[Johnny406]

Several years ago I made a very bad decision when I decided that I could carefully and accurately pull the pressed studs in a set of #47 heads and tap them myself (1/2-13) for screw in studs. I really thought I had them "close enough" so I could use Magnum style fulcrum rocker arms. Long story short, these heads sat for years until I put them on the 350 Pontiac I built for my son. Upon breaking in the engine, it didn't take overly long to drop a couple of cylinders after the poly locks vibrated/backed off from the geometry not being "close enough." I suspect I'm screwed but I used a conversion kit stud like these that do not have the 11/16 base so I used a pair of 7/16-20 lug nuts jam nut style to screw them in. Do you think there is much of chance that if I used the black ARP studs with the 11/16 pad, they would better center themselves?

[Jack Gifford]

No. Converting to screw-in studs is best done on a milling machine (or a rare jig-boring machine).
I haven't handled #47 heads- did the factory machine the tops of the stud bosses? If not, how did you machine them? The studs with integral jam nuts depend on the tops of the bosses being precisely flat, and square to the studs' centerlines.

[ponyakr]

I'm just curious as to how a poly-lock could back off, if the inner lock screw was tight enuff to begin with. I found that AFTER I tightened the inner screw all I could with an allen wrench, I still needed to turn the outer nut a little farther, so that the lock screw would dig into the top of the stud. Since beginning to do that, I've never had another poly-lock to back off.

BUT, if you only tighten the inner lock screw with an allen wrench, & do NOT tighten the outer nut a little more, there is a very good chance that some of the nuts will back off.

All my heads had factory screw-in studs. I never tried to tap holes for conversion studs.

That's my experience. If it doesn't apply to your situation, just ignore it.

[Johnny406]

Originally Posted by Jack Gifford

No. Converting to screw-in studs is best done on a milling machine (or a rare jig-boring machine).
I haven't handled #47 heads- did the factory machine the tops of the stud bosses? If not, how did you machine them? The studs with integral jam nuts depend on the tops of the bosses being precisely flat, and square to the studs' centerlines.

These heads came with factory guide plates installed on them.

[Johnny406]

Originally Posted by ponyakr

I'm just curious as to how a poly-lock could back off, if the inner lock screw was tight enuff to begin with. I found that AFTER I tightened the inner screw all I could with an allen wrench, I still needed to turn the outer nut a little farther, so that the lock screw would dig into the top of the stud. Since beginning to do that, I've never had another poly-lock to back off.

BUT, if you only tighten the inner lock screw with an allen wrench, & do NOT tighten the outer nut a little more, there is a very good chance that some of the nuts will back off.

All my heads had factory screw-in studs. I never tried to tap holes for conversion studs.

That's my experience. If it doesn't apply to your situation, just ignore it.

It's the first time I've ever had poly locks back off. The roller tips were not as centered on the valve stem as they should be, that's when I realized I made a bad decision to tap them on a workbench.

[Cliff R]

An easy way to convert to screw in studs is to obtain a block of aluminum wide enough to span across two adjacent studs. Drill it to the diameter of a stud or 7/16" in a drill press. Come over on center the exact distance of the adjacent stud and drill a straight hole then run the desired tap thru it. For Pontiac heads you can go up to 1/2" and buy conversion studs or heli-coil back to 7/16" and use straight wall studs.

One stud is pulled and your aluminum block slides over the remaining stud and lines up the tapping operation on the adjacent hole. Once complete install a stud there, then pull the stud you just used as a guide, slip your tool over the screw in stud and tap the hole you just pulled the stud from. Work your way down the head swapping your guide tool back and forth until you get all of them tapped for screw in studs.

I made a block for SBC heads nearly 50 years ago and another one for Pontiac heads about 25 years ago. Don't use them much these days as I've been sending heads out and let folks who port and rebuild heads for a living do all that stuff, but they are pretty easy to do yourself even if you don't have access to a mill........Cliff

[Formulas]

When I did my #47s I used a aviation structure tool called a Steamboat. Snatch block, Bushing block, bolt it down to the head or use a big C'clamp what it does is keep whatever your doing drilling or tapping at a 90° angle to the work surface

That said ball socket pushrod and ball socket rocker fulcrum should allow you some variation in your results without catastrophic results, full roller rockers will transfer the misalignment to the rocker body more depending on which way the stud is off.

I would re,adjust and make sure poly,locks are tight before throwing in the towel or try cinch nuts

[Johnny406]

There are about 3-4 of them that you can clearly see the center of the stud if well off the center of the valve stem. When I did this many years ago I had the leads leveled and used a level drill and tried to make a jig but it wasn't as successful as I had hoped.

Anyways, I took the worst one and tried to bend it on the head with my engine hoist handle, it didn't budge at all but the handle is now bent LOL.

I was thinking of pulling off the heads and perhaps using a stud girdle as a template and perhaps using a oxy/acc torch to heat up the studs down low and carefully center them on the girdle?

[tom s]

Pull the heads and take them to a good machine shop and see if he can get the deal addressed!JMO,Tom

[b-man]

Originally Posted by tom s

Pull the heads and take them to a good machine shop and see if he can get the deal addressed!JMO,Tom

This.

However you must now decide whether or not the cost can be justified. At this point I’m thinking the best repair would be to install 7/16-14 Timeserts thereby eliminating the crooked tapped 1/2-13 threads. Hopefully the O.D. of the Timeserts will be large enough to accomplish that. I would do all 16 stud bosses, not just the 4 suspected crooked ones.

By using 7/16-14 inserts you can then buy the much less expensive BBC style studs and not the adapter studs with the 1/2-13 bottom threads.

I converted a set of #66 455 heads to screw-in studs exactly as described above by Cliff R, tapping the holes 1/2-13 to full depth without snapping off the tap was my biggest fear. By working slowly and carefully I was successful, but it was tiring running both the starter tap and bottom tap down all 16 holes making me think next time just pay a shop to do it.

[JD311]

When i was in High School (around 91), my Dad and I converted a pair of 061 heads to screw in studs. I didnt have much money then. so we used stock “bottle neck” screw in studs. We did it all by hand, never used a drill or tap guide, drill press etc. never had a problem with the pattern or wear on those heads. Later converted to bbc studs. Sold these to my friend a few years ago, my brother ported them and he put nice valves in them. I had bought them from his grandfather from a wrecked executive (whole car). Anyway, thats my story lol. BTW, we used heli coils in them.

[Half-Inch Stud]

Must have the HEX Stud for Getting & Holding TQ to Factory TQ Spec.

HEX !

[Formulas]

I wouldn't try to bend a stud on the head the power it would take to bend a stud that way might also just be enough just to break the head

[Johnny406]

I see I got bumped/downgraded/relocated to the street section. Honestly, this motor is for the 80 Formula we're building for my son to Jr. Street Drag Race this year after this crisis ends and the track opens up...and I failed/forgot to mention I spent many hours going Pete McCarthy on them LOL...

I've been in the garage studying this predicament that I put myself in. One thing I noticed after popping off one of the bolt down guide plates is that the shoulder above the 1/2-13 threaded section wasn't seated to the base so I went back and further tightened the studs and they did center themselves a bit. Not perfect but a noticeable improvement. I then took a stock rocker arm with a stock non-grooved fulcrum/ball and it lined up much better than the PRW version of the Comp Magnum Roller Rockers do.

With that said and studying what our Pontiac friend Geoff from Down Under took the time to write me is to perhaps tune it a little with the guide plates as well. I think it's going to work out okay, with the shorter stock fulcrums compared the grooved ones, it now gives me enough clearance to run either locking nuts or stay with the poly locks.

Lesson Learned Though: I'll NEVER tap my own rocker stud holes again!

[Johnny406]

This is the worst one, I just have a regular used stock one on it to check the alignment. I didn't touch/tune the guide plate. I'm thinking of just bending the ears on the guide plate ever so slightly and buying a new rocker arm for that one and see what happens, thoughts?

[Navy Horn 16]

I'd just like to congratulate the poster for admitting he made a mistake. Rare as hell in this day and age. I hope you get it sorted.

[Half-Inch Stud]

Originally Posted by Half-Inch Stud

Must have the HEX Stud for Getting & Holding TQ to Factory TQ Spec.

HEX !

Please heed the need for the proper Rocker Studs. Can some PY member send him a used set for free?

[Jay S]

If you bend/adjust the guide to line up the contact make sure it isn’t sliding the rocker on the valve as it is opened. That was probably why the poly’s worked loose. Adjusting the guide could still have issues there, it will be over compensating to get the geometry lined back up.

Probably need to helicoil that bad one to straighten it. No good way to patch that.

[Formulas]

It's been my experience that if you look critically at enough Pontiac heads the studs, valves and pushrods are not all in perfect alignment many times
After all it was mass production and at a certain point it costs more to make everything dead on perfect vrs dealing with comebacks in warranty

That's why on a old original engine you look at rocker arm wear at the valve you will see a wide variations of patterns

[Holeshot71]

Originally Posted by Half-Inch Stud

Please heed the need for the proper Rocker Studs. Can some PY member send him a used set for free?

+2
How are the studs in the pics posted being retained? The correct rocker studs will have a hex to tighten the stud and clamp down on the guide plate.