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MG MGF Technical - Camshaft Belts

The cam belt for the engines fitted with the auto tensioner is longer by 2 teeth and 3mm wider AFAIK (145 teeth and 26mm wide as opposed to 143 teeth and 23mm wide). My query is this: provided that the correct tension can be generated with the manual tensioner (which it can), is there any technical reason that the longer belt cannot be used in the manual tension situation. It is wider (and is OK on the pulleys) and hence less stressed for a given load. Thus for higher lift cams with more load on the belt it should be better than the short narrow belt. Clearly on the auto tensioner engines one cannot use the short belt (I presume it needs to be the long belt to fit the tensioner) but that is not my concern. Yes, the longer belt will bend slightly more around the manual tensioner but not significantly. I can see no reason to not use the longer belt on the manual tensioner. Comments from my learned friends...............



Regards.....David
d mottram

I beleive that the cambelts that piper suppy with their warmer cams are wider than standard.
Steve Ratledge

David,

Officially as per the MGF manual:

"NOTE: Two types of timing belt tensioner
are fitted, type A is a manual tensioner,
type B is an automatic tensioner. The
tensioners and their timing belts are not
interchangeable."

However, IMO, as long as the number of teeth are the same (in a clockwise direction) from the two camshaft sprockets to the crankshaft pully and to the crankshaft timing gear, then I would guess it should be OK.
The extra length that the belt is (by 2 teeth) must be taken up by the longer distance that that manual tensioner will adjust to. This is provided that the tensioner will infact be able to have that extra travell to take up the slack of the extra length.

As you said, the angle of the belt to the tensioner will be slightly more more accute. Will this cause the belt to wear more quickly? I'm not sure.
The width of the belt may be important because once the belt is on and tensioned, and the engine is warmed up, the belt will "center" itself on all the travell paths. ie camshaft sprockets, crankshaft pully, crankshaft timing gear and tensioner.

The question is, are you willing to risk it?

cheers,
Branko.

Branko

David,

Some info for you regarding Dayco Belts.
The Dayco belt has 2 versions for the MGF 1.8i (Ref under Rover in catalogue)

Year: >08/1998
Ref num: 94371
O.E.: ROVER GROUP CDU2749
Dimension: 143 x 230H (143teeth and 23mm High)
Profile: SHP+
Barcode: 8021787519785

and

Year: 09/1998>
Ref num: 94906
O.E.: ROVER GROUP LHN100560
Dimension: 145 x 260H (145teeth and 26mm High)
Profile: SHP+
Barcode: 8021787535563

Cheers,
Branko.
Branko

Hi all,

and then there is of course the re-inforced "normal" Piper belt that has the same dimensions as the original old one for manual tensioner.
Fitted that one a few weeks ago on my VVC.
Comparing it to the original item there IS a diff. in "quality feel" as well as type of reinforcement fibres. / Carl.
Carl

I had this type of an experience with an old BMW 520 I owned, which had 1 tooth too many ! in fact I bought the car with the cam belt visibly loose !!

So I went to BMW and bought a new belt and a new tensioner...guess what!!
they were exactly the same as what was found to be too long!
SO
Through the subtle adaption of the cam belt tensioner it was possible to run the engine with the longer belt to a degree of engineering security, although I would rather have just been supplied the correct shorter belt (now unobtainable!)

Make sure that you fit the right belt before running the engine!!

Or you will be looking at a horrific bill for a new engine!!

Neil

I'd definitely go for the manual tensioner in preference to the automatic one - especially on an engine that sees plenty of high rpm.

The question is "is it safe to run the larger, automatic tensioner belt with a manual tensioner" - too which I'd pose, annoyingly, another question: "why would you want to?"

I guess you're after a more reliable timing belt, but is this belt the way forward, or would obtaining a timing belt from, say Piper, be more what you're looking for?
Rob Bell

A Piper belt sounds like the go after the assembled wisdom has been digested. Thanks to all for the input.

David
d mottram

David,depending on the year of the car the wider belt cannot be fitted to some of the earlier engines as the crank drive gear is narrower, you would have to change the bottom pulley and crank gear (from a later engine) to fit the wider belt as used on the VVC engines or from Piper.HTH.
Mike.
mike

Thanks for that Mike
d mottram

This thread was discussed between 16/03/2005 and 18/03/2005

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