Topic: retorqueing cb750 head

[junior]

After some disassembly and removing the head to trace a leak it has dawned on me that retorqueing the head would be quite involved. Other brands I have rebuilt varied as to needing retorqued. This being my first Honda, to do this, after a couple warm-ups, as you know, would require removing the engine and the camshaft. How do the experienced get around this? Is there a preferred head gasket? Or is it not necessary on cb750's Thanks, Jr.

[scottly]

I have never found it necessary to re-torque a head gasket after running an engine. They certainly didn't do it at the factory when the engines were first assembled.  

[jaytee-nz]

Yes, what Scottly said.
In terms of a preferred head gasket, definitely use a genuine Honda one if you can find it.

[calj737]

If you aren’t changing the head studs, then a re- torque is not really necessary. Yes, the gasket does compress and the head nuts might lose a bit of torque, but heat cycles aren’t truly needed to generate a re-torque. If you want, you can torque the head, wait 24 hours, release the nuts (use the reverse sequence) then torque back.

It’s a small insurance policy but it’s a heavily debated topic of need versus best practice.

No manufacturer torques heads after assembly, that’s true. But there are plenty of high end engine builders that do. Who’s to say which is right?

[Tracksnblades1]

If you have a stand or old engine frame cradle you could test run it through a few full heat cycles.
That said, I’ve never experienced a head gasket that you couldn’t get the head bolts or stud nuts to turn some after a full temp heat cycle. Regardless of what head gasket types. I know your pain here better now than have to later..

Some of the modern commercial engines head torquing regiments can wear an older guy out.
3-4 incremental torques, back them clear off, 3-4 incremental torques again, wait required set time, 1st degree turn,
Wait required set time, 2nd degree turn…..😣 …what the factory will do to offset the cost of a retorquing…😓

P.S.      PEWE has posted just leaving the 750 engine overnight and then retorquing the nuts the nest day will yield some additional turn. But, I’m not remembering whether its an < or > a 45* additional turn..🤔

[pjlogue]

If you aren’t changing the head studs, then a re- torque is not really necessary. Yes, the gasket does compress and the head nuts might lose a bit of torque, but heat cycles aren’t truly needed to generate a re-torque. If you want, you can torque the head, wait 24 hours, release the nuts (use the reverse sequence) then torque back.

It’s a small insurance policy but it’s a heavily debated topic of need versus best practice.

No manufacturer torques heads after assembly, that’s true. But there are plenty of high end engine builders that do. Who’s to say which is right?

I  agree with what Calj737 said.  If your head and jugs are flat and you have a good quality gasket, it should be fine.  I do retorque a head after 24 hrs of initial torque upon assembly, before engine installation just to be sure.  The easiest thing I have found is to carefully clean the head/jug mating surface and then use a machinist dye to coat the mating surfaces of both head and jugs.  Then get a known flat surface (machinist granite block) and use 1000 grit wet/dry sandpaper, wet it and run the part face over it. All it takes is a few strokes to tell if a head or jug is not straight.  This also picks up slight blemishes in the surface (perhaps from a rough treatment from gasket removal.)   I think mill decking a head/jugs is way overkill.  To much material removal for a normal rebuild and can lead to valve interference with the piston.

-P.

[BenelliSEI]

+1 to above. When I did my last top end I pulled the head down just before we went on a month long vacation. On the second pull (stock hardware and studs on a ‘69 cb750) I was surprised how much more I got……

[willbird]

+1 to above. When I did my last top end I pulled the head down just before we went on a month long vacation. On the second pull (stock hardware and studs on a ‘69 cb750) I was surprised how much more I got……

That is pretty crazy really considering this is what Honda used for head studs