Rocker Arm Bolts TTY?

[Number4]

Reading the Haynes manual, it's says torque to 24 ft lbs (2 turns a bolt, I know) but then it says "Tighten an additional 90 degrees." That sounds like torque to yield to me.

Yet it doesn't say not to reuse the bolts. Granted, 24 ft lbs and an addt'l 90 degrees probably isn't that much torque for bolts this size.

What have you done?

 

[natenkiki2004]

I re-used mine. I have the factory service manual and I'm pretty sure I used that during the process, no mention of them being TTY bolts (but it did mention the harmonic balancer pulley bolt is TTY and has to be replaced). I'll tell ya though, the previous owner did mine and I doubt he bought new bolts, they were stuck in there good.

 

[SuperKirby]

I reused mine. After torquing them down then going the additional 90, I could have still got more out of them, so I don't think they're TTY.

 

[2stroke]

A lot of times they will have a spec on bolt length for TTY bolts. An example would be head bolts or studs. I'm not sure why you would chance re-using them, but a lot of times you can measure the length and check if the are stretched beyond their limits. On a side note, I heard subaru re-uses all their head bolts. I can't imagine rocker arm bolts being that big of a deal.

 

[FR-425]

It's a metallurgy thing.... Due to the dissimilar metals when you first "snug" down the bolts the firm contact with the cast iron draws heat out of the rocker assembly and so it shrinks a bit. Wack it 90* more to take up the slack.

The final torque is dependent on the ambient temp of the engine at the time of assembly and is therefore not given. The initial torque spec just makes sure you don't over do it, precision torque is not needed in this application (it's just a bracket)

If you over do it though, it will pinch the rocker shaft, or break the aluminum bearing/bracket.

 

[Number4]

Spoke with Ford service dept today. He said that they are not torque to yield. Something about 46 - 50 something foot pounds. I'll test to see what my final torque is following the Haynes manual.

 

[jd4242]

I reuse them all the time