Why am I having trouble torqueing down the rocker arm bolts? Its a 340, original x heads ( have been cleaned and magnafluxed) and I'm using the original bolts. I oil the bolts and start torqueing at a lower torque value and work my way up to 30ft/lbs. I've broken two off in the drivers side head. The other side I cleaned the holes out and used a tap to clean the threads (I was told thats not what you're supposed to do, but I'm at my witts end). I get to 20ft/lbs fine, but when I move onto 30ft/lbs all the bolt does is turn. Any ideas? Am I doing something wrong? Please help, im tired of drilling bolts out.! Thanks
I keep breaking rocker arm bolts, help please!
- Thread starter konrad
- Start date
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DON'T OIL THE BOLTS!!!
Run a tap in the hole for the bolts, then run a die down the bolts so you have clean threads in both the hole and on the bolt.
then run them down DRY.
80% of the torque for a joint is from the friction on the threads. By spraying them with oil, you are reducing the friction greatly. So for the same torque, you are getting much more "clamp" because you are stretching the bolt more per unit of torque with them "wet" vs "dry".
In simple lay-man's terms. By oiling them, you are reducing the friction on the surfaces so much that you're overstretching the bolts (for that torque).
Run a tap in the hole for the bolts, then run a die down the bolts so you have clean threads in both the hole and on the bolt.
then run them down DRY.
80% of the torque for a joint is from the friction on the threads. By spraying them with oil, you are reducing the friction greatly. So for the same torque, you are getting much more "clamp" because you are stretching the bolt more per unit of torque with them "wet" vs "dry".
In simple lay-man's terms. By oiling them, you are reducing the friction on the surfaces so much that you're overstretching the bolts (for that torque).
Where did you find 30#
SB rocker bolts are 17-18 ft/lbs or 200 inch/lbs
SB rocker bolts are 17-18 ft/lbs or 200 inch/lbs
If you found that bogus list that says LA engines have 3/8 bolts for rocker hold downs, look at the bolt and measure... It's a 5/16!!!!!!
That list is another POS that's been around for decades that sites glom and post up. No due diligence, just post it up without verification. Just like the old exhaust manifold listing.
That list is another POS that's been around for decades that sites glom and post up. No due diligence, just post it up without verification. Just like the old exhaust manifold listing.
russhal
Well-Known Member
I looked in my how to build big inch small block. LA heads are 15ft lbs. Magnum 21ft lbs. I wet torque every thing unless the instructions say not to. You're just over torqueing the bolt. Wet torque is a better torque.
There was a typo in some of the original service manuals for that torque for a while. I had one where someone corrected it.
I forgot to check the torque, but still don't recommend oiling the bolts before torquing. Clean the threads with taps and dies and run them dry.
Yup, they will snap with ease.
russhal
Well-Known Member
Wet or dry? Up to you. Arp gives you lube to put on the threads. I don't think a factory bolt 5/16 bolt will take 30 ft lbs dry or wet. The real issue I think is over torque. Nothing wrong with what krazycuda is saying about doing it dry. A lot of aftermarket fasteners give you wet torque and dry torque values. And they can change between lubricants.
CJP4130
Well-Known Member
After snapping off two bolts in my younger days I stopped torqueing the rocker shaft hold down bolts at all. I just tighten them good and snug and run them. Never had a prob with them and drove 60 miles round trip to work everyday for 8 years.
yuph.............
67Dart273
Well-Known Member
Of course it won't. Bolts are bolts. There are all kinds of bolts, grade 2, grade 5 (which is MOST of what is in your average engine) grade 8 and special grades.
So the listing for "any" grade 5 bolt in 5/16 size, with course threads and lubricant is..........................NOT 30ft lbs
http://www.engineershandbook.com/Tables/torque.htm
So the listing for "any" grade 5 bolt in 5/16 size, with course threads and lubricant is..........................NOT 30ft lbs
http://www.engineershandbook.com/Tables/torque.htm
That sounds like a good plan to me.
Yes. I do think that most of the problem is too much torque, I didn't check the torque spec before my first post, but the lubrication on the bolts can get you in trouble also.
Only use it if the bolt manufacturer specifies it and the torque to use with it. I've seen many times where people put oil/lube on a bolt and it throws off the torque spec/requirements.
nm9stheham
Well-Known Member
^^^^ Right, and the ARP bolts and their lube are designed to work together to give a certain higher-than-stock clamping force. So that ARP lube-then-torque process does not transfer to general bolt torquing.
MRL Performance
Well-Known Member
30# for BBM 17# for SBM
d100clubcab
Well-Known Member
How are yall getting broken off rocker bolts removed from the head?
I used that old fsm that said 30lbs
I used that old fsm that said 30lbs
d100clubcab
Well-Known Member
Hmmmmm
This MIGHT work!
I immediately thought of drilling a pilot hole then using those reverse drill bits or worse sectioning it and breaking out the chisel
You can probably get them right out with a small center punch tapping on the bolt end in a counter clockwise direction. The only thing that holds the bolts tight is the head of the bolt tightening down. It's not like the bolts are bottomed in the holes. They should back right out with little effort.
i tried the "bolt-out" reverse drill bits with no success and I didn't want to keep drilling for fear of doing serious damage, so I took the head to a machine shop. They couldn't get the broken bolt out either, so they sent it to another machine shop with a "edm machine" which uses electric spark that basically melt the bolt to be removed. It was an expensive mistake.
MyMopar has a list of SBM torque specs and it say 30 foot pounds.
MyMopar.com
When I was torquing down my rocker arms, it just "felt" wrong....I ditched the torque wrench and did it by feel. I was sure it would have snapped if i had gone to 30.
Jeff
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One of the best tricks that I learned in my years of wrenching in the rust belt is this - I have used all types and styles of easy outs including Snap-on, MAC, Cornwell, etc . All are pretty expensive and not covered for breakage either. Center punch the broken stud as close as possible to center ( I really like the automatic ones ) use a 1/8 drill bit( you can pick up the high speed double ended ones at the parts store for not much money) drill all of the way through the broken bolt ,soak it with PB blaster, tap in a quality t-15 Torx bit (like Snap-on)until it bottoms out, then use a 1/4 in socket and ratchet to rock it back and forth. Sometimes it has enough bite, but if it spins move up to a T-20. The best part is if the Torx bit breaks simply use a 1/8 punch to knock the broken piece out the other end so you can drill the broken bolt out if need be without the hardened broken bit causing issues. Best of all is the Torx bit is covered under warranty.
AWSOME tip!
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