Installing cylinder studs into triple crankcase

[aebbern]

I am finally getting around to buttoning up my engine after some crank and head work on it by Red.  Quick question for the group - when inserting the studs (long thread end into cranckase) how tight do they need to be?  When I get it finger tight, I still have a thread or two on the stud showing above the crankcase surface... is this correct, or they should they be tightened further?

 

[GregT]

Studs should always bottom out in the hole. Running out of thread on the stud and bottoming on that is a big no-no...

 

[aebbern]

So when they bottom-out in the hole, do I just leave them finger-tight?

 

[breganzane]

Hi Andrew,
I first make sure both stud and hole are clean and free of oil etc, lock two nuts together at the top of the stud (short thread, as you've noted), apply a dab of high strength threadlocker (eg Loctite 262) to the bottom, screw it down by hand, then give it a calibrated twang with a 13mm spanner to snug it down good and proper.  Seems to work fine, studs do not back out when removing cylinder head nuts later.
Cheers
SteveB

 

[Davo]

Is a calibrated thwanger available from Teng Tools?

 

[Davo]

I think Steve means 'skill of the craft' Davo.

Really. I thought he was talking about a real tool 

 

[aebbern]

Thanks Steve - that sounds about right.

I forgot how much "fun" it is getting the pistons back in place... I have come close to giving the whole thing a calibrated kick off my workbench at times

 

[aebbern]

Finally got all 3 pistons & rings in place - took some use of precision kitchen utensils to hold #1 & 3 pistons at just the right height:

 

[CLEMTOG]

The stud heights
measured from the top face of the cylinder block (head joint),
should be,
long 9mmm studs 134mm
short 9mm studs 101mm
7mm near plug studs 89.5mm.

I usually only fit two studs when lowering the cylinder block over the pistons, and you will find it a lot easier to have the cylinder base gasket on the bottom face of the block as you lower it down.

If you have successfully lowerd the block over the piston and have it sat on its gasket nice and snug, the studs should protrude above the top head face (no cam bearings in situ) like this
long 9mm studs 39.5mm
short 9mm studs 12.00 mm
8mm cam bearing studs (into threads in the head) also 39.5mm

The head torqueing sequence is not what you would assume from normal (ie start in the middle and work out)  that does happen but there is some crossing,you need to follow a diagram, which is available elsewhere on the site. Head torque in almost every written manual since 1972 is wrong, so be careful. I know what I do it to, and others disagree so I wont post on that!
CLEM

 

[nick7]

My recollection  is that if the threads have been time carted, the studs do not bottom  out at all? So it is all the more useful to know the correct heights...Clem?

 

[CLEMTOG]

correct Nick
if Timecerts have been fitted then the studs will remain loose when they are at the correct height, that doesn't matter, since when the nut is fitted on top of the head and tightened pressure is put onto both ends of the threaded stud, this might even be better than stock because the threads at both ends are doing the work, with a stud "bottomed" in a crankcase stud the pressure is applied to the wrong side of the thread formations, and of course when it gets tightened the laws of physics determine that the pressure will then transfer to the other side of the thread formation, but did it? has  it? etc etc, much better (well slightly) for it to happen all by itself and the stud stretch along its length, with both stud threads equally sharing the torque.

I now routinely Timecert all 12 crankcase studs whenever I see them, lets face it they have been working as stock for maybe 40+ years, you have to refresh everything from time to time.
CLEM

 

[aebbern]

Clem - thanks for the details on the stud heights - I still haven't buttoned up the head so I'll check them before going any further.

 

[Dellortoman]

correct Nick
with a stud "bottomed" in a crankcase stud the pressure is applied to the wrong side of the thread formations

I disagree Clem. When a stud is tightened against the bottom of the hole, that hole bottom is trying to push the stud out. When a nut is tightened on the other end of the stud, it's trying to pull the stud out of the hole. Both forces are going in the same direction.

 

[CLEMTOG]

you are right (again) Cam, so I bow to your superior technical knowledge, I have thought this for decades and until it was put this way by you, I was blissfully happy with my work, I still am, but in a different light, so I will stick with the tech data that I have amassed over the years and leave the "thinking" part to others.

CLEM

 

[Dellortoman]

Don't beat yourself up Clem. It's only a minor thing and somewhat pedantic of me to point it out. Whether the studs touch the bottom of the hole or not is hardly a matter of huge importance. But I suppose something to avoid would be tightening the stud hard into a blind hole so the thread is well loaded. Then when the nut is tightened at the other end, it'll put more load on the already stressed thread in the crankcase, in which case the thread may fail. Maybe this is the reason studs pull out occasionally. I'd be inclined to put them in with Loctite but not screw them in much more than finger tight.