Broken camshaft

[Foxie]

Yes Rohan, I just checked. My 450 cam is steel and costs ?366 (each !) There is a cheaper option for a Chilled Cast cam at ?258.

So I will sleep easier tonight......

Sean

[rgh0]

Hi Sean

While you don't need long bolts for high lift steel cams you have the challenge of getting the cam and follower to bed in properly which is why I prefer cast iron cams

You will be using thinner steel followers with a high lift cam and the steel cam on a steel follower can lead to "galling" especially during run in. Galling occurs where you get micro welding between the 2 surfaces which rips out micro chunks of metal leading to the surface failing on run in rather than polishing. Steel is much more prone to micro welding than cast iron and steel on steel is worse than steel on cast iron

There are a number of techniques and things to be careful with to avoid this problem which are especially important to follow when running steel on steel but good practice even if running a cast iron cam on steel followers.

i.e.
Ideally you should have a 10 Rc hardness difference between the cam and follower
Make sure nose load on the cam is less than 200 lbs ideally and certainly less than 220 lbs
Phosphate treat the cam and followers. An alternate is DLC ( Diamond Like Coating) treatment of the followers
Use lots of good assembly lube on the cams and followers ( Redline do a good one)
Use a high zinc running in oil in the engine or conventional mineral oil with added zinc ( only needed during run in)
Avoid idling the engine for more than a few minutes at a time until the cams are run in.

cheers
Rohan

[SJ Lambert]

To modify the cams, set up in the lathe and relief drill to remove the existing thread and enlarge the "barrel" of the cam to accommodate the unthreaded section of the 75mm UHL "long" bolt and drill to tapping size to just beyond the end of the bearing for 7/16" UNF (in the example cams I'm looking at, it'll be drill to tap size a further 25mm so that it'll accept the bolt) is looking like the go to me.

I presume threading the bolts further up towards their heads is not necessary.