Guys,

During my cam swap, I discovered that the builder who rebuilt my engine last winter reused the TTY head bolts and, apparently didn’t use either enough or the right thread sealant, and I had a minor coolant leak, at least on a couple of the exterior head bolts. So I set myself to replacing them. I have a set of re-torqueable head bolts coming from Raylar. But I keep obsessing over the rocker arm geometry. ARP has rocker studs that would solve my rocker geometry issue, but they are 7/16-14 base threads. So now I’m considering pulling the heads, disassembling and tapping them accordingly. So….

Anybody ever drilled and tapped 496 iron heads for 7/16 stud base threads? Did you do it by hand? I can clearly see that they are on a compound angle. I have the tooling to tilt and orient them to “find” hole alignment. Then it would just be a matter of picking up each hole and making the chips. I’m just curious if there’s an easier way that is sufficient.

Thanks. Brad.

He re-used TTY bolts....wonder what process he used to 'tq' them.

You can drill/tap rocker studs but they should be on a machune of some sort to correctly align them.

Assuming your machine shop would be able to take care of that. A well setup dril press with angle capacity and proper rpm. Correct tooling. Maybe easier to just get them done after the capital costs for the tooling. One less issue you need to focus on.

But it is certainly possible. The multi angle BBC valves/studs make it a far more complex job than a SBC head.

Cyl Head machinery has the setup to align the angles required.

Tartilla,

No idea. It obviously worked. I don’t really know for sure, but looking back through our texts, makes it appear as though he did. Otherwise, the engine was running fine, coolant seep aside.

I AM the machine shop. It’s what I do for a living. I have the mill and a tilting table, and the knowledge base to do the work. I also agree that the precision is an important aspect. But I’ve also seen drilling/tapping guides/jigs that are used for this job to be done with a drill by hand. I just didn’t know if one existed for this head.

Thanks. Brad.

https://goodson.com/products/s-450-r...conversion-kit

Goodson is often overly expensive. You may find better rates from other cyl head tooling suppliers.

Your bolt holes are 10mm vs 3/8"?

Wouldn't it be easier and less risky to machine a set of custom M10 studs?

Tartilla,

I don’t need the tooling. We’ve got all that. I was hoping for a drill/tap guide that would save me a bunch of setup time on the mill. But, with the compound angle of the stud holes, that’s probably not a feasible prospect. Nothing worth doing is easy, I guess.

Thanks. Brad.

Markus,

Been down this road. Aside from the fact that it’s always cheaper to buy than it is to make, the cold forming and rolled threads make ARP studs WAY stronger than what I would make, even if I got their metallurgy and heat treat perfect. The infuriating thing is that ARP has studs sitting on the shelf that would satisfy my needs, but they were from a “custom” run, and they want that same “custom” pricing for them they got from whoever ordered them to begin with, which is ~$800 for a set. Nope. Just farq that. As it is, they have studs in their normal inventory that will satisfy my needs, but they have 7/16 base threads. By far, the easiest route is to open up the holes in the heads for the larger threads and order studs. That’s what we call a “metal off” solution. Machining is what we do. This is just another Tuesday for us. Plus I get the bonus advantage of the considerably stronger base threads. Still chewing on the prospect, but I’m talking myself into it.

Thanks. Brad.

ARP makes a set of studs with the 10MM bottom threads.

https://arp-bolts.com/kits/arpkit-de...p?RecordID=393

Confused now
is or does the OP have the equipment to drill and tap the iron heads?
If so.. set up and do it.
If not
I agree the machine shop that does this relatively easy procedure once the gear is dailed in, is the way to go
heads are off, right
a bonus is at machine shop
They can bring head back to square if needed and check everything thing else
Yes its money spent
But as a mechanic...having right tools and expertise.
is a better route
However if those cost exceed the cost of a new head already done...its an easy go
drilling cast iron is not hard
Getting hole right and perfect...is what's important
following

BillK,

Maybe I should have just stuck with this thread…

I have that very set on my heads now. It’s the installed height that is the issue. When I establish “perfect” rocker geometry, I don’t like the thread engagement of the polylock nut. And that’s where this thread starts.

Thanks. Brad.