If anyone has a new timing belt can you please measure the hight of the semi-circular lobes from the inside flat section of the timing belt to the peak of the lobes.

The heights of different belt manufactures lobes would be a great help also.

I am currently investigating the different depths of the semi-circular teeth on the camshaft drive gears, the lub oil pump drive gear and the crankshaft drive gear, as I have gears that have wear on the outside diameter of the flat sections of the semi-circular teeth and I have measured different teeth depth on the gears mentioned above..

Thanks in advance for the help.

 

Can anyone help?
Thanks.

 

I have a new Gates belt in the shop......brb.

 

I think I have a new factory belt in the garage. Will report back later.

 

I measured a few belts
New Gates tensioned on the engine
5.60 MM total thickness
2.20 MM in the groove

3.40 MM tooth ht

Used Gates with 15 K miles off the engine
5.68 MM total thickness
2.36 MM in the groove

3.32 MM tooth ht

Used Uniroyal off the engine
5.50 MM total thickness
2.36 MM in the groove

3.14 MM tooth ht

 

new Gates off engine 5.9mm total, tooth 3.2mm

used belt off engine 5.8mm total (mileage and make unknown)

 

Thanks Malcolm, Rob and Stan.

I will advise when I have completed my research.

Also thanks to Hilton Day who has kindly given me numerous used gears/sprockets

 

If you want some more gears let me know.......just finished tbelt project on GTS

 

Thanks Malcolm,

I will see how I go with the ones I have got at the moment, however I will get back to you if I need more.

Regards,

 

I have a new one, genuine nos , branded HTD something, Porsche.
I make it 6mm overall, 2.8mm base, giving a 3.2mm tooth height.
jp 83 Euro S AT 55k

 

Thanks John.

Hope all goes well with the White Wonder.

Best regards,
Alan

 

I have just posted the following message on a post titled Momgo's "First Time" - Timing Belt/Water Pump thread, as he is looking at the possibility of coating his aluminium camshaft driven sprockets.

This is a brief update on where I up to:

Currently in the process of having camshaft sprockets, lub oil sprocket and crankshaft drive sprocket for the the S4, coated with Cerakote Microslik C-110 ambient-cure ceramic dry film lubricant which is a division of NIC Industries Inc.

Address NIC Industries Inc
7050 Sixth Street
White City OR 97503

Phone: 541-826-1922
Fax: 541-826-6372
Web: www.nicindustries.com

They also have Creakote Microslik P-109, which is a baked on ceramic.

As per my previous recent thread on this subject, I advise that I'm currently undertaking a study/investigation on the timing belts' sprocket and belt geometry of the camshaft drive and driven sprockets, to ascertain what condition the camshaft sprockets need to be in to be suitable for refurbishment. This study will also try and ascertain the maximum wear limits of the sprockets and the clearances between belt lobes and sprockets.

I will also investigate whether the whole of the sprocket needs to be medium blasted or just the sprocket tooth area, thereby saving money.

I have actually seen camshaft driven sprockets that has been nearly completely worn down to slight "bumps" and the engine was still being operated. Unfortunately I do not have photographs of these sprockets.

The camshaft sprockets and belts are 8mm Synchronous Curilinear tooth HDT belt profile for the later MY 928s , whereas the older model 928s had Trapezoidal belt profiles.

At the completion of my investigation/study it is my intention to write up a full specification on how to prepare and coat the sprockets to be handed to the contractor for guidance (if required). from the surface preparation, racking, gas out, check list before spraying, spraying procedure and air drying or baking depending on what grade of Cerakote used and in addition some words on the belts geometry and the clearances between the sprockets and the belt lobes.

I would suggest that 928 owner don't choose any blasting and coating contractor. I will update my problem later in another post.

 

Tails - I've got a few brand-new cam gears on the shelf here too. Actually, thinking about it, I have brand-new of all the gears somewhere here..

I can bring them along to second-Tuesday on the 14th if you want to borrow them for measuring and comparing to the coated ones?

 

Tails, thanks for researching this this project.

I am wondering if it would be better to replace the crank drive gear with a fresh part,
instead of putting a slippery coating on this gear,
my concern would be that the slippery coating may cause the belt to slip off the gear should the belt have a loose fitting episode.
Of all the gears on the belt drive this one should not have a slippery surface IMHO,
infact you would want it to have some grip so the belt will not slip on the tooth flanks

Otherwise the recoated crank gear would make a nice paper weight for your desk.
Should you decide to not use it in your research

The oil pump gear has been superseded with a new steel gear and the rear 1mm shim should be removed before fitting the new steel gear

 

Hi Hilton,

I will bring along the gears that I have had done to compare with your new ones. Do you have a new belt as well, so we can look at the clearance between the belt lobes and the sprockets?

Hi Stan,
Thanks for your advice regarding the camshaft drive sprocket and also that the lub oil pump driven sprocket is now made of steel. Is the new lun oil pump sprocket coated with a ceramic coating?

If all alignment is correct there should not be any problems with the belt slipping off the camshaft drive sprocket. In some of the designs of these type of belts, the sprockets have flanges fitted to stop the belt migrating off the sprockets. These are usually fitted to extra ling indexing drive belts, not with automotive camshaft drive belts

It is imperative that the axial alignments of all sprockets, rollers etc., are in parallel and the vertical alignment is at right angle to the axial line and the sprockets and the rollers are in the same plane.

I have noted that some of the camshaft sprockets tops have worn and the wear indicates that they have been out of axial alignment, as seen by the differential of the depth of wear on the sprocket teeth tops..

When the sprockets have been renewed or refitted after refurbishment it is advisable to check the run out of the belt through the viewing holes in the camshaft covers as well. Any excess run out indicates out of alignment.

I believe that the re-tensioning of the belt after renewal is to allow for the wearing in of the belt and sprockets, which can cause loss of tension. I also fully subscribe that the belt tensioning should be carried out every 12 months to prevent “ratcheting of the belt” (climbing of the belt lobes up the sprocket teeth), which can occasion due to loss of tension. If the correct tension is not maintained it can cause failure of the belt or jumping of the teeth.

Regards,