I searched the internet high and low and could not find what I was looking for so I did some research of my own. I have a 57 gmc wrecker(looks like mater from cars) with a pontiac 347, its a shade tree re-build from my garage and it runs pretty good, mild cam, fresh springs, and lifters but very original. For the last year I've had an intermittent hot tick in the valvetrain and I was planning on adding shim to get more preload on the lifters. In the past I bought some PRW Roller tip rockers and realized the geometry was completely off even though it was advertised to fit. I drove the truck on power tour west with the interment tick and it did fine. But, when I opened up the valve covers I had one slightly broken rocker on each side and the research began. There wasn't enough preload and the valve stem was hammering the rocker arm basically due to wear on valve stems, rockers, push rods, etc... I bought a few single rockers arms to see what would fit(sbc, sbf, late pontiac), turns out a SBC summit roller tip rocker arm works great! my 347 has 3/8 studs that neck down to 5/16 but the 20ftlbs torque spec wasn't working out. I found 5/16 polylocks on summit and used the stock hollow 1957 rocker balls as they were the tallest I had. I could have used the new rocker balls that came with the lifters but i would have needed a 1/8-1/4" shim to add pre load with the bottle neck studs because the polylock would bottom out with out loading the lifter. The combination is nice and quiet and runs great. I have no oiling issues using stud and push rod oiling. In the process I also found some 1955 rocker arms and hardware incase nothing worked out I would still have a useable rocker arm and figure out preload again. some of what I found (basic non precise measurements) - 1955-1959 rocker arms are all the same oils through the stud, no hole in rocker arm, approximate push rod cup to rocker tip center to center is measurement 2.25" - 1955 rocker balls are different from the rest, oil grove present, slightly shorter (.471") - 1956-1959 rocker balls are hallow and taller (.515") - 1955 has longer hollow push rods 9.28" (1955 uses a different lifter) - 1956-1959 9.13" hollow push rod - late pontiac push rod 8.68" - 1955 uses 3/8 studs with 3/8 lock nuts (oval type) - 1956-1959 use special 5/16 nuts to work with the bottle neck studs (20ftlbs tq spec.) Im running and howards rattler flat tappet cam, .488 lift, crower lifters, comp valve springs, and a trick 2GC 2 barrel. It sounds good, I hot rod it around from time to time and it really surprises people to find out its a pretty original pontiac. I've put about 7k miles on the motor since I slapped it together. This was a round about way to make things work for me with out removing the heads and taking them to a machine shop. If you're in my situation or on a budget this will work, but its always a gamble with the stock studs pulling out, if any issues arise again i'll pull the heads and have 7/16 studs put in by a shop and have peace of mind. Also I didn't look at much past 1959 so I have no idea, there's plenty discussion on that stuff around hope this helps -James
I think you can probably extend the "early" year interchangeability out to 1960 for rockers and pushrods. There were significant head changes in 1961 which might then break interchange (not positive on impact). I am using SBC rockers on 1960 heads and they appear to be drop in replacements, although I have changed out the studs to allow for lash adjustments and pushrod oiling.
That’s great information, thanks for posting it. There isn’t a lot of info about what works with early Pontiac bottleneck studs. I have a ’59 389 in my Stude pickup and a ‘62 389 at the machine shop for general rebuild machine work. The rocker stud question came up and I still haven’t decided how to handle it. Part of the issue is how to effectively clean out the oil passages in those heads after years of sludge. He has a couple different types of old NOS Dorman screw-in studs that might work. One type is similar to a carburetor stud in that they don’t have a wrenching “nut” incorporated into them. But they are hollow with oil holes for the ball. The other type is the same but with no oil holes. We figured on using the solid ones and converting to pushrod oiling but hadn’t yet figured out what rockers and balls to use. Any suggestions? Is there a source for the correct Pontiac rockers, balls and nuts? I could just clean the best I can and leave well enough alone. My stock rockers, balls are nuts are worn and rusty. Again, thanks for a helpful thread.
If you are interested in some additional input on the early rockers and the studs, you might log on to the Ames Performance site. You get to the tech info by clicking on the blue box on the upper right and you will see enthusiasts. Click on that and you will see cool links. Should be able to navigate from there. This is an all Pontiac site with lots of knowledgeable members. Just a suggestion.
I think your best bet would be to get all new screw-in studs installed by a machine shop, tap and plug the oil passage on the deck on each side of the block, get some small block chevy rocker arms of your choice. Pick up an adjustable push rod length checker, and order the correct length push rods. With new non-bottle necked studs you'll have the full range of adjustment on the studs you can run the supplied rocker ball with the new stud(using polylocks or locking nuts), or a full roller rocker setup, just keep in mind valve cover clearance, you don't need guide plates on the early pontiac the holes in the head guide the push rods. With a high lift cam the holes can be elongated to account for the extra movement. parts I bought from summit were: push rod - MAN-25726-16 rocker arms - SUM-141706PL poly locks - SDM-PCE255-1001 push rod length checker - CCA-7704-1 I couldn't find a guaranteed supplier for old stuff, some stuff said it would work but it didn't or the picture looked wrong, rocker arms especially. I have gathered myself up a decent supply of stock spare parts but I'm saving them for a future build. Im hoping to get a 1955 or 56 and a 1959 or 60 pontiac car some day. I would definitely check your push rod length, I had 2 that were short and those were to the 2 giving me problems, you could add length to the pushrods or shims under the rocker nuts to add preload with the stock setup, you will want .020-.050" preload depending on the hydraulic lifter. Some of the old parts stand the test of time, I commandeered the wife's old crock pot and cook parts on high with simple green and whatever is lying around, works pretty good!
I would suggest carefully comparing the 61+ Pontiac and SBC rockers to see how close they are. For 55-60 Pontiac they seem to have the same geometry. From another source I have seen rockers are interchangeable 55, 56-60, 61-64, 63 (421 HO)-64 (GTO, 3X2bbl)-65-66-67, 67-76. I have heard horror stories of having to relocate studs and/or changing stud angles to get things to work but that does not seem to be needed for 55-60. For early (55-60) heads I think BBC studs without the hexes can be made to work if you helecoil the heads for them (need to verify geometry though). I ended up using some ARP studs (no helicoils as had one end larger), but had to substantially modify them (details posted elsewhere on HAMB).
@Bird man came to the rescue for us when the torque wrench malfunctioned and my wife broke/twisted off a bottle neck stud on our freshly rebuilt '56 years ago. He found us a few replacements he could extract from a junk yard head and sent along some extra used balls and rockers. I had/still have an eBay search and in the 10 years since only a single three pack of NOS studs has popped up (I bought them just in case). When we built it we used roller lifters but could not figure out how to get roller rockers. Our original rockers were so bad they all really need to be replaced. We went with a new set of stock rockers from Kanter. Two of them did not last 5000 miles. Cracked at the ball socket. We dug through the old original parts and the ones from Bird man we had saved and got out the best two we had and put them back on. Good thing I never throw anything away. I will print this new knowledge and stick it in the glove box for the next time I get into this motor. Side note, all these years later my wife still keeps an extra stud in her purse. It has caused a few issues at security checkpoints as it kind of looks like a bullet on a x-ray machine.
Sort of related, I have a 68 400 engine (in my 68 GTO) and many years ago I bought some poly-locks that thread on the stud and then have larger diam to go over the shoulder. This allows me to adjust the rockers to be just right 1/2 turn preload. The poly-locks have a small allen head lock screw in the top once adjustment is final. Instead of the stock non-adjustable style. My engine oils through the pushrods, so not the same as early models. But my point is the poly-locks were an easy way to get optimum lifter preload adjustment. FWIW, I adjusted them hot and running, loosen until clicking, then tighten to zero lash and no click, then 1/2 turn more. Yes it can/does make a little oil splash mess, but the engine runs very smooth with proper adjustment.
James my Father-in-Law and I are rebuilding his 347 and are planning the upgrade to the sbc summit roller tip rockers. My question is in regards to the camshaft. We had the summit K2800 picked out but then read about confirming that the #2 and #4 journals are cross drilled for the rocker arm stud oiling and apparently it is not. We are wondering if since we will be oiling through the pushrods to the rocker arms if it will matter if we use this camshaft? I'm assuming that oil will just not be fed to the rocker arm studs. Thanks in advance for your feedback.
You have it correct, you can run any camshaft if you are using pushrod oiling and modern rockers. with the heads off it would be a good idea to tap a pipe plug in the oil holes (one on each deck) to block any flow to the heads. make sure the plug is below the deck surface. also if you are using the original studs it would be wise to drill and pin the studs too.
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