1966 40hp Johnson - Soft Torque on Head Bolt?

[Bay Boater]

Replaced the head on this motor last week (stripped spark plug thread). Pretty straightforward job - EXCEPT...

When I was torquing the far upper left bolt it just came up to 20 ft-lbs (240 in-lb) and kept on creeping. I got spooked and stopped turning after about 45 degrees of this. All the other bolts would hit 20 ft-lb and would turn just a little but you could feel them firming up. I would take them to 20 and hold them there until they stopped turning.

Here's a couple of things I did that may have been not-so-right:

1. I used a large torque wrench - the only one I have which I used to use for more like 60-80 ft-lb bolts. It has a 150 ft-lb range and 20 ft-lb is low on the scale. The pointer zeros just fine but I fear maybe the calibration is not so good that far down. How much margin do these bolts have?

2. I retorqued the bolts after I had idled the motor for about 5-10 minutes. It was warm (but not hot). All the bolts were slightly loose and turned a little, but less than 20 degrees or so. Except for this one. I have been reading up here and now realize maybe I should stop doing that. When I torqued them cold the first time all was OK.

I would like to think I can just leave it alone. It did come up to 20 and held when cold. If the threads were starting to give I didn't go very far with them. If they are still strong enough to hold up I don't want to screw with them. I did idle it again after this incident, maybe another 10-15 minutes to let it get good and warm and there were no visible issues. I have not had it on the water yet under load.

Thanks for any advice you may have.

Bill

 

[Daviet]

Re: 1966 40hp Johnson - Soft Torque on Head Bolt?

It sounds like you might have some pulled threads in the block. The fix would be to pull the head back off and install a heli-coil in that bolt hole. I have found that a large torque wrench like you used is not very accurate at the low end of the scale, by a cheap beam type torque wrenck if you can't borrow a low reading 3/8 drive torque wrench.
I normally retorque head bolts after I have warmed up the engine and let cool down.
It's pretty much a crap shoot how long before you have problems again. The main thing is if you start getting water in a cylinder and do some damage before you realize it.

 

[yorab]

Re: 1966 40hp Johnson - Soft Torque on Head Bolt?

Agree with Daviet. You should definitely get a fine-scale torque wrench. I learned this the hard way.

I would be prepared to pull the head and install a thread insert as Daviet suggested so that you don't have unseen damage occurring. As a last chance, you could try to torque down that bolt (with the proper torque wrench) one last time before you pull the head. If it torques down, then great, you can leave it alone. If it pulls the threads, then oh well, you were set on pulling the head anyway.

 

[Bay Boater]

Re: 1966 40hp Johnson - Soft Torque on Head Bolt?

I think it's OK.

I crowbarred my wallet open and got the right torque wrench for it. I backed everything off a little in the reverse tightening pattern and removed the suspect bolt. Threads looked clean. Put it back in and retorqued the entire head to the lower end of the book range. Everything clicked right in with no creep. Torqued again at the higher end of the range and they barely moved. So there - let that be a warning to you fellow shadetrees out there. Phew. Knock wood.

 

[boobie]

Re: 1966 40hp Johnson - Soft Torque on Head Bolt?

Always use the proper tools when working on an outboard. Inch pounds are critical.