Hello All - My 1969 Firebird went in the shop (initially low priority) over 7 months ago. The shop decided to get it back together installing new cam, rocker arms, and lifters. The shop noticed that some of the rocker arm studs were messed up and were going to replace them, but discovered the studs are screw-on instead of press-on studs. The Firebird was originally presented as a 400, but I discovered right before buying the car that the motor was a 1965 389ci out of a Bonneville class car. The shop says the casting numbers on the heads seem to be consistent with the motor, but they just cannot find the right screw-on studs to put the motor back together. For lack of any other ideas, they are going to just order in some big block Chevy screw-on studs and see if they work. Does anyone have any idea why the shop may be having a rough time? Are there Pontiac options that may have been used in the day that they just don't know about? Thanks in advance for any tips.
Chevy studs may not work right. Butler sells several sizes of screw in studs. I'd suggest calling them. Measure the ones you have and see if Butler has the same ones. I had some heads that were machined for screw in studs but the studs were probably chevy studs and needed washers under the nuts to allow them to be snugged down and adjusted properly. I used some Lowes grade 8 washers that ended up being noisy because they were probably too big. Butler also sells special washers.
No sure what year Pontiac started using screw in studs, but stock BBC will work with standard spring height. Proby have a couple used Pontiac sets stored here somewhere. Just pay shipping.
My garage thinks that for some reason they took some of the press-on studs, cut threads on them, and made them work. Thanks for the info guys, I think I will see if the garage has tried Butler yet, if that doesn't work I will be back in touch with you Region Warrior.
Couple of thoughts. You sure the heads off the 389 or are they off a different engine? Maybe the heads were using hollow studs that oiled through the studs not the push rods. I don't think any of the production heads had screw in studs in 1965, but who knows. Could be the studs were pulling out and someone tapped them for screw in. If some of the studs are still press in and some screw in I would think you'd want to have the shop tap the whole works for screw in. The standard Pontiac rocker stud since the mid fifties for hydraulic lifters had a shoulder on them just below the threads, the nuts have a matching bevel. The nuts were just run down to the shoulder and torqued to 20 foot pounds to hold the rockers on. No need to adjust the lifter pre-load. You can use big block Chebby studs which have straight shafts with no taper, but you will have to use some locking nuts and set the pre load, that's no big deal. If your machine shop is going to put on Chebby style it will have to be Big block studs as they are shorter, to clear the rocker covers. One can use the small block ones and cut then down to the right height, but may as well use the correct length from the start Just my opinion, I'm not an expert. .
Thanks Bluebird428! Interesting discussion there. My garage thinks some shade tree mechanic did it back in the day for some reason (he probably thought it was good), but it is really causing me a headache. As far as the heads go, all I have to go on is what the garage researched. They thought the numbers were consistent with the rest of the motor. Thanks for the tip on the locking nuts, luckily the rocker arms that I bought (that we thought would slip right on) have the locking nuts on them. It's been an eternity since I dropped the it off, just hoping they can find something off the shelf from Butler.
Give us the numbers on the motor and the heads and we can tell you what you’ve got. At least the numbers/letters on the center exhaust port on the heads.
Looks like 389 head and block to me, date code on head looks like 1964 for a 1965 389. Do you have a 75 or 76 or 77 or ? cast on the center exhaust ports?
The block is a 389 but I can't make out a date code. As long s it is 1964 or later it should have pushrod oiling and you wouldn't have to worry about hollow studs.
