73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: sawblade6 on November 13, 2014, 09:31:10 pm
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Just bought a fresh 350 from a builder. Regular rocker arms with non hex Screw in arm studs.
Valves were clacking so thats how I discovered this fiasco. And I called the company too.. still working with them on this.
The poly lock nut grips the stud so tight that doing ANY adjustment causes the stud to break free from the head... so how do I adjust the rocker arm if that stud keeps breaking free!! By the way ALL the studs break free like this.
I scoured the net and found nothing but advice on the hex style arms... my heads are not machined to compensate for the hex as everyone says they have to be.
I have red loctite and the studs ready to go in. They are the regular screw in style with no hex nut. I tried to the double nut trick with 2 poly locks forwards and backwards and both times the stud would back out when I attempted to take off the poly lock.
QUESTIONS ARE AS FOLLOW:
-How do I torque something that does not have a hex on it, or does that 50ft/lbs not apply to my style studs?
-How do I tighten the studs down so they wont budge ever again?
-Is there another style poly lock screw I can use that will work on a STOCK setup?
-Can I screw the studs in too far?
I appreciate your help with this! Im at my wits end on this project.
help please!
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Please post pics that help clarify your dilemma.
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I do not have the ability. I put it all together and am taking it to a shop monday (If i dont get any suggestions here).
Its pretty straight forward and nothing crazy or unordinary.
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Mr. Gasket #1076 are the only studs that I know of that are like that. The 1076 doesn't have much of a flange to seat against the stud boss, so you won't be able to torque them to more than about 15 lbs-ft, if that. I avoid them for that reason. IMO they will work to salvage stock heads originally equipped with press-in studs when the stud holes are oversize, but not really intended for high performance applications.
A "polylock" is a hardened hex-ended nut with an axial set screw that tightens down securely against the end of the rocker stud to prevent the nuts from backing off. From your description, it sounds like you are actually using factory style torque prevailing nuts that have triangularly distorted thread holes which rely on an interference fit and friction to bind the nuts to the studs. When new, they can bite the studs pretty tight.
As long as your motor is a near-stock street application that doesn't use high-pressure valve springs or higher lift than provided by an "RV" cam, you should be able to approach the 'screw-in stud' installation like this:
- Remove the studs and wash their threads and threaded holes using Berryman's B-12, or Brake-Kleen, or starting fluid, followed by thorough drying using clean compressed air.
- Thread two Grade 8, 3/8-24 nuts onto a stud, clamp one of the nuts in a bench vise and tighten the second nut against it. Get it TIGHT, but no more than ~20 lbs-ft.
- Coat the opposite end of the stud with red thread locker (Loctite 271 or Permatex High-Strength Threadlocker 27110).
- Immediately thread the studs into the head and torque to between 10-15 lbs-ft. Carefully loosen the lock nuts so as not to rotate the stud in the head. Since there is very little flange on the studs, avoid the temptation to torque the studs beyond 15 lbs-ft. "Yes" you can overtighten the rocker studs, seat them too deeply and possibly punch through the casting if the stud tightly bottoms in the hole. You may need to experiment a little to develop a workable procedure.
- Similarly install all of the studs then let the thread locker cure for 24 - 30 hours before reassembly; longer if ambient temperature is colder than about 65° F.
- Regarding the torque-prevailing nuts... I'm unaware whether the rocker studs you are using are sufficiently long to actually use polylocks, but under the circumstances would consider Crane, Crower or Comp. If not, then install the torque prevailing nuts onto a sacrificial 3/8-24 threaded rod to help relax the nuts and slightly loosen their fit. Then install the nuts onto the studs using ARP 100-9910 Ultra-Torque compound and adjust the valves. Using the ARP compound once the Loctite has fully cured "should" allow for adjustment w/o nuisance loosening.
Whatever you decide, please let us know the outcome, or whether we can offer further recommendations.
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That is some amazing advice! I looked up the mr gasket parts you mentioned and those are the ones i have.
All my questions have been answered and I am going to get some grade 8 nuts, I think that will help better than the nuts im using on the install. Will post results this weekend.
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Just bear in mind that the recommendations I listed are very specific, down to the products and part numbers where given. You may discover that the studs won't effectively tighten to 10 lbs-ft, let alone 15. Take your time and pay attention to what's occurring as you proceed. Nudge the process, if needed, but don't stray too far from the "recipe." When loosening the two jam nuts, use an open end on the lower nut and a box end or socket on the upper, so the corners of the nuts don't round off before you finish. Best success!
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Can I use the poly lock style but with the set screw in the center? Instead of the stock nut? Or would that not work on a totally stock rocker arm/stud?
Thanks again
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The Crane 99768-16 (http://www.summitracing.com/parts/crn-99768-16/overview/) are made for that purpose. The Crower 86051S-16 (http://www.summitracing.com/parts/cro-86051s-16/overview/) may also work. Verify with Crower (619) 661-6477 or call Summit Racing Technical Assistance (330) 630-0240.
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Called Summit. Crowers won't work but I did purchase the Crane's.
Thank you again. Hopefully they will come in tomorrow.
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just noticed a crack where the studs screw in.... extremely mad and am wondering if I should even run this engine.
Whats the pro/cons of this type of crack and how can I fix it without swapping heads.
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Cracks tend to migrate. The builder should have Magnafluxed the heads before installing them. I wonder if that's why the heads have the cheap screw-in studs? Don't do anything to repair or alter it until you speak with the engine builder. Can you find a way to post a pic?
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i will get a pic soon.
Is there any way that the studs could have damaged the head? Maybe from installing too far? Im trying to spitball some counter points they may make.
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Pic??
Does the crack intersect the stud hole? If the stud was threaded into the hole deep enough to force the collar below the top of the hole, the collar could have wedged the hole outward at the opening, resulting in a crack. If the hole wasn't threaded sufficiently deep using a bottoming tap, the hole could have been wedged outward from the base of the hole, resulting in a crack.
Stud bosses are narrow; there isn't a lot of reinforcement. The narrow flange of the collar should be sufficiently wide to seat against the top of the stud boss, but just barely. That's why you need to be observant and careful when tightening the studs into the head, and not overdo it.
Did you discover the crack during disassembly - was it delivered that way?
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I put RTV in there to show the depth of it.
(http://i232.photobucket.com/albums/ee247/sawblade6/IMG_20141116_104637848_zps693c800c.jpg)
Another cylinder i think #3
(http://i232.photobucket.com/albums/ee247/sawblade6/IMG_20141116_104653570_zps9b229a09.jpg)
Exhaust of #6
(http://i232.photobucket.com/albums/ee247/sawblade6/IMG_20141116_104731894_HDR_zps032508bc.jpg)
Sorry for the delay.
I noticed when I was putting the studs back in. There is no way I over tightened them. I followed your directions to the T. I just think they missed this when they built it.
Im calling them tomorrow to figure out what they are going to do about this.
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In the 2nd and 3rd pics, the collars of the studs sit too deep in the bosses. The narrow flanges of the collars should sit nearly on top of the stud bosses, not well below the surface the way they are. Because stud holes often penetrate the water jackets of heads, the collars are intended to augment sealing against potential coolant leaks by jamming tight against the tops of the bosses. If the bosses were already cracked from the builder, it's a shame you didn't see it during disassembly.
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Via email from Mr. Gasket technical support on 11/20/14, "The Mr Gasket 1076 3/8-24 in. grade 8 studs would be torqued to 34 ft-lb with 30 wt oil."
So, you didn't overtighten the studs at 15 lb-ft. The heads likely were already cracked and delivered that way.
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I appreciate the info.
So I need new heads?
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As previously stated, the rocker stud holes penetrate the water jacket. I know of no repair procedure that I could confidently recommend. Hence, I recommend replacement. Will the engine builder provide any assistance?
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Im still working with them.
I`ll post any updates. thank you for the assistance!