Rocker Arm holes

[Kart21]

I just bought a set of Brodix ST5.0 heads. These will go on the little motor to get the car moving ( 302 cid .040 overbore with a .016 stroker crank ) with plans to do a 351 plus motor later. ARP head studs, bushings and washers to make the difference in the headbolt diameter. 7/16's Rocker studs and guide plates. Here's the rub, have a new set of forged Erson 1.6 roller rockers but they are for 3/8 studs. No fit the new rocker studs.

I am a machinist by trade and my plan is to open up the 3/8 holes to 7/16. I know the trunions are case hardened but I ordered a 7/16 solid carbide end mill to take out the 1/16 of material. Got a Bridgeport mill and can aline the holes within .001. I just want to use these new rockers and not spend more cash on things I own now.

Does anyon see a problem with this plan ? I will have to get the push rod lenght after I put things togeather no matter what.

What youall think ?

[broke again]

a set of 3/8th studs would have been bout as cheap as the carbide in mill and a hell of a lot easier to swap.

[91CoupeMike]

Let me know how those heads run, I have the same heads ready to put on my car.

[jyro]

take back the endmill

forged Erson 1.6 roller rockers but they are for 3/8 studs. No fit the new rocker studs.

replace the studs, no chance of milling the trunions off center or putting metal in the open needle bearings right next to where your milling. When you cut through the hardened trunion you weaken it, they are hardened after machining for a reason.

[Kart21]

The 3/8 studs are way too short (1/4 inch ) . Was planing to take the rockers apart when I mill them. Its only .031 per side and i can get them alined within .001 with out any trouble. WON"T be running a roller cam, but a flat tappet mecanical, Per the vintage racing rules and nothing over .525 lift.

Just another step in the build, anymore input would be good.

Option B : I could just E.D.M. out the holes. I would just have to make a couple of carbon sinkers for the guy. Easy for me to make.

Thanks Guys !!

[turbostang]

While I certainly don't doubt your ability as a machinist - I do doubt the longevity of the modified trunions.

There's no way I'd tackle machining individual trunions, espeically if the rockers were not disassembled. You'd have to put them in your mill vise along Y and let the rocker body flop in the wind while you cut the trunion. (bad idea).

If you took the time to disassemble them and do it right, you're out a LOT of time. Time = money. If it doesn't save me (or make me) the equivelant of 30-40$/hr, I don't do it. You'll have to set the Z axis of the trunion square first, then sweep in the hole every time - Time is WAY too valuable for that.

As Jyro said, case hardening (as you know) is usually very shallow and if you cut .03125" from each side of the stud bore, you've cut well beyond that, same for the face where the poly lock will sit, as you'll have to reface it as well.

Last but not least, and already pointed out - I'd be looking at returning that end mill, as it was more than the studs cost, especially considering possible future problems. You can get studs anywhere, in just about any reasonable length. A cam that's only .525" lift won't do any damage to a 3/8" stud in a lifetime.