Reporting Back on Results of Timing Belt Replacement

LarryC

LarryC

Curator of #10105275
Thanks to JimD I was encouraged that I remembered all about timing belts and my learning experience in this case was replacement of the tensioner bearing. All went mostly well.

On the tensioner bearing the main surprise is that it is tight on the pivot assembly. A ½ socket extension used as a large punch and a couple of wacks with a hammer with the assembly held in the hand, and the old bearing was off. A long bolt and a couple of washers worked well to press the new bearing on the shaft at its hub. A little antifreeze dribbled during the operation. I still am fuzzy on what the heck antifreeze is doing dribbling out just because I took the nut off that secures the tensioner bearing. But it stopped when the new bearing got its final seating after the ½ rotation of the crank and re-tighten routine.

Literally the second biggest delay/fight was getting the crank to AC compressor belt on (new one) as usual.

The biggest delay was that stinkin’ auxiliary cog. The manuals are all “don’t worry if that auxiliary shaft moves, just keep your eyes on the camshaft cog". Then the manuals fail to mention that, by the way, if that auxiliary moves your timing is shot because, oh did we mention, that auxiliary shaft runs the distributor. I could have used that reminder.

So I got a no fire situation on attempting to start. O.K., I then put the timing marks, crank and flywheel, on TDC, and, after remembering that the distributor shaft is splined (not slotted like some American vehicles), so there is lots of options for where to point the distributor rotor, I re-pointed the rotor to the No. 1 plug wire location in the cap. Re-assembled (after suitable cleaning and restoration of the distributor of course). No fire. Clearly with a 50-50 chance of getting no 1 versus no. 4, I got no. 4. Aligned the crank to TDC, rotated the distributor shaft 180, and finally got going.

Finally, I should mention that while changing the timing belt I immediately noticed that the camshaft cog was late by two cog teeth! Moral of the story: If anyone other than yourself did your last timing belt replacement, as in my case, you will want to do the belt yourself at the earliest opportunity. Fixing that little issue removed a mysterious idle-speed high frequency judder in the engine. Ran fine otherwise.

And finally, the raspy tensioner bearing is now gone and the engine is now louder than the bearing again, and in the process I fixed a couple things.

Next up: valve clearances, after I find a source for the legendary cam tool. Then on to replacement of the parking brake cables.
 
Congrats Larry

LarryC said:
The biggest delay was that stinkin’ auxiliary cog. The manuals are all “don’t worry if that auxiliary shaft moves, just keep your eyes on the camshaft cog". Then the manuals fail to mention that, by the way, if that auxiliary moves your timing is shot because, oh did we mention, that auxiliary shaft runs the distributor. I could have used that reminder.
Click to expand...


BTW... I did remind you about the aux in my laundry list of schtuff, because I got smoked by that d*mn aux pulley... twice. ;)

Step 13... second bullet item

13. Carefully replace the t-belt, again with care towards not moving any pulleys.

* Start with the belt around only the crank pulley and seat it into the teeth.
* Next put the belt onto the aux pulley keeping tension between it and the crank while engaging the teeth. Watch the rotor to be sure it does not stray, it is driven by the aux. You can rotate the aux prior engaging the new t-belt to realign the rotor if necessary
* Now take the belt over the cam pulley, again keeping tension from the crank to the aux to the cam. All slack should be on the tensioner side.
* Pull back on the tensioner spring with the vice grips and carefully slip the belt into position without disturbing the belt's teeth in the cam, aux and crank pulleys. Gently let the tensioner spring take up the slack.
Click to expand...
 
JimD, what can I say? I had a brain fade.

I think I read too many manuals and the info got lost.:blackeye:
 
Actually...

LarryC said:
I think I read too many manuals and the info got lost.:blackeye:
Click to expand...

As I was writing that list I kept thinking it was too long... might as well be reading the manual. It could probably be condensed significantly by someone less wordy than myself. Shorter would be better when you are standing over the car scratching your head. :)
 
Well... I was gonna add that...

... SOME cars, way back when this was possiby written... had the dizzy driven off the end of the camshaft, and NOT the aux pulley.

In any case... when I did mine 1000 years ago... I had he dizzy cap off and noted where the rotor was pointing... and when I reinstalled the cam belt... I made sure the rotor lined up where it was.

Fired right off the first turn of the key... didn't even bother to hook up a timing light.

Lastly... you say the cam gear was off by two cogs? If I remember correctly that would be something like 12 degrees... I believe the REASON people go to adjustable pulleys for racing is because even ONE cog tooth off is too much in order for the engine to run efficiently. Hmmmm... That would be really something especially since you are able to pass smog and all. Maybe I have this all wrong though.

Anyway... it sounds like you had the normal frustrations otherwise. Congrats in overcoming them!
 
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Yes, Tony you're right. Two cog teeth seemed excessive to me.

But neither of the timing marks on the cam sprocket were lined up as per the illustrations in the shop manuals. Another mystery that bears further checking. I suspect that I will be back with additional comment once I see how things work on some trial runs.
 
You aren't alone in your confusion over the aux pulley. I changed my belt a couple of weeks ago and had exactly the same problem. But a non-Fiat buddy of mine kept yakking about pointing the rotor at the # 1 cylinder. It took some time to sink in and when I consulted the Wiki, or thread, or whatever, I realized what I had done and that the rotor needed to be pointing at # 4. Instead of taking the dist. out, though, I just jumped teeth on the aux pulley until the rotor was in the right position. Fired right up. I think the timing is off, though because the engine is running much cooler than before and the exhaust smells mighty "gassy". Maybe it's too rich?
 
Drain coolant.

Quote: "A little antifreeze dribbled during the operation. I still am fuzzy on what the heck antifreeze is doing dribbling out just because I took the nut off that secures the tensioner bearing. But it stopped when the new bearing got its final seating after the ½ rotation of the crank and re-tighten routine. "

What you should be aware of here is that there is a metal end plate on the water jacket of the block held on by 5 bolts and a stud that goes through the center of the tensioner bearing. Removing the nut or tension allows coolant to pass along the stud into the centre of the Tensioner assembly. The tensioner bearing is a split 2 part double race bearing. The problem arises when the timing belt is changed and the coolant is not drained. The centre of the tensioner bearing gets filled with antifreeze and seeps into the tensioner bearing causing failure. As a precaution draining the coolant is a wise place to start before changing the timing belt. It is also a real pain with shaved head and cam box when you want to advance a tooth with out an adjustable cam box pulley. As you know beeding all of the air out of an X takes more than 1 or two tries over a few or so days and draining the coolant just to advance the camshaft a tooth at times seems hardly worth it.

TonyK.

Grimsby Ontario Canada.
 
TonyK, Thanks for the explanation.

I believe that I am o.k. as only a small seepage occurred during the operation and things were pretty dry by the time I reassembled the bearing. But that makes sense about the water jacket end plate. It's a pity that the manuals never really address this. One wonders what else is missing from the manuals.
Speaking of which...After a good run I can report that the bearing is now very quiet. Unfortunately the X accelerates now like poop. Timing is spot on with a timing light. Vacuum advance is working well. But acceleration is very poor and a quick punch of the throttle in gear delivers a very real bog. I have a feeling that this cam sprocket timing mark issue is going to grow into another thread that will reveal something alarmingly new to us (or me at least).
But due to professional matters it will be a few months before I can replicate my efforts of the past weekend. So in the mean time, let the theories begin!
 
Cam timing.

You have to tell us what camshaft is in your car. I have seen a stock X 78 still run with 4 teeth displaced.

You may have to check the camshaft timing off of the bell housing and with a feeler guage off of #4 cylinder if it is an unknown camshaft.

I have a 40-80 camshaft in my car currently and at the advice of Matt Brannon advanced it 1 tooth because I shaved the head .120" and the cam box .040". The result is significant, however this changed my Megasquirt Tuning and VE tables had to be adjusted quite a bit. That's another story.

Get back to us with some more information.

TonyK.

Grimsby Ontario Canada.
 
Thanks TonyK. More or less where my thoughts are going.

It is beginning to look like what we need is a real world set of instructions for the timing belt replacement that ignores the alignment marks on the cam sprocket and goes into the details on how to determine where the cam sprocket should be, just in case there has been some head shaving, cam changes, or the like along the way.

But here’s the rub with the non-stock cam theory: This X has not been out of my sight since new, I did not change the cam, nor did I ask anyone to change the cam. So the natural assumption is that it has the stock cam. If it does not, then that would be scary. In fact, that is why I am so hard over about people doing mods. Mods tend not to be recorded for the next owner. But it may be that even that is no guarantee.

I may not have time for a while to do the checks I need to do, but pointers are definitely welcome.
 
Well then

That makes 2 of us because I purchased my X in January of 1979 and it didn't leave the dealer ship with the stock cam or carb. Now you say the car runs like poop, that just about describes why I changed the cam and carb with only 50 KM on the car. I will guess then that the cam pulley is stock as well.

The 35-75 cam that I purchased from Al Contentino at Faza was out by about 8 degrees from the stock marks on the 79 metal cam pully. From the Faza catalog you remove the spark plugs and put #4 piston at TDC. Check the mark on the flywheel, then remove the cam box cover and use a .002" feeler on #4 intake valve turn the engine backward 10 degrees and mark the flywheel with a dab of nail polish repeat and continue to check when the feeler gauge touches the valve shim. You will know if you are out. ( 35-75-75-35) If your camshaft is stock 10-54-54-10 then the lobe will be touching in less than 10 degrees of crank rotation. ( The fly wheel end has in the bell housing 0, 5 & 10 degree marks.) If it isn't then the marks are out on the pulley and you will have to paint new marks on it and slip the belt another tooth or what is required to time it correctly.

Years ago when I didn't have any money and tools were expensive I would just make a degree wheel from a sheet of aluminium cut in a circle and use a carbide scriber and a protractor to lay out the marks on the aluminium plate. I would cut the centre out of the alum. plate and tape it to the cranke pulley after I removed the Right rear tire and plastic guarding. Then with #4 cylinder measure when the intake and exhaust valves open and closed to obtain the camshaft timing. Crude, but very close.

Give these ideas some thought.

TonyK.

Grimsby Ontario Canada.
 
The IMPORTANT question is: What shade of nail polish...

... do you recommend?

HAHAHAHA!

My wife actually caught me stealing hers one day and REFUSED to allow me to use it on my timing marks!

HA... I guess I'm just not MAN ENOUGH to go purchase my own... Not like you!

BTW... Testor's makes PAINT PENS for model building and the like... they work just as well, I think... but ya gotta be over 18 to buy them, same for the glue!
 
Well that explains the coolant drip...

This is my third timing belt R&R and I don't remember that from the first two, but sure enough I have a small drip in that area with the t-belt and bearing off right now. I drained the coolant since I'm replacing hoses, water pump and v-belt right now anyway. And yes, I got burned on not marking the aux shaft too! Oh well, I got a 50-50 chance of setting it back correctly (cyl #1 or #4).

Brian
 
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