BC

I didn't take any pics of the worn gears, but the pictures others have posted is representative. Worn gear face, slight bowing in the center from belt tension being too high or whatever the reason.

So this is intended to help a worn one be used. If we all had the $$ it wouldn't be on the table as an idea right? I have enough gears for three engines and they are all new or NOS.

This is for a different reason, and and if it proves effective, I'll continue to do it.

I sand blast the gear, but before that I take a sheet of thick steel and cover it with sand paper, and slide the gear along that surface. It corrects any imperfections from the wear and after the sand blasting it basically looks like new. I then coat it with this material and bake it on.

This is not tested. It is not suggested. I am building a cheap high compression motor to prove/test some of my theories. I will be using a Porken tensioner to even out the tension these see.

snoz

I purchased a new set but will be watching this thread to see how things go. Very interesting.

BC

These won't see the racing belt I think. The stretch is no issue for me at this time. Whether the motor stays together is a main concern.

Tails

The cam sprocket looks good.

I have been doing the same using ceracote micro-slick with with a pencil hardness of 6h, scratch hardness of hb. The ceramic coating is air dried, however I have been informed ceracote make an oven dried coating as well.

What is the hardness factor of the final coating you used?

I recently removed the TB covers and inspected the sprockets on my 928 and the coating has worn through only on the top of the sprocket teeth on the RHS sprocket, (looking from the front of the engine) while the coating within the teeth profile is in good condition. The LHS sprocket coating is in good condition. The sprocket only are only under load within the HDT profile.

I determined that the installed sprockets were fit for further use until the next timing belt change.

I have had two sets of camshaft sprockets coated and one lub oil pump gear, however I'm not really satisfied with the blasting and clean up prior to coating. I was my intention to install the best set this time together with a new gates belt to gauge the wear rate etc. In view of my finding above this has currently been shelved.

I currently have another set of curvilinear high torque drive profile sprockets which I will have done using a local agent for Ceracote. I will determine what coating to use after I have cleaned up the gears, checked the outside diameter for roundness, machined out the slight wear on the top of the teeth and spoken with the application agent.

Keep up the good work and please keep us informed.

Rob Edwards

Tails-

Inquiring minds wanna know: How many miles on your coated gears since installation? Was there any appreciable wear on the tooth profiles when you had them coated?

There's the obvious chicken and egg question of whether any 'premature' wear of the cerakote coating is due to dimensional changes in the used gear that gets coated, the prep process for coating, or inherent wear rates of the coated layer.

BC

Clearly you are much more exact than I.

I do not know the hardness, but one point I wanted to focus on was your comment about grinding the outside of the gear - thats basically what I was describing in my posts about sanding the outer most part of the gear tooth, since that is where most of the wear is. If this were really okay, then alot of gears would continue to be usable once a bit worn right there. There is little or no wear on the sides of the valleys and the bottom of the valley.

The stuff I used is on this page:

http://www.techlinecoatings.com/hi-p...-coatings.html

DFL-1

I supposed I could have used the TLML. But I don't see that in their online store. Probably because its solvent based.

Hilton

I've got a bead blasting cabinet if you want a lower risk alternative to the guy who screwed up the last set of gears.

You're welcome to drop round sometime late next week - I need to organise the garage a bit to make more space for working on 928's again after a hiatus, so something which forces me to tidy up in there beforehand is welcome.

BC

I learned that the lower Psi on the media blast is better, but takes more time.

FiveElements

sounds good to me. What coating should we ask for from TechLine? Is there more than one option?

BC

I used DFL-1 but I have not yet installed them. Hoping for next weekend.

Rob Edwards

Updates on DFL-1 coated gears with XX,XXX miles on them?

BC

We can check when you come down to help me on the white car. We can take off a cover and take some pics.

AO

~40k miles on recoated gears in this post...

https://rennlist.com/forums/928-foru...l#post11023681

BC

I sure hope the hell they look better than that.

AO

They felt and looked great. There was no issue with them . The coating did it's job.