3.4camaro

iTrader: (1)

Ever since my h/c swap in June, I've broken TWO different rocker arm bolts. One about a week after the swap, and one last week. These are Harland Sharp roller rockers and the bolts are the Grade 12.9 that come with them.

Loc-tite(Red)
Torque to 22 ft/lbs
Turn the engine over twice
Re-torque to 22 ft/lbs

Am I doing anything wrong?

Randy WS6

iTrader: (69)

Check your push rod length , it could be coil bind

3.4camaro

iTrader: (1)

The pushrods are 7.500 from trickflow. They came with my heads, and I was instructed to use Harland Sharp rockers.

bjamick

iTrader: (31)

What about your lifters? Are they the stockers? I would say you might need to get a pushrod length checker just to make sure.

99blancoSS

iTrader: (115)

Did they know what cam you were running? You should not be braking those bolts !

bczee

iTrader: (12)

What springs are you using ?... check for coil binding.

Randy WS6

iTrader: (69)

But what is the (Base Circle) of your cam shaft ? ,and what thickness is your head gaskets, That must be known before push rods are install, (You must use a push rod checker).That is a long push rod 7.500" for a LS1 , The Trick Flow heads must have a very tall deck height.

3.4camaro

iTrader: (1)

I bought the heads assembled from TEA, as well as the TFS stage III cam, 228/230. I have caddy lifters. They knew all my parts, my Cometic .040" gaskets and assured me everything would work as planned. Everything came together nicely, but I've broken 2 rocker arm bolts on 2 different cylinders using 2 different rocker arms. I think when I re-install I'll go lighter on the torque spec, perhaps 20 ft/lbs. This might keep the bolts away from their failure point.

7.500" is quite long for an LS1 motor, but TFS heads have a change in valve angle and a 3/4" deck height, so that's probably where the length on the pushrods goes.

Old SStroker

If you are breaking 8mm (?) bolts @ 22 ft-lb, and they are good bolts, it's the working loads on them that are breaking them, not the install torque. Reducing the install torque reduces the clamping load and may make the problem worse.

Where are they failing? Near where they thread into the head? In the threaded area? or ??

What kind of a failure? Tension? Bending? Do you have pics of the broken bolts and the part still in the head that you can post?

You really need to use a checking pushrod and determine the CORRECT pushrod length for your installation. If the PR length is incorect it could be the cause of the loads which are breaking the bolts.

Don't expect a different outcome by just putting more bolts in at the same or slightly reduced install torque. OK, there is a slight possibility they could be bad bolts, or if they were machined, and failed in the machined area it could be do to the machining, but that is unlikely. If I recall the Sharp design correctly there are stands which the bolts go thru into the head. This leads me to suspect that bending loads are the culprit.

Jon

vettenuts

iTrader: (4)

How are you installing, what procedure?


If you are following the LS1howto or GM procedure, it is incorrect for a tandem shaft rocker setup and as stated by Old Sstroker your bolt preload may be way off resulting in bending loads in the bolts and fatigue, clearly a load they are not supposed to be subjected to if installed correctly.

3.4camaro

iTrader: (1)

I've been torquing to 22 ftlbs just like it said on the box of rockers.

EDIT- Mike I'll be available after 3pm central to speak with you.

vettenuts

iTrader: (4)

Let me clarify, are you installing all the rockers at one time or are you installing each cylinder as the piston is the the top of its firing stroke such that the both lifters are on the base circle?

3.4camaro

iTrader: (1)

No, I was not installing one at a time. Both rockers were tightened down in increments so the cross shaft was not stressed or bent.

Old SStroker

That's exactly where bending loads would break the attaching bolt. If you were to thread the bolt into the head without the rocker or rocker stand attached and strike the head of the bolt with a hammer ("sledge" or otherwise ) perpendicular to the bolt's axis it would fail just as yours did.

Why are you getting strong bending loads? I still think that an improper pushrod length may be the most likely culprit. The HS website for these rockers says, "These non-adjustable rockers are designed to the factory specs. If you change camshafts or machine the heads, you will have to correct your pushrod length. Always check before installing."

As far as I can tell from your posts, you did not check for correct pushrod length. IMO, you really need to do that before you run the engine. If it is incorrect, get the right length pushrods and replace all of the rocker arm bolts.

At least that's what I would do.

[EDIT] What I would really do is use stock rockers...perhaps with upgraded trunnion bearings. I like the stock design for strength, lightness and low moment of inertia.


Good luck.


Jon

3.4camaro

iTrader: (1)

Thanks Jon. I'll talk to TEA and look into getting a pushrod length checker.