PowerBoatr,

Confusion is understandable at this point….

I have the machinery and the knowledge base to do the work. It’s just that compound angles are complicated and, without knowing what the angles actually are, it’s a matter of tweaking the setup until the existing hole is as close to perfectly aligned as possible for each bank of rockers, for both heads. It’s a lot of tedium. If there were an easier way to do this safely, I’d be all ears.

The heads are good. they were decked with the rebuild last winter. All I need are larger rocker stud holes. I should have done this during the rebuild.

Thanks. Brad.

understand
if you have the equipment and skill.
Bingo
I would practice on a nonservicable head.
i would think the info and math should be available

Sorry, I guess I didnt make the connection And yes, best to keep a subject all in one thread.
With that being said, when I do that job on other heads I do it in my seat and guide machine which makes it very easy to level the head for each angle.

That being said I would really have to wonder if you will have enough thread engagement for the 7/16 Studs ?? A 10mm bolt is .393" od. 7/16 bolt is .437" ? That sure does not leave much thread depth for the 7/16. That would worry me more than the number of threads you have on the polylock.

PowerBoatr,

I can do the math. It’s knowing the angles to do the math with that’s the issue. I have not been able to find that information out there anywhere. Just like the ignition timing, that is unobtanium information, near as I can tell.

I’m used to working on one-off stuff. I’ve been handed a $20K 3DP copper part and contracted to do finish machining on it. Scary as farq, but I do it. And this working WAY simpler than that was.

Thanks. Brad.

Maybe a friendly shop
could shed some light on angles
I would definitely get a sacrificial head to try it on
Good luck

BillK,

The concept of tearing the heads down was the furthest thing from my line, and I didn’t want to suddenly change the direction of conversation in the other thread, even being related as they are.

I’m not sure I’m following. The base threads will have the same 3/4” thread length. We’re just opening up the M10X1.5 holes to 7/16-14. The tap drill for the 7/16” thread is .368”, which will wipe out all but a minimal amount of the original M10 threads. The vast majority of the 7/16 threads will be in new, solid material. Larry at Raylar already asked me if I’d tapped them out for the 7/16 stud bases, so I’m guessing it’s not an uncommon thing. I have asked through email and will confirm before moving forward, however.

Thanks. Brad.

Sounds like others have done it but it sure does not sound like enough thread depth for me. I am seeing the tap drill size for 7/16 x 14 as 23/64 which is only .360" I know that does not sound like much difference but it would worry me. But if Raylar is doing it i guess its good to go.

I definitely would set it up in a machine over drilling it by hand if you have the equipment.

BillK,

I’m stuck with the thread depth, I think. I guess I could see if there is material below the stud to go deeper, but that would only be beneficial if there are studs available with longer base threads, and I’m not sure there are (haven't looked).

The good book says a “U” drill, which is .368”, for 7/16-14 tap drill. The general math rule is the basic thread diameter (.4375”) minus the thread pitch in distance (.0714”), which calculates to .366”, but I have no problem starting with a 25/64” (.359). The more material there is, even if it’s interrupted by what’s left of the M10 threads, the better.

I have emailed Larry about this, in specific, and will get confirmation before moving forward with anything.

Yup. I have the mill and a tilting table. It will just be a matter of finding the correct angle of tilt and rotation of the head on the tilting table to get the existing threads aligned with the spindle of the mill. I would (hopefully) be able to do, say, all the intake studs on one head, set up a set of stops to locate the clocking of the head on the table, then do the intake studs on the ohter head, then repeat the process for the exhaust studs. This should minimize the amount of time spend tapping the head around and tapping the tilting table, getting the existing tapped holes aligned with vertical.

As a side note, I just got a PM from Admin, informing me that I’ve received the “Community Builder’s” badge. I guess I’ve talked enough about doing stupid sh!t like this enough, they thought they’d give me an attaboy star to pin on my cape.

Thanks. Brad.

Thats what is nice about having automotive tooling. I would put one of the existing studs in and use my valve guide level to get it level in the seat and guide machine. That plus having an air float table makes it a very quick process. I could probably drill and tap all of the intakes in less than 15 minutes. I cannot imagine trying to do it in a Bridgeport and having to indicate every single hole

Sounds like you have it under control !

BillK,

I’m running on the assumption that all the intake studs will be on the same angle, and all the exhaust studs will be on the same angle. Once I get one of them trammed in, and picked up the remaining three holes, it will only take a minute or two. Rinse and repeat for the remainder, four at a time.

But….

Since you mention that it is that easy, I will call my tuner, and see what their machine shop can do for me. I like doing these things for myself, but, as I said earlier, it’s always cheaper to buy than to make.

Thanks. Brad.