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Old 07-25-06, 07:37AM   #1
GRX
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Question '061' heads - rocker stud conversion?

Have a set of big valve '061' heads. The original open chambers.

My question is .... what is involved converting these heads over to screw-in studs?

Original studs are step type press fit 7/16" dia, which naturally leaves a 7/16" hole when removed. The problem is typical screw-in studs have 7/16" threads. Does someone make a proper stud with 1/2" threads? Or would a set of thread inserts (not Helicoil) in the stud bosses be required to enable use of 7/16" studs?

thanks - grx
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Old 07-25-06, 09:36AM   #2
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I believe there is a stud with 1/2'' threads.
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Old 07-25-06, 03:55PM   #3
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Arp #290-7201 rocker arm studs have 1/2 13 threads with 7/16 20 top threads.
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Old 07-25-06, 07:30PM   #4
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Many thanks for the advice - greatly appreciated.

What disturbs me is the stud hole is 7/16" diameter. Since proper tap/drill size for 7/16-14 thread is "U" (.368) I am not sure there would be adequate material left for a proper thread to hold the 1/2" stud. Which leads me to below ...

Also have a set of '061' that I exchanged for a set of 6X heads many years ago when I ran the shop ... long story. Never used them because I was unsure about the stud holes. I threaded them for use of 5/8" solid thread inserts because I did not like the fit of the 7/16 Helicoils. Never got around to using the heads. Why did I grab them in the 1st place? The 6X were free & couldn't pass up a set of large valve '67 heads. Especially since I knew they were the 72cc open chambers.

Here are some images :

~ stud holes drilled & tapped for 5/8" (7/16 inside) dia inserts :


Yeah, Helicoils are great when installed correctly. Seen grade-8 3/8" bolts broken off in them before so I know they are plenty strong.

Since some of you have used Helicoils in this application, do you think the larger diameter inserts would be OK with big springs? These inserts fit very well. As you can see there is plenty of material left around the hole. Opinions appreciated.

____________________________________________

Image of open chamber goodness. Amazingly the valve seats & ports look to be in great shape except for a little surface rust from sitting. Nobody's gone hog wild yet. As you can see I blocked off the hole to the heat exchanger in the Exh. ports with threaded inserts.



If you think these heads are still usable for a 450- 500 HP engine I might just pass up the other set of '061' and use these.

Last edited by GRX : 07-25-06 at 08:08PM.
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Old 07-28-06, 07:42PM   #5
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Damn! Got my tap/drill sizes mixed up.
"U" is for a 7/16' thread. That is what I get for going by memory.

Well, since nobody has spoke up about how I machined the rocker bosses for the large 5/8" inserts can only assume there are no reservations. Though it would be OK but always good to get opinions from others.

And by the way ..... after closer inspection of that other set of 061 heads I was considering buying, they look to be headed for the scrap yard. For one, someone drilled the rocker stud bosses & installed roll pins in an attempt to keep the press-in studs from backing out. Looks like they did it when the heads were on the car too because the pins are at odd angles. Plus the exhaust valve seats look to be sunken. Oh well, lots of these 061 heads probably had a similar fate. Have seen a couple sets at swap meets & such which never sold. Most people see the press-in studs and move on.
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Old 07-29-06, 12:27PM   #6
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Default sunken seats

You could aleays save them with a seat insert, which you would have to do anyway if you are running unleaded gasoline.

As far as the pinned stud bosses go if there is enough material there to go oversize as you did on your other set they should be ok.
What does "Helicoil" rate the "pullout strength" on the properly installed size insert you want to use.I'm sure this information is available on their website.
Compare their #s with the open pressure of the springs you are thinking about using and that should give you a good idea of the safety margin you can expect.I'm guessing it will be way over and above anything you are gonna throw at it.
Remember that if you were using aluminum heads all the female threads would be heli coiled and both intake and exhaust seats would be using seat inserts.

But if you are wanting absolute peace of mind for an all out racing effort a virgin set of iron heads will give you that?
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Old 07-29-06, 01:45PM   #7
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GRX,were all 061s large valve,open chambers?These are oe on our 67 cat conv.I thought they were same as 143s with old style chambers and small valves.Our cat is the 290hp 2-barrel.Were the 061 a late year head,and 143s early?Thanks Kenny
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Old 07-29-06, 02:30PM   #8
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you can save the other 061's use helicoils or the locking type inserts, similar to what you have, also have seats put in the heads, this would be good for unleaded fuel, which sprint had advised. i have seen a blown 400 using 4x heads that had heli coils, studs and a stud girdle, they had no problem with studs pulling out,even with a roller cam and .600+ lift.
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Old 08-02-06, 05:17PM   #9
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Had to do this to my 1955 heads in order to run roller rockers, i think mine were 7/16 press in's and i needed 3/8 you will need to have the seat machined so that the threaded rocker stud will contact properly. Think i have a picture on here some where of mine after machining


ok its not real clear will have a look for a better one but you can see the work done in this one

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Old 08-02-06, 05:44PM   #10
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ok this should be a better pic
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Old 08-02-06, 05:58PM   #11
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Thanks for sharing the images Starchief. Looks nice. I like seeing those older Pontiac engines even though they don't perform like the later designs. What I want to know is, what did you do about getting oil up to the rockers after that work? Plug up the oil passage in the block and let the oil come up through the push rods instead?

As you can see from the images, the rocker stud pads on the 061 are machined flat at the factory. They do come with guide plates.

Yes ... you gotta have a nice flat machined surface for the stud shoulder to rest squarely against. Cast top stud bosses need not apply. Had to do that converting SB Chevy heads over to screw-in studs at work far FAR too often. The thing with sbc heads the studs go into the water jackets, but that is another story.
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Last edited by GRX : 08-02-06 at 06:09PM.
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Old 08-02-06, 06:09PM   #12
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55 Starchief - off topic a bit about your 287 ....

Just curious ... what would a complete NOS Pontiac 287 fetch these days? Probably shouldn't tell you this, years ago one of my regular customers traded me one for some machine work. Far as I could tell it was completely new - never run.
Well ... I took it to swap meets and advertised it in the papers but couldn't find any takers, not even for $100. Got tired of tripping over it in storage so I ended up junking the whole thing. Ironic thing is, less than 2 months later a guy I saw a swap meet contacted me at work and asked if I still had it since his just blew up. Go figure.
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Old 08-02-06, 06:25PM   #13
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Quote:
Originally Posted by GRX
Thanks for sharing the images Starchief. Looks nice. I like seeing those older Pontiac engines even though they don't perform like the later designs.
Well if all the dyno simulations are correct expected power is going to be around 400hp+. If you throw enough money at an engine you can get it to make power. Have a look at the dyno simulations in the zip file atachment if i can get close to these i will be more than happy

Quote:
Originally Posted by GRX
What I want to know is, what did you do about getting oil up to the rockers after that work? Plug up the oil passage in the block and let the oil come up through the push rods instead?
From memory the cam bearings were installed the wrong way round to block the oil passage. I had to have new pushrods which would oil up through them as the stock ones where not hollow
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Old 08-03-06, 11:47AM   #14
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Quote:
Originally Posted by GRX
Have a set of big valve '061' heads. The original open chambers.

My question is .... what is involved converting these heads over to screw-in studs?

Original studs are step type press fit 7/16" dia, which naturally leaves a 7/16" hole when removed. The problem is typical screw-in studs have 7/16" threads. Does someone make a proper stud with 1/2" threads? Or would a set of thread inserts (not Helicoil) in the stud bosses be required to enable use of 7/16" studs?

thanks - grx
ARP makes a stud for the pontiacs its 290-7201 ,7/16 at the top and 1/2 at the bottom.it does need some mods though, you will need to cut about 1/4 off as the studs are to long and will come through into the intake ports.

To fit these you will have to drill the stud hole deeper in the head till it comes into the intake port and water jacket on the exaust,then machine the stud boss down .250 so the hex on the stud will clear the rocker.

Important dont forget to use sealer on the bottom of the studs or oil will leak into the intake ports and water will seep through the exausts into the engine.

Andy
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Old 08-04-06, 03:25AM   #15
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Quote:
Originally Posted by 55 Starchief
Well if all the dyno simulations are correct expected power is going to be around 400hp+. If you throw enough money at an engine you can get it to make power. Have a look at the dyno simulations in the zip file atachment if i can get close to these i will be more than happy
Heck yeah! That would be some serious power from that engine. Would love to see it run. Would love to see the machine work too for that matter. Gonna have to keep an eye out for that one.

Makes me sad when I think about having to get rid of that 287. Really wanted to put it together and see what it would do but converting the older style engine mounts was something I wasn't prepared to deal with at the time. Then I had to move unexpectedly and some stuff had to go.

That customer used to trade all sorts of old stuff for machine work. Think he traded me the 287 for assembling his Chevy 396. Apparently he bought a house and garage at auction. The guy who lived there previously worked at the Baltimore GM plant which is likely where all the NOS stuff came from. Most of it was Chevy stuff, but there was a little Pontiac mixed in there.

Quote:
From memory the cam bearings were installed the wrong way round to block the oil passage. I had to have new pushrods which would oil up through them as the stock ones where not hollow
Should have known ... that would be the better way to do it. Cam bearings #2 and #4 need the extra holes lined up to the passages. Saw far too many people have oiling problems after installing later style bearings in those older Pontiacs. Many would drive an aluminum plug into the hole by headbolt and use the hollow rockers.
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-M20-, 12-bolt w/3:55s
~ Suck , Squeeze , Bang , Blow... @ 43.33 Hz
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