Grade 5 or Grade 8 for Rocker Covers?

[GIBSON]

S&S sends you 16 plain grade 8 bolts for your rocker covers to attach to their super stock shovel heads (5/16-18 x 2 1/2) and 2 Grade 5 bolts (5/16-18 x 1 1/2).
They are plain steel and discolored in less than 1000 miles. Anyways, since my HD rocker covers are now chromed, I picked up 18 beautiful replacements from Diamond Engineering. Come to find out, the whole load is Grade 5 hardness.
Do you think these will do the job for me without breaking apart?

[plongson]

5/16" grade 5 is good for 120,000 psi and about 20lbs torque to start. 5/16 grade 8 is 150,000lbs and about 30lbs torque to start. Torque depends greatly on how clean the threads are and lubrication.

What does the HD manual call for torque on these fasteners? If its just the top cover and not the heads themselves, G5 is probably just fine.

[claydbal]

grade 5 will work great. torque is in inch pounds.

[motrhd]

Yup

[plongson]

Actually the torque is in Foot/Pounds for this grade of 5/16" screws. A 1/4"-20 socket head, for instance, runs between 90 to 120 INCH pounds.

NONE THE LESS...ALWAYS USE CAUTION AND DESCRESION WHEN TIGHTING ALL YOUR FASTENERS!

http://www.raskcycle.com/techtip/webdoc14.html

[GIBSON]

Service manual 1970-'77 says 15 FT LBS.

Thanks for yer helps and...

MERRY CHRISTMAS!!!!!

[plongson]

One thing you always have to consider when thinking about "How Tight" is..."What is it screwing into". A G8 screw going into a G8 nut is designed to take the prescribed amount of torque from the tables.

On the other hand, a G8 screw going into a soft metal (aluminum) will pull out the threads long before it stresses the fastener. Many of the HD torque specs assume G5 socket head or Torx head going in soft aluminum are low to protect the female threads.

[GIBSON]

Finally; I forgot to mention that the bolts I purchased from Diamond Engineering are stainlees steel polished (grade 5). Some say that the stainless steel bolts are the weakest.
What say you???
Furthermore I notice that torque values change when using dry or wet. Should lock-tite be used at all???

[77Ironhead]

I don't think the OE studs @ 15 Lbs. is the same as a 5/16 Bolt supplied by S&S. As I recall the OE studs were 5/16 threads and the un-threaded portion looked more like a 1/4 - they were designed to stretch as the rocker box expanded so as to not over compress the fiber gasket . With newer type gasket materials and a 5/16 bolt I would use the spec supplied by S&S.

[Dr.Hess]

Well, in my opinion, be careful with stainless and aluminum. The aluminum looses every time. Not that you can't do it, just be careful. Use plenty of Neverseize or Locktite. Stainless bolts are generally a little under grade 5 or so, if I recall. Still plenty strong for holding a rocker box on an aluminum head.

15 foot pounds = 180 inch pounds.

[plongson]

One thing that I have learned over the years from my 40 or so years the maintenance industry, is that you have to be careful or at least cognizant, that T304 and T316 stainless will actually work harden in high stress applications. Work Harden=stress cracks=failure. Just be aware...

For instance, I would never use say 1/2" SS bolts for a trailer hitch. Pay the man and go G8. These are extreme cases and SS screws are just fine for what they are designed for.

[1711tab]

Originally Posted by GIBSON

S&S sends you 16 plain grade 8 bolts for your rocker covers to attach to their super stock shovel heads (5/16-18 x 2 1/2) and 2 Grade 5 bolts (5/16-18 x 1 1/2).
They are plain steel and discolored in less than 1000 miles. Anyways, since my HD rocker covers are now chromed, I picked up 18 beautiful replacements from Diamond Engineering. Come to find out, the whole load is Grade 5 hardness.
Do you think these will do the job for me without breaking apart?

Grade 5 is more than enough for this application... Your compressing a gasket so it doesn't leak...

[ruben123]

Great summation, i always use grade eight..but you do have to be on it when you screw into aluminum..
Good summation..
thanks

[DD Slider]

Originally Posted by Dr.Hess

Well, in my opinion, be careful with stainless and aluminum. The aluminum looses every time. Not that you can't do it, just be careful. Use plenty of Neverseize or Locktite. Stainless bolts are generally a little under grade 5 or so, if I recall. Still plenty strong for holding a rocker box on an aluminum head.

15 foot pounds = 180 inch pounds.

I heard loctite is not to be used in Aluminum...?

[route66paul]

don't think about using stainless into the head or any hot spots in thr aluminum. Even with never seize, it can still gall. There is a particuliar chemical reaction here. if you do, use a lot of never seize or a high temp thread compound