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Discussion Starter #1
Milano/75 3.0 V6
New timing belt, with mechanical tensioner replacing hydraulic.
Belt is walking forwards on the pulleys until it touches the crank timing wheel and plastic belt cover.
Didn’t do it before, no other mechanical changes.
A bit of research points to too much tension on belt (I reduced tension, no change), or an alignment problem.
The new tensioner is flat against the block, and itself seems solid.
Only remaining suspect item is the oil pump/distributor drive pulley, which rocks just a fraction, but visibly, tho why this would be having an effect now, and not before, I don’t know.
I’ve not seen a diagram of these pulleys, Or where any bearing actually sits, to see how they are put together. Bearings or rebuild kits don’t seem to be listed by the usual suppliers....what’s the story with these?
Any pointers or suggestions welcomed.
And yes, I do need a comprehensive repair manual.
 

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Strange, the pulley guides should limit belt travel. Only one pulley needs to have these guides.

So don't understand the belt hitting the plastic cover. Are you sure the covers are on right?

But does sound like a pulley is not parallel
Pete
 

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Pulley not parallel will cause this. Did you change tensioner with the belt, or only the belt?
 

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Discussion Starter #4
Mark-toro - New mechanical tensioner installed at same time, replacing hydraulic.
PSK - I've read that guides are in place on many cars, Retro-fit kits available for some cars, and even Gates promotes their use to cure walking.
There are of course no guides on cams, tensioner (old or new) or dist drive pulleys.
Belt covers were on properly. Without them, the belt is definitely walking forwards until it Is restricted by the toothed crank timing wheel, which also suggests there are no guards around the crank belt drive cog , or they have been removed.

So - does the Busso have guides behind the crank pulley (Perhaps missing on my car...hard to see)?

Aside from any missing guides at the crank, thats 2 votes for a misaligned pulley...so I’d still be very pleased to discover more detail on what Is behind the dizzy pulley and what can be serviced/replaced.
 

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There has to be at least one pulley with guides, or maybe 2 pulleys with opposing guides. I am sure your engine did not leave the factory without guides

While I have done a 75v6 timing belt, I cannot remember, but I do remember that my Sud engine had guides on the crankshaft pulley ...
Pete
 

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Discussion Starter #6
I’m kinda with you Pete, you’d think there would be guides somewhere.
The crank pulley is the only area I can’t see, so I’m looking for some pics or parts diagram to see what I should have there...or not...before I go on, as well as the dizzy pulley details, if someone has that info.
Thanks for responding.
 

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You try doing a search? I know someone had the same problem on here a while back, but I do not recall the resolution.
 

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The distributor pulley only mounts one way n a locating pin. If it is mounted a hundred eighty degrees out, it won't bolt flush and will wobble. You might want to check this possibility out.
 

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There are guides on the crank pulley as PSk mentions. The distributor pulley should not wobble, but likely was in that state before the belt swap. The distributor pulley shaft rides in a bushing / bearing in the front wall of the head. You can remove the pulley from the front of the engine to service the seal, but I believe you have to pull the head to remove the shaft and access the bushing.

Because the issue appeared after the swap, I suspect that the new tensioner is causing the belt walk. Are you using the 164 design or the Tom Zat style fixed tensioner design? Sounds like you just converted from the oil fed version. I have never experienced issues with the 164 design in 200K miles of use. If you are using that style, I would look closely at the mounting surfaces of the block and tensioner. Especially consider the areas where you plugged the oil feed and return. Look for burrs - it won't take much.

If you are using a Zat style, then the issue may be in the tensioner itself. Perpendicularity of the shaft to the mounting surface is at issue here and welding of the Zat style mount always made me nervous. I understand the effects of weld pull from work. For that reason, I have never tried one myself. However, the mounting surface considerations described above would still be applicable.
 

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Hey Ranz
.
Only remaining suspect item is the oil pump/distributor drive pulley, which rocks just a fraction, but visibly, tho why this would be having an effect now, and not before, I don’t know.
That is the guilty party. I just worked on a GTV6 here in Houston that had a belt walking like the way you describe. We found the bolt holding the oil pump/distributor drive pulley to the shaft had loosened and let the pulley rock back and forth.

There can't be any play in that pulley.

Take out the bolt, inspect it for damage and also the threaded hole in the shaft. If they both check out replace the bolt and the washer and use Blue loctite.

Let us know how this works out.

Bye
 

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Discussion Starter #12
Righto,
Thank you all. That‘s a few things to check, I’ll get into it today.
Marktoro - 164style, I believe, not the Centerline-style item with bolt adjustment and locknut.Thank you for the comprehensive info. If there are indeed guides behind the crank pulley, is the front guide a separate item, which perhaps we may have bent, or is missing, or is the timing wheel itself the front guide?
(I'm just trying to figure if I’m looking at the complete picture or not When I stick my nose in there...)
 

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If there are indeed guides behind the crank pulley, is the front guide a separate item, which perhaps we may have bent, or is missing, or is the timing wheel itself the front guide?
There are no guides for the timing belt on the 12V Buso V6. The lower crank pulley has a slightly dished washer behind it. The purpose of the washer is to stop oil leaking from the front main seal getting onto the timing belt, and to protect the seal from debris thrown off by the timing belt. Iideally neither of these events would happen, the washer is there as a backup measure.

The back of the crank pulley is a flat surface and the timing belt should never come into contact with it.

The rest of the pulleys, the two camshaft pulleys, the oil pump pulley, the tensioner pulley are all smooth pulleys without lips or anything else that could be called a guide. The belt should run in the center of the camshaft pulleys, and unless one of the other pulleys is wobbly, or not parallel to the engine block surface it will.

Some newer engines have various kind of guides for the T belt, chiefly lips at the edge of the pulley but not the Busso.

Do you have the factory manual for this car? You need it. If you can't find it online I can email it to you. Contact me via the PM system.

Bye
 

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There are no guides for the timing belt on the 12V Buso V6. The lower crank pulley has a slightly dished washer behind it. The purpose of the washer is to stop oil leaking from the front main seal getting onto the timing belt, and to protect the seal from debris thrown off by the timing belt. Iideally neither of these events would happen, the washer is there as a backup measure.

The back of the crank pulley is a flat surface and the timing belt should never come into contact with it.
They are guides; and yes maybe the have multiple purposes, but if your crank seal is leaking, that washer will not stop the oil getting on your belt. It's primary purpose is a timing belt guide. And yes the back of the crank pulley has two functions too, timing belt guide and v belt drive.

All timing belted engines have guides, and a belt usually ends up running against one side. It is close to impossible to manufacture a belt that perfectly that it will run dead in the middle, so you need guides. Timing chains have guides too, the teeth of the pulleys act as a guide
Pete
 

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Discussion Starter #15
PM sent re your kind offer Milanoguy.
Thank you. I’ll look into this further when received.
 

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Ranz I have had similar problems and not just with Alfa. I have fixed this with a mixture of rotating engine by hand pushing the belt back. Changing the tension slightly. Repeat many times until the belt has appeared to settle in.
 

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Happened to find an almost useful photo that shows the inner timing belt guide with the front v belt pulley removed (the inner face of that would be the outer timing belt guide). Note they are pulling off the crankshaft timing belt pulley in this photo.

I know Ranz you find the cause and solve your belt wandering problem 👍, I'm just very nervous/worried regarding comments that these engines do not have timing belt guides, when they simply have to. I used to be an average design draughtsman in mechanical engineering, and you just would never design a belt drive system without a guide.
https://sdp-si.com/resources/beltdesignsuggestions.php said:
Because of a slight side thrust of synchronous belts in motion, at least one pulley in the drive must be flanged. When the center distance between the shafts is 8 or more times the diameter of the smaller pulley, or when the drive is operating on vertical shafts, both pulleys should be flanged.
Pete
 

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The crank shaft pulley is the front belt guide. I mean the big one. The harmonic balancer.

Edit :sorry Pete I just re read your post and I just repeated something you already said.

Mental note. Wake up before checking emails.
 

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We all suffer from that alfettaparts2 :)

Pete
 

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What brand belt was used in this situation? Maybe use another new belt.
 
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