Race Engine Forum UK

Hi.

Apart from a cam's profile, how do you select a cam based on the quality?
Every cam maker will tell you their's is best, but what makes one better than the other? ie: cast/chill-cast/forged/heat treated, quality of metal etc.
Am I likely to be told what goes into making there cams, or how well they will wear?

Many thanks

No, you won't be told how well they'll wear, for sure! You might get told what they're made of. If you pay enough, you can get them made out of anything you want, within reason.

FWIW I've seen a high degree of survivability and the same wear characteristics among all the different types, chill cast-iron, heat-treated (HT) by means of nitrided/plasma nitriding/cng/tufftriding, using anything from En351 to En40B and En24T.

Now, notwithstanding how soft the cams are compared with HT steel, half the world uses cast iron cams because of low price. And why not? Take OE TC cams; after all - they seem to last a very long time indeed if kept lubricated and shimmed properly. The TC oil bath setup with its case hardened shims running against cams-of-any-material is exceptionally good. All Abarths 8v, 16v 124/131/037 cams were cast-iron.

Nitrided En24T is probably the most durable (and expensive) material for cams, better than 40B, the nickel content it forms hard nitrides or so my metallurgist tells me. But mostly people use steel because they cannot get good cast-iron chill banks or because they want special design features. And making heat treated cams is not easy, many steps of HT and machining/grinding, all requiring a lot of experience, precision and process controls.

Mostly the biggest problem with cams is the guy fitting/using them, I can say that. And there are certainly always new & interesting ways to 'wipe out' a cam..


GC

Need I say it, but thanks once again Guy

I would like to know why the cams on the Tipo 16v for example are extremely soft in material compared to 8v engines?? You can take an edge off with a file very very easily which makes me wonder if there is a reason?

Andy.

Just don't know about the difference between them Andy. Sure, cast-iron cams are very soft generally, but having such a high level of graphite in them makes them oil retentive, this is inherent and the reason why cast iron runs so well as a cam material. Whereas steel cams are not oil-retentive and have to be heat treated to achieve that.

GC