Rocker Arm Bolt Questions
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Rocker Arm Bolt Questions The stock rocker arm bolts have some kind of red RTV sealant on them where the head meets the trunion (see attached photo). What's the real purpose of this ... is there oil pressure someplace that would warrant sealant?
There was no loctite on the factory bolts and the shop manual does not indicate that loctite is needed.
However, the rocker arm bolt threads were covered with oil when removed, so I'm assuming there is some oil where the bolts screw down into to the head someplace ... maybe that's the reason for the RTV sealant (?).
I'm putting in the Comp Cams trunion kit which has new Allen head rocker arm bolts.
Questions are:
1) Is there a real need for the sealant on the bolt like the factory setup? ... the shop manual says nothing about it.
2) Should the bolt holes be cleaned up so the threads are dry before reassembly? Is so, what's the easiest way? Lubed threads will change the bolt tension when torqued, and I'm assuming the 22 ft-lbs of torque called out in the shop manual is with dry threads. Is it OK to torque these to 22 ft-lbs with oily threads?
3) Are the rocker bolt holes in the head open to something below where they protrude down into the head? The length of the new bolts are ~0.220" shorter when installed than the factory bolts, but I'm curious where the hole goes ... it does not look like a blind hole.
There was no loctite on the factory bolts and the shop manual does not indicate that loctite is needed.
However, the rocker arm bolt threads were covered with oil when removed, so I'm assuming there is some oil where the bolts screw down into to the head someplace ... maybe that's the reason for the RTV sealant (?).
I'm putting in the Comp Cams trunion kit which has new Allen head rocker arm bolts.
Questions are:
1) Is there a real need for the sealant on the bolt like the factory setup? ... the shop manual says nothing about it.
2) Should the bolt holes be cleaned up so the threads are dry before reassembly? Is so, what's the easiest way? Lubed threads will change the bolt tension when torqued, and I'm assuming the 22 ft-lbs of torque called out in the shop manual is with dry threads. Is it OK to torque these to 22 ft-lbs with oily threads?
3) Are the rocker bolt holes in the head open to something below where they protrude down into the head? The length of the new bolts are ~0.220" shorter when installed than the factory bolts, but I'm curious where the hole goes ... it does not look like a blind hole.
Last edited by ZeeOSix; Jul 11, 2011 at 02:04 AM.
See below.
The stock rocker arm bolts have some kind of red RTV sealant on them where the head meets the trunion (see attached photo). What's the real purpose of this ... is there oil pressure someplace that would warrant sealant?
There was no loctite on the factory bolts and the shop manual does not indicate that loctite is needed.
However, the rocker arm bolt threads were covered with oil when removed, so I'm assuming there is some oil where the bolts screw down into to the head someplace ... maybe that's the reason for the RTV sealant (?).
Not sure why it is there but there is no need to seal the threads unless aftermarket or ported heads where the intake bolt will typically break through into the port.
I'm putting in the Comp Cams trunion kit which has new Allen head rocker arm bolts.
Questions are:
1) Is there a real need for the sealant on the bolt like the factory setup? ... the shop manual says nothing about it.
No, unless aftermarket or ported heads.
2) Should the bolt holes be cleaned up so the threads are dry before reassembly? Is so, what's the easiest way? Lubed threads will change the bolt tension when torqued, and I'm assuming the 22 ft-lbs of torque called out in the shop manual is with dry threads. Is it OK to torque these to 22 ft-lbs with oily threads?
Lubed vs. dry will change preload with same torque value by approximately 25%. There is a lot of thread engagement so the increase in preload shouldn't be an issue. My AFR heads are open to the intake port so I use blue loctite and kept the 22 lb-ft even though loctite acts as a lubricant when installed. As far as cleaning, I bought the ARP thread chaser for this purpose. Another tool I use is a pistol cleaning kit from Wal Mart that has circular wire brushes. These come in handy for cleaning bolt holes.
3) Are the rocker bolt holes in the head open to something below where they protrude down into the head? The length of the new bolts are ~0.220" shorter when installed than the factory bolts, but I'm curious where the hole goes ... it does not look like a blind hole.
If the heads are stock the holes should be blind. Does your decrease in length measurement include the unthreaded end on the stock bolts? Also, why not just re-use the stock bolts?
There was no loctite on the factory bolts and the shop manual does not indicate that loctite is needed.
However, the rocker arm bolt threads were covered with oil when removed, so I'm assuming there is some oil where the bolts screw down into to the head someplace ... maybe that's the reason for the RTV sealant (?).
Not sure why it is there but there is no need to seal the threads unless aftermarket or ported heads where the intake bolt will typically break through into the port.
I'm putting in the Comp Cams trunion kit which has new Allen head rocker arm bolts.
Questions are:
1) Is there a real need for the sealant on the bolt like the factory setup? ... the shop manual says nothing about it.
No, unless aftermarket or ported heads.
2) Should the bolt holes be cleaned up so the threads are dry before reassembly? Is so, what's the easiest way? Lubed threads will change the bolt tension when torqued, and I'm assuming the 22 ft-lbs of torque called out in the shop manual is with dry threads. Is it OK to torque these to 22 ft-lbs with oily threads?
Lubed vs. dry will change preload with same torque value by approximately 25%. There is a lot of thread engagement so the increase in preload shouldn't be an issue. My AFR heads are open to the intake port so I use blue loctite and kept the 22 lb-ft even though loctite acts as a lubricant when installed. As far as cleaning, I bought the ARP thread chaser for this purpose. Another tool I use is a pistol cleaning kit from Wal Mart that has circular wire brushes. These come in handy for cleaning bolt holes.
3) Are the rocker bolt holes in the head open to something below where they protrude down into the head? The length of the new bolts are ~0.220" shorter when installed than the factory bolts, but I'm curious where the hole goes ... it does not look like a blind hole.
If the heads are stock the holes should be blind. Does your decrease in length measurement include the unthreaded end on the stock bolts? Also, why not just re-use the stock bolts?
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When I removed the stock rocker arms, there was lots of oil in the rocker arm bolt holes and on the rocker bolts ... maybe the oil filled the holes from the residual oil in the head when I removed the bolts?
I guess I need to stick something down the holes to see if they are blind. If so, I can blow them out with compressed air and clean up the threads before reassembly.
About your bolt length question above. Yes, the new Comp Cams rocker arm bolts are ~0.220" shorter when compared to the OEM bolts (including the un-threaded part of the OEM bolt) when both are assembled into their respective trunion.
If you subtract the un-threaded end of the OEM bolt, then they have about the same length of actual threads protruding from the trunion base. I've got some photos I can post later.
If the OEM bolts are re-used with the new Comp Cams trunions, then they are too long and will probably bottom out in the blind hole.
I measured how many turns the new Comp Cams trunion bolts have when installed with the new trunions, and it was about 12 ~ 13 turns ... so still lots of thread engagement.
Last edited by ZeeOSix; Jul 11, 2011 at 06:33 PM.
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See attached photo for why the Comp Cams Trunion Kit comes with new bolts. You can see that if the OEM bolts are used then the bolt will protrude about 0.10" farther when used in the Comp Cams trunion (middle in photo) ... which will probably bottom out in the hole before the bolt gets tight. Each graduation on the paper is 0.20".
You can see that the amount of threads past the base of the trunion is basically equal between the Comp Cams trunion/bolt combo (left in photo) when compared to the OEM trunion/bolt combo (right in photo).
You can see that the amount of threads past the base of the trunion is basically equal between the Comp Cams trunion/bolt combo (left in photo) when compared to the OEM trunion/bolt combo (right in photo).
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Yeah, the Comp Cams Trunion Kit is a pretty nice upgrade to the stock rocker arms.
I did verify all the rocker arm bolt holes are blind ... you're right on that. So why do you think GM put the red sealant on the base of the OEM bolt heads?
I did verify all the rocker arm bolt holes are blind ... you're right on that. So why do you think GM put the red sealant on the base of the OEM bolt heads?
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Thread Starter
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Joined: Jul 2011
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You could be on to something there. In any case, I see no real need for it so will not use anything on the new rocker bolts. Just plan on cleaning the oil out of the bolt holes and torquing to 22 ft-lbs.
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