Gn1 heads shaft mount rocker torque specs ?

[434nova]

I am putting my gn1 shaft rockers back on my gn1 heads , what is the torque specs for the 3 bolts that holds the shafts to the heads ? Thanks

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[bison]

25 foot-pounds is adequate. The most important thing is to use the longest possible bolt to get the most engagement. A stud with a nut would be nice but trying to find the correct length quality stud is problematic would be nice to have the top of the stud fine thread


BPE2013@hotmail.com

 

[434nova]

Should I use any thread sealer or loctite on the bolts ?

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[turbodave231]

You don't need Loctite or sealer. Oil the bolt. Be careful, the helicoils will pull out easy.

I have searched all over for a stud that will work in this application. I ended up buying 5/16 Grade 8 bolts 3 inches long. The bolts are threaded the entire length and are 180,000 psi tensile strength. I cut off the heads and ground the ends nice and square. I bought 12 point nuts to finish the package. The same homemade studs will work on stock heads/shafts too. All these parts can be bought from McMaster Carr.

 

[jpwalt1987]

Make sure the helicoils go all the way to the bottom of the hole.

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[turbodave231]

The helicoils that champion install do not go to the bottom of the hole. They should!!!


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[turbodave231]

A couple of pics

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[jpwalt1987]

The helicoils that champion install do not go to the bottom of the hole. They should!!!


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I broke a rocker pedestal off because of this. PITA

http://www.turbobuick.com/forums/threads/broken-gn1-rocker-stand.386992/

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[turbodave231]

A broken pedestal sucks!! Was there porosity in the head? how did you fix it?

 

[jpwalt1987]

No porosity. The helicoil didnt go deep enough into the head. The pedestal broke where the helicoil ended. To fix it I pulled the head and brought to a local machinist. He used a new rocker shaft to locate the broken piece of aluminum onto the head then tack welded it on all sides. After it was secured he ground away aluminum all the way to the bolt hole on one side. He then back filled it by welding from the inside out. He did this all the way around so it is a solid piece. Rebored the hole and tapped for a .975 long helicoil. Pictures are in the above link but yiu have to open the link in a web browser, not the mobile app.

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[Jerryl]

Years ago, I purchased rocker studs from TA. They are about 1/4" to long for stock vc's, so i never used them. Still in a box somewhere along with some other junk.

 

[turbodave231]

Jeremy,

Sounds like your machinist did you right. I'm not sure why Tom doesn't install the proper length heli-coils. He taps the holes to the bottom, but uses a short insert.

Personally I like Timeserts for thread repair. The full body on the insert make it way stronger that an equivalent helicoil.

 

[jpwalt1987]

Jeremy,

Sounds like your machinist did you right. I'm not sure why Tom doesn't install the proper length heli-coils. He taps the holes to the bottom, but uses a short insert.

Personally I like Timeserts for thread repair. The full body on the insert make it way stronger that an equivalent helicoil.

I called Tom at the time it happened. He wasn't sure why such a short helicoil was used. There were a few different lengths installed so I think they just used what was on hand. My machinist does all kinds of crazy repairs that no one else can. All out of his house at that!! Timeserts didnt have a long enough insert at the time. It has worked great. PAC 1203 springs and .540 lift. Accidentally hit 6900 rpm in the burnout box and all is still good.

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[87geeinn]

ARP does have a stud kit. You can see mine in the video that I posted in the thread above this one called "excessive valve guide clearance." Got them from TA Performance years ago. Last item on the list.

 

[turbodave231]

I wish I had known that 2 months ago!!

That stud must be a custom part made by ARP for TA. I called ARP and talked to an engineer. He told me that a custom (EXPENSIVE) part was my only alternative. If you're not a big race team, they want to bend you over!!