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Discussion Starter · #1 ·
My aluminum rocker arms have aged out. I have a contact with a cnc machine. I simply can't decide on what to build new arms from. 7075 aluminum, grade 5 titanium, or 4340 steel. Old arms were made with 2024 aluminum.

The Ti and steel seem to be coming in close to the same prices and about 3 x the 7075 Al.
 

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My aluminum rocker arms have aged out. I have a contact with a cnc machine. I simply can't decide on what to build new arms from. 7075 aluminum, grade 5 titanium, or 4340 steel. Old arms were made with 2024 aluminum.

The Ti and steel seem to be coming in close to the same prices and about 3 x the 7075 Al.
If you chose Aluminum make sure you know the "country of origin" there is some real fucking garbage being sent into this country from China. 2024 might be difficult to get right now.
2024 vs 7075
Airplane Flying From Nose View
The 7075 alloy, like 2024, is very common in the aerospace industry. The main reason for this is that it is one of the strongest aluminum alloys available. With precipitation hardening, it can achieve a tensile strength of 83,000 psi and a yield strength of 73,000 psi, stronger than 2024. In terms of applications, 7075 is suited to applications that require high stress/strain resistance. Whereas, 2024 is suited to applications where high cyclic fatigue resistance is required.
 

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I had a machine shop for 12 years and made thousands of rockers. I can't see any instance where making 1 off rockers makes sense. Can't buy replacements? Stud mount or shaft mount?

It would require a minimum of a 4 axis CNC mill. Programming and tooling is a killer. Raw material cost is nothing compared to that.
Ti will be the most durable if the valve train weight is not an issue otherwise 7075 T-6 is the best choice.
 

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Discussion Starter · #9 ·
Exactly the information I was hoping for. Thanks
 

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Discussion Starter · #11 ·
Agree with this. Made FE Rockers out of 7075 and they did not last. Started fatigue cracking
Oh crap. Thanks for posting this and letting me know.
 

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7050 T7451 would be my choice over all others listed in this thread.

2nd choice 7075 T73
 

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Discussion Starter · #16 ·
Thanks guys!
I sent a few pm's
Still the best place to get information!
 
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Worked at a place that had a contract to some NASCAR teams engine programs. Rocker arms were made of steel, CPM M4 and then treatment with chemicals. All were very thin cross section and shaft mounted, with very high rocker ratios. Surviving Daytona and similar tracks, was the point.
The Super Schmoozer Company President had to go once, he sold the company to a Japanese Investor so, I don’t believe the contract is ongoing.
 

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Discussion Starter · #19 ·
What should I be paying for 4340? 1"x2"x48"?
The prices I got seemed insane.
 

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Online metals has 4340 advertised at 1165 (annealed) for 1x12x48 and they'll custom cut. Comes out to about 200 bucks or so for 1x2x48. I don't buy 4340 in plate or sheet normally so I don't know if that's pricey or not.

We have a local Metal Supermarket and I've bought some stuff through them and they've been very reasonable. Might want to try them. BMG is another one.

Where are you located?
 
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