2F connecting rod torque 100 ft. lbs? (1 Viewer)

[dmaddox]

According to the 2F engine FSM,

You apply plastigage, torque to 45-50 ft lbs, remove and inspect plastigage and then when done . . .

. . .torque the nuts on the connecting rod cap to about 100 ft. lbs???

Is that right?

The only reason I doubt is I am inspecting the nuts on all of the other caps and they were about 50-60 ft. lbs.

As I started to torque close to 100 ft. lbs. I was thinking "Man, this feels like a LOT of torque." I put a ton of force, they were clearly tighter than any other connecting rod (of course I know the crank was out before due to .50 bearings) so did the previous builder not torque to 100? 100 seems like a heck-uva lot of torque on those 14mm nuts.

thoughts?

 

[MtnTrucker]

Are you talking about the main bearing caps or the rod bearings? Rod bearings are no where close to 100 ft lbs of torque. According to the Haynes manual they should be set to 45 ft lbs.

Haynes Manual Torque Specs
Engine Section

Cylinder Head 90 f/lb
Main Bearing Cap 1st 2nd 3rd 100 f/lb
Main Bearing Cap Rear 85 f/lb
Oil Pan 7 f/lb
Oil Pump 10 f/lb
Rocker Support
10mm 28 f/lb
8mm 18 f/lb
F Model Manifold 18 f/lb
2F Model Manifold 28 f/lb
Flywheel 47 f/lb
Crankshaft Pulley 130 f/lb
Camshaft Thrust Plate 10 f/lb
Connecting Rod Bearing Cap 45 f/lb
Piston Pin 45 f/lb

 

[dmaddox]

Thank you for the clarification, I am glad I asked.

I tightened one of them up to about 80 ft. lbs. but I have loosened it and have set it to 45 ft. lbs. Do you think it's going to be ok, or should I get a new nut?

 

[PatFJ40]

The nut won't be the problem. The stud is stretched out though. I would like to say that you should be ok since the force on the rod is downward, but I don't think I would chance it. If there is anyway to replace the stud it would be CHEAP insurance.

 

[Fast Eddy]

The nut won't be the problem. The stud is stretched out though. I would like to say that you should be ok since the force on the rod is downward, but I don't think I would chance it. If there is anyway to replace the stud it would be CHEAP insurance.

Steel is malleable. If it didn't break when you torqued it, and a new nut screws onto it, it will be fine, IMO. I've never seen a stud break in that location. There's not that much force on it.

 

[FJforty]

I think you are OK. Does the manual really say that?

 

[Poser]

Steel is malleable. If it didn't break when you torqued it, and a new nut screws onto it, it will be fine, IMO. I've never seen a stud break in that location. There's not that much force on it.

Huh?

You have not ever seen a connecting rod bolt fail and tear up an engine?


The connecting rod bolts are the 'weak link' in the bottom end of a Land Cruiser engine if you look past the four main bearing set up.

 

[dmaddox]

I can never tell if Poser is being sarcastic, or actually posting a legitimate remark. (No offense).

I admittedly made the mistake of having the FSM laying open and reading the next step after it gives the clearances for the connecting rod bearing, it moves onto the main bearings. I made the mistake - and I am just verifying that I didn't crap up the system.

Like I said, I set my wrench to 100ft. lbs but never did get there. I am "guessing" that after about 70-80 pounds or so, I stopped.

I had 4 threads exposed on the stud, whereas all of the others only had 3 threads exposed. This is when I quickly thought I had better stop and re-read the instructions.

If it is possible that the stud is going to snap due to me over torquing - I'll just use another out of my parts bin.

HOWEVER - if it is highly unlikely that I did any damage - I'll just leave it in there.

thanks!!!

 

[Poser]

If it is possible that the stud is going to snap due to me over torquing - I'll just use another out of my parts bin.

That would be the safe bet.




Connecting rod bolts stretch and fail at higher RPMs; this is not uncommon in old engines. The 409 Chevy could not handle sustained high RPMs because the connecting rod bolts would stretch and the bottom end would come apart. The Land Cruiser engine is the same. That is why folks that intend to spin this engine up replace the factory connecting rod bolts with something that is not going to stretch and fail like old factory hardware can.

 

[dmaddox]

Thanks man - I appreciate it!

 

[CruiserShel]

That would be the safe bet.




Connecting rod bolts stretch and fail at higher RPMs; this is not uncommon in old engines. The 409 Chevy could not handle sustained high RPMs because the connecting rod bolts would stretch and the bottom end would come apart. The Land Cruiser engine is the same. That is why folks that intend to spin this engine up replace the factory connecting rod bolts with something that is not going to stretch and fail like old factory hardware can.

I am getting ready to rebuild my 2F. I don't plan on spinning the engine any faster than normal, but I would like to replace the connecting rod bolts and main bearing bolts while I'm in there. From my GM V8 building in the past I've always used ARP fasteners for such critical bolts, but I'm having trouble finding them for this application. Poser, what bolts do you know of guys going with instead of old factory hardware? Thanks!

 

[Poser]

I am assembling a 1980 2F and using the stock rod bolts and mains that came with the engine.

I am not aware of any after market main bearing bolts for this application, but I have not spent much time looking either.

Connecting rod bolts, IIRC, you can use big block chevy connecting rod bolts after you modify the connecting rod so they sit properly in the rod.

I have not ever done this, as I have not ever had the plans to spin one of these engines beyond the 4500 mark for any sustained length of time.

It is an old tractor engine.

 

[CruiserShel]

Poser, thanks for the reply. Do you have any ideas on new head bolts? I'm just used to replacing all of the above bolts during a rebuild since they stretch and age. Again, it's not really because of any performance gains or high RPM usage, but it just makes sense to me to replace them during a rebuild. But this is my first 2F rebuild, so I'm learning.

 

[Poser]

You can find head bolts...but you will choke when you see the price.


Unless there is visible corrosion on the shank/thread area, I run the old ones.

These are not torque to yield or torque turn fasteners dealing with the typical consumable fastener system of late model vehicles, but rather, designed so that you can use them again.

 

[Bluegrass40]

I think you are OK. Does the manual really say that?

I know these posts are really old, but for the sake of clarity, the fsm does not state a spec for 100 ftlb for the connecting rod cap nuts. Here is a screen shot from the manual. I think he op may be getting the connecting rod and main caps confused. The manual I referenced has the connecting rod caps at 45 and the mains at 100. I am showing the section where the plasti gauge is used and at final assembly.