Rocker arm help

[a.middleton]

Rob
My other passion is racing a CCM of which the 4 valve version eats it rockers after about 8 hours use.
The guy (Mark Cook CCM Britain) I get all my CCM spares from has just finish re manufacturing and re designing a supply of rockers for the 4 valve engine and the workmanship is first class. I know he will take on small batch work but it wont be cheap but could be worth a chat. A word of warning though they never answer the phone so leave a message and they will get back.
Andy

[john.whiting]

I think I would be looking at car rockers,possibly from the ninetys,when 2valve motors were still in force.I reckon if I was still in the auto repair business ,I would find rockers to suit without any trouble.Before you say they wont stand the revs,a lot of cars rev higher than any thirties bike ever did.The rockers would need to be made from forged steel,an investment casting would not have the fatigue resistance. A 90ton steel would be 3 1/2 % nickel steel,something like most motorbike stressed components were made from up to the fifties. .The high nickel content makes it expensive,so steels like 4140,4340 and 8620 have taken over.The forging and machining cost for a one off would be astronomical.Regards John.

[Rob Caldwell]

Hi Rob & John, Rob thanks for the name of the CCM man, I'm still hoping beyond hope to pick up some spares but if not he may come in handy, I know one off's are going to be pricey but an engine without rockers aint much use (that's what I tell the misses). John, thats very interesting you mension 4340 which I belive is equivalent to EN24, if that's the case then I'm fairly confident I can make them myself, it will take some time but think of the satisfaction. What I need to do is establish that they are equivalent.
Thanks Rob

[john.whiting]

You can buy hardened and tempered 4140,Rc around 41,[4140HT].It machines well with insert tooling,can be drilled with ordinary HSS drills,and has tensile strength in the 800-900 MPa range.Not forged ,obviously,but if you make them yourself,and eliminate expensive heat treatment,then a failure is not a disaster.Incidentally,you can buy rollers with tiny needle bearings,quite readily.If you are happy to go with Harley size rollers,they can be bought easily,as can Indian size rollers,all with needle bearings and pins.Regards John.

[brenton.roy]

Hi Rob, have you considered hard chroming and re grinding them?
Otherwise, Franklin cams in New Zealand do stellite and hardening.

[nevhunter]

You are likely to get a more reliable job by machining from billet alloy steel and heat treating it. It's the tensile strength you are after. EN 26 was ok for conrods, but there may be something better in the chrome molibdenum alloys. Nev