lock the bolt in place, without stripping it.

About 45 years ago, after rotating the tires on my MGB, I noticed a strange wobble as I pulled off the highway exit ramp. I got out to investigate and found there was only one lug nut still barely holding my left front wheel on! Somehow, I forgot to torque those nuts. I hope this never happens to you. If it does, you can take one lug nut from two other wheels and put them on the wheel that is missing nuts and slowly drive on.

Mark
 
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