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Old 11-26-2008, 06:50 PM
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Rocker Arm Stud Length - Help - Thread Length

installed new rocker arm studs on my big block chevy. These studs are a bit shorter than the ones I took off (long story - the old studs were probably the wrong length (too long)?

Question: What is the minimum number of threads needed on the stud for the adjusting nut to be secured? There are approximately 7-8 threads exposed after the rocker arm is installed. Is that enough? The old studs were longer by about 1/4" and had more threads exposed.

These are 7/16" x 20 studs I believe. I'm running full roller rockers with a roller cam. These are stock iron - oval port heads.

thanks

Lee
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Old 11-26-2008, 11:47 PM
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That's a good question Lee. I'm not sure of the answer tho'. I'd check with ARP for the best Info. I do know Roller rockers take longer studs. List what parts & heads you're using & they should be able to tell you the length needed.
http://www.arp-bolts.com/Contact/Contact.html
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Old 11-27-2008, 03:32 PM
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That is not enough, call the rocker arm manufacturer to find out the recommended stud length for your application. A good rule of thumb is that there should be 1.5 times the diameter of the stud sticking out of the rocker with pushrod installed.
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Old 11-27-2008, 04:31 PM
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For the stud end depth screwed into the head, the proper dimension is 1 1/2 times the stud diameter. example, a 7/16 diameter stud threads should be 11/16 deep into the head.

For the stud amount sticking out of the rocker nut with the rocker tight/adjusted, 1 1/2 threads is sufficient. Any more is just excess waving in the wind.
Polylocks require specific lengths since the lock hits the top of the stud.

Studs come in various lengths because some rocker arm trunnions are thicker.
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Old 11-27-2008, 05:55 PM
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Lee, Is the set screw flush,above,or below the top of the adjusting nut and how much when the valve is properly set?
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Old 11-28-2008, 06:59 PM
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Quote:
Originally Posted by GMC boogie
Lee, Is the set screw flush,above,or below the top of the adjusting nut and how much when the valve is properly set?
this is getting interesting........................

with the rockers I have now (crane energizer), and the adjusting nut set to specified lash (.018") the top of the set screw is "below" the top of the adjusting nut by 2-3 threads. That tells me the stud is too short.

The studs I have are 1-3/4" overall length from base to tip. I really need a stud that is 1-7/8" length. However the next available size is 2". So that will be too long, and then the jam screw may end up sticking out the top of the adjusting nut by 1-2 threads or so.

Now what?
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Old 11-29-2008, 06:53 AM
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I checked Summit's web site and they have several lengths between 1.75 and 2.00.

The only size in between made by ARP is 1.90...which is just about right.
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