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Old 04-25-2013, 02:52 PM
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Machining for Pontiac, screw in studs

I called a shop that specializes in machining heads in my area. I've got a set of Pontiac 17 heads that were machined by NAPA about ten years ago. Got'em off Craigs. I am getting this cam set from Lunati, 10510701K. 5200 RPM. Springs need screw in studs.
The shop quoted me at 125 to install studs. Here is the part I don't understand. They said something about 7/16 and needing Heli-Coils possibly, which would raise the price to 250. What does this mean?

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Old 04-25-2013, 03:38 PM
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Possibly that the existing pressed studs are 7/16, that hole would be too large to cut threads for 7/16 studs?

For instance a 7/16-14 NC stud requires a smaller 3/8 drill/hole. A 7/16-20 NF requires a 25/64 hole.
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Old 04-25-2013, 04:19 PM
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Option #1:
Use ARP 290-7201 rocker studs and you will not have to install heli-coils. The threads of those studs is 7/16"-20 adjustment threads x 1/2"-13 base threads. All that is required is to tap the stud holes for 1/2"-13 threads and eliminate the heli-coils. Eliminating the heli-coils will help pay for the ARP rocker studs which cost about $100 a set of 16. The base threads will break into the top of the intake ports but that is not a problem.

Option #2;
Purchase BB Chevy stock replacement rocker which have 7/16"-20 adjustment threads x 7/16"-14 base thread for about $25 a set of 16 studs. They are available at most local parts stores. You can then recover some of the cost of having the 7/16"-14 heli-coils installed.

The installation of either of those studs will require machining the stud boss flat and down 3/8".

Last edited by MouseFink; 04-25-2013 at 04:32 PM.
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Old 04-26-2013, 08:32 AM
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A couple minor things...

We HeliCoil this operation because the original holes are the correct tap-drill size for the HeliCoil. When properly done, HeliCoil is stronger than iron threads. This should NOT be attempted "by hand".

The ARP studs MF speaks of will "work", but there are some quirks. The guideplates must be opened to allow the 1/2" bottom,. The threads are 1" long, requiring either a deepening of the hole or shortening of the stud. Why they have such long base threads is a "mystery" to all but ARP. Maybe something to do with the early SD stuff. We are installing a set in some 389 heads right now, at the customer's request.

The 17s have guideplates, so there is no need to mill the stud bosses. In fact, if the HeliCoil method is employed, the original bottle-neck type stids from the performance heads can be used, maintaining the non-adjustable valve train (stock). For hydraulic flat tappet cams under .500" lift, this is a good thing.

NOTE: Keep the factory guideplates. Most aftermarket versions are inferior or don't fit properly.

Jim
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Old 04-26-2013, 10:49 AM
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IIRC originally the 17 head had pressed studs, so guideplates aren't held down by the studs from the factory. They're small valve 350 heads, 2 bbl apps.

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Old 04-26-2013, 12:47 PM
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Correct. Studs are pressed. This is not a Chevy. The bosses are already milled "down", and the guidelplates are held in by two 5/16" bolts on each one (same guideplate as the screw-in stud heads). Trust me on this... The pushrods, rockers, etc. are all the same, regardless of stud type.

Jim
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Old 04-26-2013, 02:48 PM
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thanks for all the info, really making me rethink my options here.
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Old 04-26-2013, 05:50 PM
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Yes on the ARP studs. I have them and they are working well.
They are pretty long, so long in fact that in a few of the intake and exhaust ports the new holes went through into them. Be sure to use Liquid teflon to seal them.On Holes that are " Blind" just torue to spec.
X 2 on the guideplates. Using a drill press and a 1/2 inch bit carefully does the trick.
One other thing , The ARP studs on the rocker stand side were almost too short for posilocks. I was able to use a hardened washer on top of all my rocker arm balls, raising up the adjuster nut part , and that was enough to give me 3-4 threads for the inner lock Screw . I also used Locktite on the lock nuts. I very Carefully adjusted the valves , one cylinder at a time, before I broke the engine in.
I adjusted my valves at 3/4 turn past zero lash, It did the trick.
The engine runs like a beast.
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Old 04-27-2013, 12:55 PM
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buying a set of heads off craigslist, and trusting them are 2 different monsters.

have them checked! make sure they seal and they are not cracked!

i always start with a set that has screw in studs to begin with. one process eliminated.

also, have your pushrod clearence holes enlongated for clearence of larger ratio rockers. if you decide to upgrade later.
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Old 04-27-2013, 01:19 PM
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Quote:
Originally Posted by h0trod View Post
buying a set of heads off craigslist, and trusting them are 2 different monsters.

have them checked! make sure they seal and they are not cracked!

i always start with a set that has screw in studs to begin with. one process eliminated.

also, have your push rod clearence holes enlongated for clearence of larger ratio rockers. if you decide to upgrade later.
I agree with that.

However, the GTO/Firebird 400 heads with large valves and screw-in studs are becoming rare and expensive. If you happen to find a pair, they need to be checked very closely before you buy them. Pontiac discontinued those heads 40 years ago and the survivors have been rebuilt to death.
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Old 04-27-2013, 01:48 PM
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Quote:
Originally Posted by MouseFink View Post
I agree with that.

However, the GTO/Firebird 400 heads with large valves and screw-in studs are becoming rare and expensive. If you happen to find a pair, they need to be checked very closely before you buy them. Pontiac discontinued those heads 40 years ago and the survivors have been rebuilt to death.

this why it pays to be a hoarder! i have collected 2 sets of 16's 2 sets of 62's, many 6x4&8's 6s's
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Old 05-15-2013, 01:22 PM
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If I had Option 1 done to my heads, installing the BBC studs with the 1/2 base, besides probably changing out push rods, would I have to change out the stock rocker arms? Ream out the guide plates? Just trying to figure out the total cost involved.
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Old 05-15-2013, 02:09 PM
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Use ARP 290-7201 rocker studs but be prepared, they copst about $100 for 16 studs whereas BB Chevy rocker studs cost about $20 a set.

The ARP studs are not BB Chevy rocker studs but are studs designed by ARP specifically for Pontiac heads with pressed in studs. That is because the holes left in the heads after removing the pressed in studs are too large to tap for 7/16"-14 BB Chevy style rocker studs and a 7/16"-14 heli-coli must be used. You can eliminate the heli coil step by tapping the head for 1/2"-13 threads and using ARP 290-7201 studs.

If you decide to use BB Chevy style rocker studs, don't use heli-coils, use E-Z Loc thread inserts.

I have used the ARP 290-7201 studs on 1963-1964 GTO/421 HO Pontiac heads where you must mill the stud boss 3/8" and then tap the stud hole for 1/2"-13 threads. The 1966 and earlier heads do not have a stud boss that is milled for guide plates, instead the push rod guides are an integral part of the heads. Be advised, ARP studs have 7/16"-20 Class 3 rolled threads which are not designed for BB Chevy 7/16"-20 prevailing torque locking nuts. You should use full roller rocker arms and poly-locks with ARP studs.

The stock Pontiac rocker arm slots fit the shank of ARP 290-7201 7/16"-20 x 1/2"-13 screw-in rocker studs, stock 3/8"-24 x 7/16"-14 Pontiac bottle-neck screw-in rocker studs or GM BB Chevy 7/16"-20 x 7/16"-14 screw-in rocker studs. No problem there, but read and heed the last two sentences in the previous paragraph.

1967-and later Pontiac heads used guide plates and they will fit stock or aftermarket hardened 5/16" Pontiac push rods.

Last edited by MouseFink; 05-15-2013 at 02:18 PM.
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