Hello thanks for reading, 

 

so I have recently bought two GT camshafts to go in my coupe s. I thought I was better off buying the two from different people so I could choose the best to use.   

 

Camshaft one,   Lobes look in great condition with minimal wear or marks. I can’t feel any surface marks, however the bearing faces have vertical scoring the worst of which is pictured. I can only just feel the worst one with my nail.

 

camshaft two,  err well the opposite 😖 smooth bearing surfaces no problems but the lobes have these dark patches on them. I can’t feel anything with my finger or nail but they look scary. 

 

Which should I use? Or am I better off scrapping them both and trying again.  Any advice would be great.  

Thanks!

The dark patches are on the face that exerts no force.

Probably been stored poorly, but looks like it's only surface corrosion of the nitriding.

 

Are the pointy lobe slopes unblemished?

 

I'd use the dark patches one first myself. Bet it'll be shiny in 100 miles.

Are you the changing hydro tappets?

 

The other has had dirty oil I reckon.

 

 

 

Thanks for the reply buddy,  there are some small patches on the pointy parts too.  There’s some patches on every face but yeh maybe it’s just moisture getting to it.   I’ve attached a photo of the worst lobe, what’d you recon? 

I’ve bought a brand new set of INA cam followers that I will be installing too. 

Nothing on the lobe slope, only some pitty wear on the tip.

But not awfully flattened visually.

 

This is a picture of the location and kind of damage that would be terminal

https://tribology-abc.com/poll/case07.htm

 

Use a micrometer to check lobes are same max distance?

 

I think 3F is 9.6mm valve lift (and 1mm valve opening at TDC), so compare max to the base circle (and make allowance for geometry of lifters - by rocker ratio, irrelevant for hydraulic tappets I think?)

https://www.polotreff.de/forum/t/217734?op=1

 

Check it (and the other cam) is straight (measure the run-out), by rotating mounted at either end

(laid in a v-cutout in wood distributor end with a drill chuck in a vice gripping threaded bar screwed in the pulley end

and rotate slowly looking at a fixed edge or felt tip pen clamped in a vise nearly touching, for example)

but ideally with a dial test indicator, at the central bearing and then each bearing in turn. 

 

Edited 4 March, 20206 yr by dvderlm
corrected 0.1 clearance to 1mm opening at tdc

i wouldnt be keen on either ...the lobes look a bit too far gone 

 

remember the cam bearings arent replacable if you choose to run it and ruins the bearings 

. Thanks for the advice, I’ll have a check on Monday when I’m back at work. We have a surface table and all the equipment you have mentioned.   I’m also going to have a think about buying a schrick 268 cam. However for a daily car and standard engine I feel this might be a bit aggressive and or valve problems with pistons. 

 

Thanks again 

plenty of people run the schrick 268...theres no valve to piston issues i have one myself 

Awesome, seems like I’m going along the lines of selling the two gt camshafts and buying the schrick/Newman.    How’s your honest opinion on the performance increase and drivability? 

havent really driven it enough to give much of a review , its one of the most popular ones with polo owners and a top brand so i went with that , newman can do one the same but you have to ask for it , its a bit cheaper 

Ok cheers for help!