Conrod bolts

[millosman]

Hello everyone,

I've got my FJ motor in pieces at the moment for a rebuild.
My Haines manual says to tighten the Conrod bolts in one continuous movement without stopping until the correct torque setting is reached.
It seems to me to go against the grain by tightening one bolt up completely whilst the other is slack.

Can anyone advise on the correct approach please?

Many thanks
Andy.

[Old Rider]

Hello everyone,

I've got my FJ motor in pieces at the moment for a rebuild.
My Haines manual says to tighten the Conrod bolts in one continuous movement without stopping until the correct torque setting is reached.
It seems to me to go against the grain by tightening one bolt up completely whilst the other is slack.

Can anyone advise on the correct approach please?

Many thanks
Andy.

The manual says to apply continuous torque from 3.0 to 3.6 m.kg (36 newton) so you can first torque to 30 NM then thigten to 36NM in a continuous motion and dont forget to apply moly disulfide grease on the treads.
I replaced my bolts when i did mine. because when i tryed to torque to 36 NM the bolts just stretched so i could not reach 36 NM before bolt snapped.

[millosman]

Thank you Old Rider. That's just what I needed to know.
I have read about these bolts stretching. Without knowing their original length I guess there's no way of knowing how much they've stretched already.
Think I'll price up some new ones to be in the safe side.
Thanks again,
Andy

[Troyskie]

G'day fellas,

Millosman, I'm in the middle of the same thing. I have some new ones on hand as I'd followed Oldrider's EXCELLENT pictorial project write up http://www.fjowners.com/index.php?topic=18143.0

Here's a pic of one of the new con rod bolts on the verniers...

[JMR]

APE used to sell replacement ARP bolts and nuts for the FJ....much better than stock pieces. You could call them about them.

[racerrad8]

Andy, I torque my rod bolts using the following procedure.

I lube the shank of the bolts with oil where they pass through the rod. I use ARP thread lubricant on the threads and underside of the flange nut to ensure proper & consistent torque values. I torque to 15 ft lbs on each rod bod first. I check for smooth rotation of the crank.

I then torque to 25 ft lbs using a slow & smooth application; never twist fast or jerk the torque wrench. I again check for smooth rotation of the rod on the crank. I use Clevite 77 assembly lube on my engine builds.

I only use beam style torque wrenches to ensure proper torque.

Here's a pic of one of the new con rod bolts on the verniers...

Please do not use measurements of the bolts as any form of criteria is the bolt is good or bad. The bolts are not machined to be used with a stretch gauge. The threads are rolled and the tip of the bolt is very inconsistent. The Y on the head can also vary significantly on height.

Proper torque is how the bolts are designed to be used.

APE used to sell replacement ARP bolts and nuts for the FJ....much better than stock pieces. You could call them about them.

The ARP bolt were for the FJ, but they were not a direct replacement. The shoulder of the bolt is larger than stock and requires the rod to be bored or reamed to get the bolts to fit. I only used the ARP bolts a few times and frankly they were not worth the investment. So, I quit using them back in about 97'-98'

The stock bolt is fine and used in 1000's of FJ engines powering race cars all over the world. They are not a weak part/spot of the engine.

And finally, in the last 25 years of building this engine, I cannot for the life of me remember a time where I ever had a rod bolt stretch and break while torquing. If the bolt stretches and breaks while torquing, then you have a wrench issue.

Randy - RPM

[millosman]

Thankyou everybody for your advice in this.

I now have a procedure to follow when torquing the conrod bolts thank you.

As the amount of any stretch doesn't necessarily give an indication as to whether a bolt is fit for re-use, then I guess there is no way of knowing this.

So may I ask, does everyone replace the bolts each rebuild, or trust that if a bolt can be torqued successfully to full setting that the bolt must therefore be ok?

Pricing replacements in the UK they're over £50 a set.

Would you replace regardless or re-use?

Thanks
Andy

[racerrad8]

I replace them every time.

When you say 50 a set, is that for all 8 or a set of 2?

And does that included the nuts too?

Randy - RPM

[millosman]

Hi Randy
I've just checked pricing and the bolts are £6.32 each and the nuts  £2.96 each. So £9.28 each set. So more like £75 for a complete set of bolts and nuts.
Not cheap.

Regards.
Andy

[CutterBill]

...If the bolt stretches and breaks while torquing, then you have a wrench issue. 

This. Absolutely...

Hey Randy, just for fun... next time you have some old con-rod bolts, take one and torque it until it (1) noticeably stretches then (2) breaks or strips. Would be interesting to know...
Bill