Technical Timing belt

[Dzso]

Hi there!

I need to change the timing belt (and everything) do somebody know how many tooth belt I need for the punto 75(176a8000)? Actually I ordered a set with water pump etc. in the set I have 129 tooth.

 

[portland_bill]

My experience of the FIRE engine, is that the tooth number also went with the tooth profile, changing from the original 'square' tooth, to the later 'round' tooth. That change occurred later than the Mk1 Punto I believe, so I'm surprised that there is a choice. Could just be poor listing by the supplier.

Rather than use any info from other people, just check you own car. Remove the belt covers and compare the tooth shape to the new one, without getting the new one dirty.
Mark the belt with chalk, and count the teeth. If you need to rotate the engine, add interim marks at 10/20/25 teeth or whatever is convenient. The outer face of the belt is sometimes marked with detail including tooth number, but this is probably worn off from its years of runnign against the tensioner.

 

[Dzso]

My experience of the FIRE engine, is that the tooth number also went with the tooth profile, changing from the original 'square' tooth, to the later 'round' tooth. That change occurred later than the Mk1 Punto I believe, so I'm surprised that there is a choice. Could just be poor listing by the supplier.

Rather than use any info from other people, just check you own car. Remove the belt covers and compare the tooth shape to the new one, without getting the new one dirty.
Mark the belt with chalk, and count the teeth. If you need to rotate the engine, add interim marks at 10/20/25 teeth or whatever is convenient. The outer face of the belt is sometimes marked with detail including tooth number, but this is probably worn off from its years of runnign against the tensioner.

Actually I have two options what I can order 108 and 129 tooth profile. The length same….
What I see on the two belts is the length is smaller between two teeth.

 

[Dzso]

What happens if I put 129 tooth instead of 108? The belt length is same. Does it work?

 

[portland_bill]

What happens if I put 129 tooth instead of 108? The belt length is same. Does it work?

If the length is the same, the teeth will be a different size, so will not mate with the pulleys. Early belts had a 'square' shaped tooth, so were longer, the later belt has round profile teeth, so shorter, and more of them.
As I said before, instead of continually asking the same question on here, go have a look at your car, as the answer is there. Remove the covers, look at the teeth, and if necessary , count them.

Edit: Just looked at the Shop4parts website (https://www.shop4parts.co.uk/?name=...=Fiat_Punto_(1993_to_1999)_1.2_8v_Timing_Belt). They describe the two belts as having either 9.25mm pitch, or 8mm pitch. So get the cover off and measure yours.

 

[Dzso]

Actually the head gasket is already sent. Everything is in my hands. I see the profile. I counted. I’m just trying to understand why?

 

[portland_bill]

Actually the head gasket is already sent. Everything is in my hands. I see the profile. I counted. I’m just trying to understand why?

The teeth on the belt do not actually drive the pulleys. The belt tension drives the pulleys, the teeth are just there to maintain the timing. Early belts, on all vehicles had the square teeth, as that was the original design. Later, having experimented with various tooth profiles, the manufacturers, led by Gates I believe, decided that the round profile was better, and most manufacturers changed to that profile.

An overtensioned belt will tear its teeth off. The belt will stretch a little between the pulleys, and the teeth are forced closer as they roll onto the next pulley, tearing them from their leading edge.
An undertensioned belt will also tear its teeth off, but this time from their trailing edge, as the teeth are used to pull the pulleys.
Failed belts are rarely the result of a defect, as manufacturing processes are very strict. They are made on a wide drum, then sliced off to the desired width. This also means that if there was a defect, the whole set would fail.

 

[blu73]

I've had a few P75 engines and confirm there is 2 belt types...

The 108 tooth belt is upto engine number 9042883, after that its the 129 tooth belt.

engine number is on the flat upward facing bit above the waterpump. But as said previously in the post, the easiest way to check is to look at the belt on the car.. the 108 tooth has the trapezoidal (square cornered) teeth and the 129 the rounded teeth. Or just count the teeth..

 

[Dzso]

I've had a few P75 engines and confirm there is 2 belt types...

The 108 tooth belt is upto engine number 9042883, after that its the 129 tooth belt.

engine number is on the flat upward facing bit above the waterpump. But as said previously in the post, the easiest way to check is to look at the belt on the car.. the 108 tooth has the trapezoidal (square cornered) teeth and the 129 the rounded teeth. Or just count the teeth..

I counted them, it’s 108 teeth. I made a mistake when I ordered the set because I didn’t see the two different types and I ordered a set with 129 teeth. I will need another belt

 

[portland_bill]

I counted them, it’s 108 teeth. I made a mistake when I ordered the set because I didn’t see the two different types and I ordered a set with 129 teeth. I will need another belt

You'll need to swap the whole set. The water pump is driven by the belt, so has a different pulley for the different belt. Tensioner might also be different.

 

[Dzso]

You'll need to swap the whole set. The water pump is driven by the belt, so has a different pulley for the different belt. Tensioner might also be different.

Yes, Thank you i see the difference. Next thing is the v belt…I have a lot of choice I will measure with a yarn or something.