Chain Tensioning

4488 Views 29 Replies 15 Participants Last post by otteud96, 12 mo ago

Silver78

Discussion Starter · Aug 31, 2007

I have a chain tensioning question regarding my 78 spider. Upon deceleration at 2000 RPM, I'm getting a rattling/chatter/vibration that sounds like it's coming from right under the cam cover toward the front of the engine. It's only for a few seconds and goes away once RPMs dip down below 2000. I assume (hope) the chain tension needs adjustment and it is nothing more serious than that. Car only has 26k original miles. Thought I would start there, does that make sense? Any other thoughts on what the problem might be?

I have been looking up how to adjust the chain and according to the manual you: #1 remove the cam cover (easy enough). #2 loosen the chain tensiong securing screw (looks like a bolt to me, but ok). #3 Engage 5th gear, move vehicle back and forth keeping chain stretched, and then lock (retighten) the chain tightner securing screw (bolt).

Will you get the same tension whether you push the car forward and hold it or backward and hold it? If all you need to do is push the car while in gear to get tension, why do you need to take the cam cover off? I'm not a big fan of the manual, is this the right proceedure, it sounds to easy? Can the tensioner be "bad". How would I check it?

Just thought I would double check before I started messing with this in the morning.
Thanks, Gary

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Alfacliff

· #2 · Aug 31, 2007

you rock the car to get the chain tensioner spring to extend the tensioner. the spring isnt strong enough to pull the chain slack from between the cams or cams and engine by itsself.
I usually use a large screwdriver to pry the tensioner out, then tighten and check tension on chain. a coupla weekends ago, my tensioner backed off, must have been too loose on the bolt, and made a lot of noise. if you rock the car make sure the chain dosnt skip a tooth on any sprockets.
cliff

Andrew

· #3 · Aug 31, 2007

Rocking backward will tend to loosen the chain, so be careful and watch what happens; tighten after rocking forward. Once I get the chain about how I want it, I use a small crowbar to "help" push the tensioner out (levering against the intake cam), then lock the bolt down at the same time. Rotate the engine by hand, or in gear a few revs, to make sure the chain is right. Then spin it on the starter with the ignition disabled to make sure all's fine, then button it up.
Andrew

Alfacliff

· #4 · Aug 31, 2007

when loostening the bolt on the adjuster, no more than one turn, one half turn should be enough, if the block on the end of the adjuster bolt comes off, you will not be happy.
cliff

papajam

· #5 · Aug 31, 2007

Andrew said:
Rocking backward will tend to loosen the chain,...

Andrew is absolutely correct here! You do NOT want to roll the car backwards while in gear with the tensioner loose. This will retract the tensioner with a possible result of the chain jumping a tooth. Won't be pretty if this happens.

WopJob

· #6 · Aug 31, 2007

I was going to follow this procedure to tension mine without getting the cover off. Please let me know if it's wrong.

Park car on top of slighly inclined driveway, pointing down hill. Remove spark plugs. loosen tensioner bolt(1) 1 turn. Put car in 5th and slowly roll down a few feet. tighten tensioner.

(1)although my car is an 87 it has an 89 engine upon preliminary check I see that there is no tensioner bolt but an Allen socket. Am I looking at the right thing?

Also, I think that car should roll about 2 cycles of the engine correct?

Andrew

· #7 · Aug 31, 2007

I personally would not do it withouth removing the cam cover. But if I did, I would just rock the car gently forward only, a small amount, then tighten the bolt.

Andrew

john.harrill

· #8 · Aug 31, 2007

I know on the older engines you can adjust the tensioner with the car at idle.
Loosen the bolt about a half a turn with the engine fully warmed.
Careful of the fan!

Once the rattle quiets down, re-tighten the bolt.

Andrew

· #9 · Aug 31, 2007

No, no, no as to adjusting the chain with the engine running. This was in the old shop manuals but it's a bad idea.

Andrew

crashmctavish

· #10 · Aug 31, 2007

On a slope with the plugs out! It will roll away!!!!!!

WopJob

· #11 · Aug 31, 2007

crashmctavish said:
On a slope with the plugs out! It will roll away!!!!!!

I have a "brick" that I put under the car about 2 feet away. The slope is very gentle, ulmost imperceptable.

Additional reason for the plugs being out is that I want to look at the valve edge arounf the area of the plug for other reasons.

Bill

· #12 · Aug 31, 2007

papajam said:
Andrew is absolutely correct here! You do NOT want to roll the car backwards while in gear with the tensioner loose. This will retract the tensioner with a possible result of the chain jumping a tooth. Won't be pretty if this happens.

I can verify the "not Pretty" part. Did this the first time I adjusted the tensioner and it took me over 2 hours to figure out what happened and to fix it. Go forward only.
Its easy if you follow the correct procedures...

ghnl

· #13 · Aug 31, 2007

WopJob said:
...upon preliminary check I see that there is no tensioner bolt but an Allen socket. Am I looking at the right thing?

I suppose it is possible someone replaced the tensioner lock bolt with an allen head bolt but I hope not... The correct bolt has a small nipple on the end that engages a hole in the wedge shaped lock plate on the tensioner assembly.

Repeating the caution: do not remove the lock bolt. Merely loosen it 1/2 to 1 turn at the most (so that the nipple does not dis-engage from the lock wedge).

Sketch shown here: tensioner lock bolt

papajam

· #14 · Aug 31, 2007

...and pics of the lockbolt and the hole in the wedge into which the lockbolt fits.

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Silver78

Discussion Starter · #15 · Sep 1, 2007

Thanks for all the great feedback. I'll be doing this in the morning. I like to take the safe approach, so I'll adjust this as prescribed with the enigine off, with the cam cover off, 1/2 turn to loosen the bolt, a gentle push forward to take up the slack, and a screwdriver if needed to hold the tension while I tighten the bolt.

As I'm sure you could tell by my limited posts, I'm new to the forum, but have found it to be just terrific! I replaced my brake booster and master cylinder last weekend and it help a lot to go back and search the threads on the boosters. After reading the manual descriping to "remove the four booster nuts from under the dash", I just laughed. There was no way that was going to happen. I was thinking of taking the pedal box loose to access the nuts but wasn't sure if that was smart. I stopped what I was doing, came in the house, logged on and found several threads stating to do just that...to pull the pedal box. It made the job so much easier. Not sure what I would do without this wealth of information!

Again, thanks for the help!
Gary

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ghnl

· #16 · Sep 1, 2007

Use the screwdriver not just to 'hold tension' but to pry the tensioner out a bit. Often the spring behind the tensioner isn't strong enough to overcome any reluctance of the tensioner to actually move.

While you have the cam cover off it would be an ideal time to check cam timing and valve clearances.

With the #1 piston at TDC on compression (the #1 intake cam lobes will be pointing away from each other - i.e. intake points right, exhaust points left) a small mark on the camshaft should align with a mark on the forwards cam journal (cap). See sketch below.

Use a feeler guage to 'feel' the clearances between the camshaft and the valve's 'bucket'. Whenever a lobe is pointing away from a valve, slide various thicknesses of feeler gauges in the space. You'll have to rotate the engine around to check them all.

Actually 'adjusting' the clearance is a bit more work - you need to get the camshaft out of the way and swap a different size shim under the bucket to make the clearance more or less. But checking them is a fairly easy job.

BTW, you may need a new cam cover gasket. If the old one stays together you may be OK re-using it. Or not...

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alfaloco

· #17 · Sep 1, 2007

If you watch what happens during the tensioning process with the timing chain, sprockets and tensioner, it's easy to see that allowing the car to rock backward can actually depress the tensioner back into the plunger hole, just the opposite of what we want, right? So these guys are right- do NOT allow the car to roll backwards in gear with the tensioner loose.

The procedure that I like to use involves pulling the plugs, so I can get one good smooth roll forward about 10 feet in 3rd or 4th gear, so the engine completes more than one revolution. In this way, you're not fighting compression "bounce".

IIRC, the late and truly great Pat Braden liked to use a long screwdriver to lever the tensioner outward, not relying solely on the spring. I suppose there's pros and cons to this, but I don't like the idea of maybe overstressing the tensioner sprocket bearing by doing this. If I see the tensioner move outward like it should, then I'll rely on the spring pressure Alfa engineers provided.

Make certain the lock bolt illustrated is tightened securely. Again, these guys are right, don't loosen it more than 1 to 1-1/2 turns.

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john.harrill

· #18 · Sep 1, 2007

Andrew said:
No, no, no as to adjusting the chain with the engine running. This was in the old shop manuals but it's a bad idea.

Andrew

True; For the newer cars, the manuals don't use the technique. However the Giulietta manual does and I have used it through the years (30) with good results. You just have to exercise caution. Perform only at idle, loosen slowly, then tighten slowly.

Stan Murray

· #19 · Sep 1, 2007

So using a pry bar, don't you think you can over tighten the chain causing wear on the chain, the lower sprocket bearing and the lower chain?
The spring tention should snap the adjusting sprocket to a pretty tight chain tention. (that is if the spring is good and the adjuster moves freely)
TOO TIGHT is Bad.. There should be no sway in the upper chain across the two cams and there should be no sway or slack in the section coming up on the drivers side of the engine. The tentioner takes the slack out of the
passengers side of the engine only. So the reason for turning the engine is to even out the tenion. TOO TIGHT IS NOT GOOD!
Like everything else It is good to understand the chain function and it's relation to all related moving parts.
Just saying be smart.
Stan

Andrew

· #20 · Sep 1, 2007

I use very mild pressure on the pry bar, mainly just to make sure the tensioner stays at its own max travel while locking.

I used the idle-method on a friend's Duetto 20 years ago, and the rattling from the chain wearing against the cam cover made me jump out of my skin. I personally will never do that again. I'm lucky it didn't jump time, at which point I would have owed my friend a new engine.

Andrew

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