Who's in for hardend camshafts?
I go a phone call today . All the cams are done . Thanks to everyone who sent cams in to get the cost down on the batch. They should be delivered friday. They said the lift on the exhaust cams will be right at .380". All used cams sent in were polished before sending to the heat treatment process. Ive have an engine ready to go for durability testing asap. Some of these projects are so draining. Its been a year for this .
-
cannondale27
- Posts: 0
- Joined: Wed Mar 10, 2021 10:41 pm
Well now that the nitriding seems to have worked on the cam lobes a side effect has been reported by Tim. The roller bearing surface of some of the cams he has run in his trail quad has fatiged and chewed up the bearing. He believes the process has softened the base metal and although the nitride coating easily can resist wear it needs the hardness underneath to handle the stress that the roller bearing is placing on it. The cams I have show no signs of fatigue but maybe they just need more time on them or the hardness is high enough on them. So I have decided to deal with this matter and have already built and am running a pressure fed cam bearing on one of my 460 engines to see how it will handle the load in case this is a wide spread issue . The other option is retreat the cams again to bring the rockwell up higher . The downside to that is I believe it will be a high temp process that might warp the cams and lead to still more issues. Or cut the surface down on the journal and install a harder sleeve. We will see how the cam bearings work because it is very simple and just costs a few bucks to install. The exhaust side is pressure fed already but a small oil feed hole needs to be drilled in the intake side to feed that bearing.
I will check the rc on some of the other cams to see what they are at. I have a few stockers that have experience the same problem but they were from engines I bought or ones that had an intake bearing failure. So the R@D continues.
I will check the rc on some of the other cams to see what they are at. I have a few stockers that have experience the same problem but they were from engines I bought or ones that had an intake bearing failure. So the R@D continues.
-
wayneschofield
- Posts: 0
- Joined: Wed Mar 10, 2021 10:41 pm
Nitrided? Are you sure?
They look more like 'Tuftrided', Nitriding normally leaves them with a silver finish...
Nitriding goes much deeper too, around .010" typically, so is not a 'skin' to flake off and cause bearing problems.
Tuftriding leaves the surface a little rough and carbonised, and should be polished off before it is run in a bearing, either plain or roller...
It also causes a slight dimesional change as, during the process, the metal is heated to around 900 deg C in an atmosphere rich in carbon atoms. When the metal is heated to this sort of temp the crystalline structure changes and becomes less compact and more 'open'. This causes the component to 'swell', more than is attributed to thermal expansion, because of the crystalline structure change. This structure is tougher than Iron's normal structure.
The open 'pores' of the of the 'new' structure allows carbon atoms to become 'interstitially' placed within the Iron atoms at the surface and just a few thou below it. When allowed to cool the carbon is trapped and the Iron at the surface is forced to stay in the more 'open' structure. The structure at the surface when cooled, being 'bigger' than the structure below it, becomes in compression, thus making it less likely to fail due to the propogation of cracks. The carbon also makes the surface tougher.
'Parkerising' is sometimes used on cams. This, too, should be polished off on the bearing surfaces. Parkerising leaves the surface slightly porous, so is better at retaining oil if the application is a little oil-starved in service... Parkerising is a dark grey/black finish and looks a little 'scaley'...
Just my 'ten cents' I think you call it...
They look more like 'Tuftrided', Nitriding normally leaves them with a silver finish...
Nitriding goes much deeper too, around .010" typically, so is not a 'skin' to flake off and cause bearing problems.
Tuftriding leaves the surface a little rough and carbonised, and should be polished off before it is run in a bearing, either plain or roller...
It also causes a slight dimesional change as, during the process, the metal is heated to around 900 deg C in an atmosphere rich in carbon atoms. When the metal is heated to this sort of temp the crystalline structure changes and becomes less compact and more 'open'. This causes the component to 'swell', more than is attributed to thermal expansion, because of the crystalline structure change. This structure is tougher than Iron's normal structure.
The open 'pores' of the of the 'new' structure allows carbon atoms to become 'interstitially' placed within the Iron atoms at the surface and just a few thou below it. When allowed to cool the carbon is trapped and the Iron at the surface is forced to stay in the more 'open' structure. The structure at the surface when cooled, being 'bigger' than the structure below it, becomes in compression, thus making it less likely to fail due to the propogation of cracks. The carbon also makes the surface tougher.
'Parkerising' is sometimes used on cams. This, too, should be polished off on the bearing surfaces. Parkerising leaves the surface slightly porous, so is better at retaining oil if the application is a little oil-starved in service... Parkerising is a dark grey/black finish and looks a little 'scaley'...
Just my 'ten cents' I think you call it...