Rocker Arm Swap - Pontiac GTO Forum
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post #1 of 16 (permalink) Old 04-25-2018, 07:53 AM Thread Starter
 
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Rocker Arm Swap

Hi GTOForum,

I am a new member and posted in the intro forum yesterday. I am glad to finally have joined a GTO community after having my car since just before turning 16. Wow, that is almost 20 years now! I am starting to get the itch to spend some spare time (like I have any) on the GTO and getting it tuned and back in good shape. It still runs pretty strong but has always had a hard time idling when cold and some other odds and ends. I know there are a ton of articles on carburetors and tune ups and I have already started going through those.

My question here that I could not find searching. I have had a set of Crane Gold Race Rockers brand new and sitting in the box for probably 12-15 years at this point. They are part#28755-16. I am fairly certain, but it has been a while, that I already have the screw in studs on my 62 heads. This is from what I remember when we swapped the cam. I remember putting the stock rocker arms back on because it was all I had at the time. Is it worth changing to the gold racer rockers?

Thanks!
Nick
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post #2 of 16 (permalink) Old 04-25-2018, 02:48 PM
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Hey Nick, Being full rollers they'll reduce friction losses which will free up some power. If your heads still have the factory Pontiac bottleneck studs you'll have to change them out for BBC style 7/16 studs. If they didn't come with their own lock nuts, then you'll need those also. I'm not familiar with these particular rockers so I can't offer an opinion with regard to their durability or quality however.

In general: Bigger studs are better. Having positive adjustment is better. Having full roller rockers is better. The only unknowns in my mind are quality, and if they'll fit with your valve covers (if you're running and want to keep factory covers).

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post #3 of 16 (permalink) Old 04-27-2018, 07:21 AM Thread Starter
 
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Thanks for your input! I am far from stock appearance and am not interested in trying to maintain it so no concerns there. These do come with the lock nuts. I guess the main unknown is I cannot remember for absolute sure if I have the bottleneck studs or if they had already been replaced. I guess that will be the deciding factor for me. Easy enough to find out when I pull one of the leaky valve covers off.

On a side note, I went out to the garage yesterday with a few spare minutes to try out a borescope that I had purchased. When I raised the car cover from the hood a snake was coiled up right between the scoops. That gave me the jitters for a little bit but still played with the borescope once I evicted the squatter.

Can anyone speak to the quality of these roller rockers?

Nick
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post #4 of 16 (permalink) Old 05-08-2018, 09:21 AM Thread Starter
 
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I finally got my car out and where I could tinker. I did multiple things but sticking to the topic of my thread here I took some pics under the valve cover.

I am a little timid to remove a rocker arm to investigate further. Do I have to do that to determine what studs I have or is it possible to tell from these pics?

Thanks!
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post #5 of 16 (permalink) Old 05-08-2018, 03:44 PM
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Can't tell for certain from the photos which rocker studs you have, but those are adjustable poly-lock nuts you have there. That means you have the ability to positively adjust your lifters.

In order to get a positive ID on the studs, you will have to remove one and see what the stud looks like. If the threads at the top are the same size as the rest of the stud body below the threads, then you have 7/16" "BBC style" studs --- and that's good. If the threads on the top of the stud are slightly smaller than the stud body and you can see a definite shoulder where the stud necks down to the smaller thead size where the threads begin, then you have the factory style Pontiac bottleneck studs.

I assume you're running hydraulic lifters? If so then you don't have to get perfect on the adjustment. What you can do is take a Sharpie and make a mark on the rocker nut and a second corresponding mark in line with that mark somewhere on the head that lines up with it. Put a wrench on the outside hex head of the rocker nut to hold it so that it can't move while using a hex key wrench on the inner lock nut to loosen it off. Then, carefully remove the rocker nut wile counting the number of turns it takes to get it off. When you're ready to reinstall it, screw it back down exactly that many turns until your marks are "not quite" lined up again, then tighten down the inner lock nut snugly, and finally use a wrench to turn the outside of the nut until your marks line up. This gets the inner lock tighter than can be done using the hex key alone and makes sure it'll stay put.

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post #6 of 16 (permalink) Old 05-09-2018, 07:20 AM Thread Starter
 
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Great advice and much appreciated! That is exactly what I needed to get me in there and pull the rocker arm off. I will do that in the next couple of nights and report back.

Thanks again!
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post #7 of 16 (permalink) Old 05-14-2018, 06:34 PM Thread Starter
 
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They are 7/16"! No shoulder and I measured them to be safe. Now I have to decide if I want to change them now or when I pull the motor out to clean it all up. Probably now;-)
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1970 GTO, 461 cid
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post #8 of 16 (permalink) Old 05-15-2018, 04:58 PM
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Awesome - you've got 'the good stuff'. No need to change them unless you make other changes and it causes you to need different lengths. This means your valve train is already fully adjustable, and if you want to install those Crane rockers you have, you're good to go. All you'll need to do is swap them out and re-adjust all your lifter preloads. Google tells me those rockers are stock 1.5:1 ratio, so you shouldn't have to worry about needing to clearance the pushrod passages in the heads or need new pushrods. Keep in mind though, that the pushrods you have will have 'worn in' to the rockers you have so if you swap them, they'll have to do that again - which means that after you've run them "awhile" - a few hundred miles or so, you'll want to re-check all the adjustments.

Those full roller rockers equate to free power by reducing friction losses.

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post #9 of 16 (permalink) Old 05-15-2018, 08:27 PM Thread Starter
 
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Thanks for all the help and advice. It is really appreciated. I planned to use this procedure to adjust the new rockers. Sound fine?

Pontiac Rocker Arm Adjustment

Nick
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post #10 of 16 (permalink) Old 05-16-2018, 12:14 PM
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Quote:
Originally Posted by nrc17gto View Post
Thanks for all the help and advice. It is really appreciated. I planned to use this procedure to adjust the new rockers. Sound fine?

Pontiac Rocker Arm Adjustment

Nick
Yep, that process will work fine - as long as the cam you have is relatively close to being stock. Personally, I prefer to adjust valves one at a time, in firing order sequence in order to make double doggone sure that each one gets adjusted while its lifter is on the base circle of the cam. I turn the engine over by hand until I see exhaust valve #1 just beginning to open, then I adjust the INTAKE valve on #1 . Turn the engine over a little more (about 90 degrees) until I see exhaust #8 starting to open then adjust intake #8 ---- etc. 1 8 4 3 6 5 7 2. Starting over on the exhaust valves, turn the engine over until I see intake #1 just beginning to CLOSE.. and adjust exhaust #1 ---- and so on. This process is guaranteed to be right no matter how rowdy the cam is or how much duration it has. But, for stock or close to stock --- the process you found is just as good and doesn't take as long.

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