Head bolts question + followup

[Pentax645]

Most interesting data on clamping force. Wow.

[Dan Timberlake]

1000 lbs of engine etc suspended by 2 bolts is about 500 lbs per bolt and at most 1000 lbs.

Tightening a 7/16" head bolt to just 45 ft-lbs exerts almost 7000 lbs of clamping force.
http://www.repairengineering.com/bolt-torque-chart.html

[showbizkid]

Threads merged to keep the discussion together.

[rkapteyn]

Check the length of the bolts.
The Champion engine had two bolts that were longer to bolt on the ignition wire bracket.
If you did not pay attention and replaced the shorter bolts with the longer ones ,the long ones will bottom out and not tighten.
Robert Kapteyn

[jackb]

....I'm in the company of you might need to replace the head bolts. Lifting angularly and sharing that weight with at least another screw or 3 isn't anything like compressing the head and block together to sandwich a gasket under constant, repetitive pressures.....not to mention you're continuing to do damage to the screws and the deck......GL

[Pentax645]

The threads in the block are still sufficient to allow me to lift the motor, trans and overdrive by lifting from two head bolts. With that, they are more than adequate to hold the head down. Of course, I'll keep a proper antifreeze solution in the motor.

[GinettaG12P]

It sounds like there is a greater chance of stripping the threads in the block than breaking the bolt.

[RadioRoy]

It might be time for a few new head bolts. You would not one to break off in the block.

[Pentax645]

Follow up on Head Bolts

In an earlier post I wrote that antifreeze was seeping up from underneath the center head bolt on my 170 ci Champion motor. The advice I received was to apply pipe dope or aviation gasket material. That was good advice. After draining the antifreeze I loosened the bolt a turn and found that it wobbled quite a bit while still screwed into the block. Apparently corrosion takes its toll on the threads and the clearance loosens up. Although it was proper to simply apply light oil to the head bolt before installing it in a newer motor, it is now necessary to apply a sealer to prevent the antifreeze from working up through the threads.
Thanks to all who responded to my inquiry.

[52-fan]

I don't remember putting anything on the bolts in my Champion engine and it was fine. To be safe, check the shop manual and do what it says.

[DieselJim]

I'm not sure I know what pipe dope is. Surely you don't mean the product that plumbers use on water pipes, do you?

Yes. Coat the threads. Use non harding.

[sweetolbob]

I hope I didn't come across negative in my response. It was not my intention.

No reason to suspect you were negative in your response. I used Permatex #2 but they as well as others make specific thread sealers. You'll get other suggestions for the forum, certainly by folks that know more than I do but you could just go to your local auto store that does rebuilds and buy what they like.

It's prudent to check all the other variables suggested but I was just trying give you a quick idea of a possible solution that would not require disassembly. In any case, head bolts should be cleaned and lubed to give good torque values.

Best, Bob

[Pentax645]

I'm not sure I know what pipe dope is. Surely you don't mean the product that plumbers use on water pipes, do you?

[jackb]

....ah....don't go so far so fast.... A few things come to mind: out of surface head and /or engine deck(block). If both were not examined for warpage or heat distortion, you might have mis-mated surfaces. How about the head gasket ? Did you use any sealant ? Varying opinions from many. Did you tap all the head bolt holes and true the bolts and dip slightly in oil or a film of sealant ? And finally, did you re-torque the heads once they warmed up to temp and then 500 or so miles later ? Any of the above can be your problem(s). Start with the easiest 1st.

[Pentax645]

I hope I didn't come across negative in my response. It was not my intention.