Securing studs into rebuilt cylinder -advice?

[Tillerman6]

Maybe someone knows this one?  I got the rebuilt cylinder back from Millenium with a chrome bore and new piston,(ended up being a Wiseco piston)  but the 6 studs that hold the head on were not installed.

The threaded holes are in fine condition and very clean, but can someone tell me what sort of chemical(s) should be used to keep the studs from backing off?  I am thinking some sort of Locktite, but I am not sure. Also, the studs have more thread on one end than the other. Which end should go down?.

[feetupfun]

A small amount of thin anti-seize compound on both the thread that goes into the cylinder and the thread that goes through the head. When you tension the head nuts to the correct torque, the force on the threads prevents either of them from undoing.

You should be able to work out which end is which by measuring the lengths of the holes through the head.

Usually the end of a stud that is threaded into aluminium is longer than the end that has a steel nut, because aluminium is softer than steel.

[Tillerman6]

23 hours ago, feetupfun said:

A small amount of thin anti-seize compound on both the thread that goes into the cylinder and the thread that goes through the head. When you tension the head nuts to the correct torque, the force on the threads prevents either of them from undoing.

You should be able to work out which end is which by measuring the lengths of the holes through the head.

Usually the end of a stud that is threaded into aluminium is longer than the end that has a steel nut, because aluminium is softer than steel.

Will do.  And looks like there is a slight difference in the threads on the studs so that the longer end is down in the aluminum.  Thanks for the info!

[section swept]

 

6Don’t overtighten the two stud that are screwed into the top of the cylinder barrel. There is a recommended tightening sequence and the barrel studs are not torqued to the same setting as the through studs. Have a look in the Haynes manual or on line. Basically the cylinder head should be checked for distortion using a straight edge, then it is lightly lapped to the cylinder liner and barrel top using either fine grinding paste or metal polish. Hold the barrel still (second person or lightly clamped in a large vice or similar....lightly where it will do no damage!) ensure there is no old sealant or detritus on the surface areas that seal together, apply the paste, polish and pushing down on the cylinder head using a turning back and forth action lap the two surfaces together. Do this a few times, lift the head off and inspect, you should see a light grey sheen all around both mating surfaces. Repeat if you think it needed. Clean thoroughly by washing off with WD40 or similar or white spirit, dry. Of course if your engine has a head gasket the same applies to the mating surfaces. when you fit the cylinder head tighten the nuts down on clean dry unlubricated threads, if you lube the threads you will not achieve the correct torque value as the lube overcomes friction and allows the stud to be overtensioned. Tighten each nut down with its flat washer in place and free from burrs etc...finger tight. Check this but from memory the four through stud nuts are tightened to 14ftlbs and the inner (barrel stud nuts) are set to 11ftlbs. So after initial finger tightening halve the aforementioned settings so you first torque to 7 ftlbs for the outer four through stud nuts and 5.5 ftlbs for the inner two stud nuts. The sequence is one that spreads the tightening load evenly, looking down on the cylinder head facing forward the head becomes a clock face at 11 o’clock that’s stud one, at 4 o’clock that’s stud two, 1 o’clock stud three, 7 o’clock stud four, at 12 o’clock that’s stud five and 6 o’clock that’s stud six. Basically you tighten as evenly as you can without causing distortion or warping. I hasten to add I’m going from memory so if someone corrects me, fine. Do not be tempted to put anything like sealant or glue or even oil between the surfaces as this will cause a leak, liquids cannot be compressed and as you start and run the engine heat will cause the oil, sealant to expand and be forced out. To prevent corrosion of the exposed threads either smear with high melting point grease or paint. Paint will make removing the nuts a little difficult unless you wire brush the thread first. If you smear the stud threads with copper based product you introduce another metal which could cause electrolytic action, better to use on the threads into the crankcase and barrel a high melting point grease or oil, but only enough to cover using sparingly. It is possible on blind hole to create a hydraulic lock effect which will prevent the stud tightening fully, this hydraulic lock could in some case blow the case. Stud lock (Locktite) will prevent rust but mark removal of the stud difficult, depends how often you want to remove the studs. Coppergrease/paste seems to be many people’s favourite so if you must, you must. I tend to only use that product on disc pad backings and sliders. When you install those studs wind then in with two nuts locked together and just nip them in when home don’t  force them in like their holding the Titanic.

if your engine has a cylinder head copper gasket, the original if in not bad condition could be annealed and potentially reused or kept as a spare.

Edited October 17, 2018 by section swept
Added material

[feetupfun]

13 minutes ago, section swept said:

 

6Don’t overtighten the two stud that are screwed into the top of the cylinder barrel. There is a recommended tightening sequence and the barrel studs are not torqued to the same setting as the through studs. Have a look in the Haynes manual or on line. Basically the cylinder head should be checked for distortion using a straight edge, then it is lightly lapped to the cylinder liner and barrel top using either fine grinding paste or metal polish. Hold the barrel still (second person or lightly clamped in a large vice or similar....lightly where it will do no damage!) ensure there is no old sealant or detritus on the surface areas that seal together, apply the paste, polish and pushing down on the cylinder head using a turning back and forth action lap the two surfaces together. Do this a few times, lift the head off and inspect, you should see a light grey sheen all around both mating surfaces. Repeat if you think it needed. Clean thoroughly by washing off with WD40 or similar or white spirit, dry. Of course if your engine has a head gasket the same applies to the mating surfaces. when you fit the cylinder head tighten the nuts down on clean dry unlubricated threads, if you lube the threads you will not achieve the correct torque value as the lube overcomes friction and allows the stud to be overtensioned. Tighten each nut down with its flat washer in place and free from burrs etc...finger tight. Check this but from memory the four through stud nuts are tightened to 14ftlbs and the inner (barrel stud nuts) are set to 11ftlbs. So after initial finger tightening halve the aforementioned settings so you first torque to 7 ftlbs for the outer four through stud nuts and 5.5 ftlbs for the inner two stud nuts. The sequence is one that spreads the tightening load evenly, looking down on the cylinder head facing forward the head becomes a clock face at 11 o’clock that’s stud one, at 4 o’clock that’s stud two, 1 o’clock stud three, 7 o’clock stud four, at 12 o’clock that’s stud five and 6 o’clock that’s stud six. Basically you tighten as evenly as you can without causing distortion or warping. I hasten to add I’m going from memory so if someone corrects me, fine. Do not be tempted to put anything like sealant or glue or even oil between the surfaces as this will cause a leak, liquids cannot be compressed and as you start and run the engine heat will cause the oil, sealant to expand and be forced out. To prevent corrosion of the exposed threads either smear with high melting point grease or paint. Paint will make removing the nuts a little difficult unless you wire brush the thread first. If you smear the stud threads with copper based product you introduce another metal which could cause electrolytic action, better to use on the threads into the crankcase and barrel a high melting point grease or oil, but only enough to cover using sparingly. It is possible on blind hole to create a hydraulic lock effect which will prevent the stud tightening fully, this hydraulic lock could in some case blow the case. Stud lock (Locktite) will prevent rust but mark removal of the stud difficult, depends how often you want to remove the studs. Coppergrease/paste seems to be many people’s favourite so if you must, you must. I tend to only use that product on disc pad backings and sliders. When you install those studs wind then in with two nuts locked together and just nip them in when home don’t  force them in like their holding the Titanic.

if your engine has a cylinder head copper gasket, the original if in not bad condition could be annealed and potentially reused or kept as a spare.

Sounds like you are thinking of a 5 speed Bultaco engine rather than the Yamaha TY250 motor he is working on.

[section swept]

Blow me down, you should be a detective...what was I thinking of. Still at least you took the time to read my piece??Thanks.

[tony27]

Seem to remember the studs have flat ends on the longer thread which are the ends that go into the barrel, the shorter end is slightly domed

[scifi]

If your studs have a coarse and fine pitch, the fine pitch nut end should undo before the coarse pitch.   On old British engine studs, the coarse pitch was BSW and the fine was BSF, mostly used in cast iron parts without lubrication or Loc-tite.

.