Rocker arm shaft bolt size

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Deleted member 37394

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Can anyone tell me how long the bolts should be that secure the rocker arm shafts to the head?
And are they grade 8 or grade 5? Are there two different lengths?
 
Norm's Cuda said:
Can anyone tell me how long the bolts should be that secure the rocker arm shafts to the head?
And are they grade 8 or grade 5? Are there two different lengths?
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Small block or big block?? Small block are all the same size 2 1/16 x 3/8-16. Big block have 2 longer bolts and are also 3/8-16. I think ive seen them both suggested but since you need no more than 15/20lbs that grade 5 will work best.

Jake
 
I should have said it is a small block. Thank you for the info. Do you know if Edelbrock aluminum heads use longer ones? My are cast iron, I just wondered if they did.
 
Most small blocks are FIVE SIXTEENTHS not 3/8. THERE IS A MISTAKE in the service manual for several years on torque. The book listed torque is for 3/8 NOT 5/16.
 
xLURKxDOGx said:
Small block or big block?? Small block are all the same size 2 1/16 x 3/8-16. Big block have 2 longer bolts and are also 3/8-16. I think ive seen them both suggested but since you need no more than 15/20lbs that grade 5 will work best.

Jake
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Every SB LA factory cylinder head rocker shaft bolts are 5/16. Plenty of busted bolts out there because of messed up info in a service manual. IMO, look at the bolt, see what the diameter is and find a good reference for torque. Grade 5 and grade 8 bolts have different stretch properties, requiring different torque values.
 
5/16 grade 5 is ~13 ft/lbs. Still over 3300 lbs clamping force per bolt. Remember when you torque a bolt, you are stretching it slightly in its recoverable "elastic" zone. Anything more than 13 (for instance) would stretch it beyond its elastic zone where it could not recover and would just permanently stretch and weaken the bolt. Thats why good rod bolts have a dimple on the end so you can chuck up a bolt stretch gauge and use that instead of ft/lbs to get the proper "stretch". 'Snugging' a bolt just somewhat ensures it wont back itself off during normal use, and may be good enough on some apps but every bolt on a motor has a designed torque value that is followed when it is assembled and can be looked up. Some are crazy low like carb studs, barely only enough torque to prevent them from vibrating off, and slant 6 manifold bolts that are designed to let the clamping force allow some sliding of the manifolds themselves
 
crackedback said:
Every SB LA factory cylinder head rocker shaft bolts are 5/16. Plenty of busted bolts out there because of messed up info in a service manual. IMO, look at the bolt, see what the diameter is and find a good reference for torque. Grade 5 and grade 8 bolts have different stretch properties, requiring different torque values.
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Thats what i get for looking it up online. I thought 3/8 was a little big. Thanks for clearing that up for me.

Jake
 
Get some heavy duty rocker shaft studs. You will never have to worry about them again.
 
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