Author Topic: Alfa busso alternate method cambelt change  (Read 1048 times)

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Alfa.mg

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Alfa busso alternate method cambelt change
« on: August 04, 2021, 01:04:21 PM »
Thought I'd throw this out there, curious to see what people think. I've just completed another cambelt change on the 2.5 v6 on my 156. I've got the skinned knuckles to prove it haha. 
This time around I did it without using the cam locks as alfa intended and I really feel it is so much easier. The alfa method of locking the cams requires you to disturb and pull apart quite a bit on top of the engine to uncover the cams. You also need a dial indicator to find TDC from memory, and worst of all, you have to undo the cams from their sprockets. Once you have undone these, the position between the cam and sprockets is infinitely variable, which makes it hard to do a gross error check. Last time we did this method, there was a tiny vibration in the revs and required re-doing. We put this down to the cam locks not being 100% perfect, they were aftermarket ones ordered online. No doubt an original alfa set would be better.

Our method (dads method), is to rotate engine to a point which you can feel cams are unloaded, (our position happened to be crank with key at 9 o'clock position) Mark with paint all cam gears, and crank position accurately. We then use generic cam locks on the cams, one between front bank and another on the back.remove belt and replace water pump idlers if need be. Then put new belt on cam gears working left to right, top to bottom. Uning a 19mm spanner the cams can be rocked a little to help get belt teeth on. The belt can be put on all the way onto cam sprockets. The crank sprocket slides off easily and the belt can then go on it, then slide whole sprocket with belt onto crank. Set tensioner and your done. Now I feel if my water pump went I could make the change without disturbing entire engine. But the best part is, it's much easier to tell if you have done it correctly as if you are out by a tooth, it is dead obvious and you will not be on the marks you created.

Thoughts? Or has everyone been doing it this way already? Has to be the only engine in the world without factory markings for position.
1983 alfasud TI 1.5 silver
1990 Alfa 33 cloverleaf 1.7 white
2001 Alfa 156 2.0 red
2003 Alfa 147 2.0 red
2001 Alfa 156 2.5 Monza silver (now)
1983 Alfa Sud TI 1.5 red (now)
1974 berlina 2000 white (1 too many)

bazzbazz

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Re: Alfa busso alternate method cambelt change
« Reply #1 on: August 04, 2021, 02:22:58 PM »
Sorry, but doing it this way puts the timing out.

I have many a time had to do a timing belt change on a V6 Busso where the previous individual/mechanic/specialist has done it with tippex markings and not using the correct cam locking tools, and every time the timing on the cams is out.
(Not once, not occasionally, but every time!)

It affects the inlet camshaft on the rear bank most, and there have been cases where the timing has been out so far I could not even get the cam lock 1/2 way onto the the corresponding cam, having to remove the belt and rotate the camshaft to get the cam lock on.

Trust me, if this method was in any way reliable I would adopt it, as it would save countless hours and my clients much of their hard earned money. (I make more money from my clients by saving them money, not costing them more.)

Unfortunately my training causes me to have a unavoidable compulsion to do things properly and correctly.

However if you are satisfied with the results and how the car is running then you should be happy.
« Last Edit: August 04, 2021, 02:31:33 PM by bazzbazz »
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bazzbazz

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Re: Alfa busso alternate method cambelt change
« Reply #2 on: August 04, 2021, 02:29:26 PM »
Has to be the only engine in the world without factory markings for position.

Sorry, but that's not correct and a big myth.

A/ Each Camshaft has timing markings on it for conformation of correct positioning
B/ The Crankshaft Accessory Belt Pulley (Harmonic Balancer) is marked to confirm correct positioning for TDC.
C/ The Flywheel is also marked to confirm exact TDC and can be viewed through the viewing port on the top of the bell housing (Manuals only)
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Alfa.mg

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Re: Alfa busso alternate method cambelt change
« Reply #3 on: August 04, 2021, 09:50:00 PM »
I just thought it would be an interesting conversation to have, and will not try to sway everyone as Im sure there will always be the opposing opinions on this.

I stand corrected on the timing markings, I did not look into them this time as I was hell bent on not taking off all the cam covers. Thanks BazzBazz.

While I'm sure our method can be done poorly, and its probably only the poorly done jobs that have to take it back to the pros, I also don’t understand how it is different to the official method on many other cars. Locking pins for crank and cams. Replace belt, tension, and remove pins. We have always done it this way and have never had an issue.

As a precaution, we always turn the engine by hand through a complete rotation in correct direction, back to starting point to make sure they still all line up. If we were a tooth out here, we would know.

Ill let you know if any of my valves hit a piston (just kidding!) but so far so good and the busso is sounding smooth as silk up to the redline ;) always a good feeling after a cambelt change, 5 years of driving pleasure before my knuckles get skinned again.
« Last Edit: August 04, 2021, 09:56:23 PM by Alfa.mg »
1983 alfasud TI 1.5 silver
1990 Alfa 33 cloverleaf 1.7 white
2001 Alfa 156 2.0 red
2003 Alfa 147 2.0 red
2001 Alfa 156 2.5 Monza silver (now)
1983 Alfa Sud TI 1.5 red (now)
1974 berlina 2000 white (1 too many)

bazzbazz

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Re: Alfa busso alternate method cambelt change
« Reply #4 on: August 04, 2021, 11:29:37 PM »
I just thought it would be an interesting conversation to have, and will not try to sway everyone as Im sure there will always be the opposing opinions on this.

Quite so, and I can assure you there will be as many for as those against.  :)

While I'm sure our method can be done poorly, and its probably only the poorly done jobs that have to take it back to the pros, I also don’t understand how it is different to the official method on many other cars. Locking pins for crank and cams. Replace belt, tension, and remove pins. We have always done it this way and have never had an issue.

I said it causes the timing to go out, I never said how much it causes it to go out. Sometimes it's little, sometimes a lot.  ;)

As a precaution, we always turn the engine by hand through a complete rotation in correct direction, back to starting point to make sure they still all line up. If we were a tooth out here, we would know.

Ahh, there's the rub, it's not a tooth out that's the issue, it's 1/3 of a tooth here, 1/4 of a tooth there, and of course, you're working on the principle that the timing is fully correct in the first place. Due to the usual wear and tear on belts and everything else in the mechanical train the timing can go out of alignment slightly, not always, but it does happen.

There are also many cars that don't need any adjusting and are pretty good as they are, like yours most likely is. However you could talk to many of my clients who thought their Busso's were running awesomely, then after having had the timing reset precisely thought differently.  :o

But most of all, take it for a drive, enjoy yourself and sit back with you're favorite tipple and bask in the joy of getting the job done.  8)
« Last Edit: August 04, 2021, 11:38:10 PM by bazzbazz »
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Ascari32

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Re: Alfa busso alternate method cambelt change
« Reply #5 on: August 16, 2021, 08:18:31 PM »
I own a 3.0 GTV, virtually from new. A 1998 with 30,000 miles. It has always been used for continental holidays, going home to see mama on several occasions. Always maintained by a specialist independent.

Previously, I owned an Alfetta GTV6, also virtually from new. Whilst I was really comfortable with changing belts on the Alfetta, also completely stripping, balancing and rebuilding with Colombo Bariani cams, my 916 has always been a lot more daunting prospect and hence I left it to experts.

But the Quad has been around for many years now and I do not understand why someone has not made some modification/designed an external cam - lock which eliminates the need to strip the covers off to fit them directly to the camshafts.

Surely it cannot be that difficult, the relationship between all four camshafts to the crankshaft is constant, never to be altered, unless tuners were deliberately wanting to modify it.

I may be barking up the wrong tree but, it is only these five element that need to be fixed with respect to one another. All else is superfluous surely?

The timing belt appears to be the real problem, but fitting adjustable sprockets can negate its influence entirely. All that is then required is to ensure the physical markings are in their correct positions “from the off”. So, if camshaft marking are aligned with a bearing cap, all that is required is to mimic those markings onto the hub/flange of the adjustable sprocket and “fix”/align that to an external timing mark engraved externally.

Or is that what they do already.

Either way, not doubting the expertise of those shops who are expert in the current process, it seems an incredible Faff, for what should be an easy task.