head bolt tension

[NJona86FJ]

Gday fellas. My head is weeping oil rh side put spanner on nut, bit loose. Need to know tension for head bolts in foot/pounds. Thank You! Most urgent
Cheers Neil.

[The General]

Gday fellas. My head is weeping oil rh side put spanner on nut, bit loose. Need to know tension for head bolts in foot/pounds. Thank You! Most urgent
Cheers Neil.

You`re definitely talking head bolts ay mate - not valve cover bolts?

[NJona86FJ]

.Uyup.the bolts holding the head down to the cyliner bloc.typing on ph. Weeping from gasket on from front rh side of the gasket. Definatly head bolts just need tension as one bolt was loose want to check them all. Have tension erench b. Vheers neil

[The General]

.Uyup.the bolts holding the head down to the cyliner bloc.typing on ph. Weeping from gasket on from front rh side of the gasket. Definatly head bolts just need tension as one bolt was loose want to check them all. Have tension erench b. Vheers neil

page 160 table2 of clymers says, cylinder head nuts 6mm are 7.2 ft-lbs, 8mm nuts are 14 ft-lbs. interestingly cylinder head cover bolts are 7.2 ft-lbs.

[NJona86FJ]

Cheers. Didnt think they were a lot forgot manual best to be safe thanks again would post pic but pmn ph

[racerrad8]

If you are talking about the cylinder head studs, which are a 10mm stud with a 14mm nut, the correct proper torque is 25 ft lb.

Randy - RPM

[yamaha fj rider]

If you are talking about the cylinder head studs, which are a 10mm stud with a 14mm nut, the correct proper torque is 25 ft lb.

Randy - RPM

This is what my Yamaha service manual says also.

Kurt

[NJona86FJ]

Pics in my gallery yes they are head nuts and the one above the leak was loose did comparison check on other nuts just dont want to over or undertension. Is the side of engine that bird hit at 150 odd that only onne nut loose. Will go eith yammy specs dont trust clymer manual bhad issues before. Thanks agaain still out in boonirs lolon ph internet small screen and fat fingers lol.
Cheers neil

[FJ1200W]

If you are talking about the cylinder head studs, which are a 10mm stud with a 14mm nut, the correct proper torque is 25 ft lb.

Randy - RPM

A blast from the past - I'm still leaning towards keeping my APE studs mainly because of cost.

APE recommends to torque nuts to 36-42 ft. lbs on their studs - could that be a contributing factor to the issues with these studs?

What if - what if they're torqued to stock spec? Probably blow the head gasket?

Fun fun fun

[CutterBill]

...APE recommends to torque nuts to 36-42 ft. lbs on their studs - could that be a contributing factor to the issues with these studs?

What if - what if they're torqued to stock spec? Probably blow the head gasket?

Good morning, all. Just for the sake of discussion around the digital campfire... APE says 36-42? Wow, that is a big jump from 25 ft/lbs. That could easily cause stud pull-out. Just because a stronger-than-stock stud is screwed into the case, doesn't mean that the threads in the case are now magically stronger. We all know what happens when you over-torque a fastener.  

Interesting engineering trivia: You can't use just any aluminum alloy for casting. Cast aluminum parts are usually made from 356, or sometimes A356, which has a yield strength of about 18,000 psi. Everyone's favorite 6061-T6 has a yield strength of about 36,000 psi, or roughly twice as strong as A356. So over-torqued threads in a block of 6061-T6 might hold, where the same threads in A356 would pull right out. So why not use 6061 for casting? Because... I don't know. I've asked around and apparently, 6061 just won't flow like the casting alloys. Or it develops porosity. Or... any number of bad things. I'm not really sure but the foundry guys tell me that it just doesn't work. And I have to believe them. So when you see somebody replacing a cast aluminum part with a machined-from-solid part, that's why they are doing it. It's stronger. Ok, back to the studs...

Torquing the APE studs to the stock 25 ft/lbs by itself won't cause the head gasket to blow. After all, torque is torque.  25 ft/lbs on a fat (APE) stud will create the same clamping force as the same torque on a skinny (stock) stud.  BUT... that 25 ft/lbs will not allow the fat stud to stretch as much as the skinny stud. Without the proper amount of stretch, the head nuts may not stay torqued. So the head nuts loosen, the clamping force on the head gasket is reduced, and the gasket blows.

Now, I actually have a set of those APE studs, purchased long ago before I heard of the stripped case problem (Anybody want to buy them?   )  And I've wondered if I could turn/grind down the shanks of those studs to match the shape and contour of the stock studs. Would that work? I dunno. Anybody volunteer to try them? But what if the APE studs are made of a stronger material than the stock studs? If we machined the APE studs to stock dimensions, they would still be stronger than stock, and might lead to the case stripping. Sure we could do a hardness test, then figure out the percentage increase in strength, divide by pi... It just isn't worth the effort. Think I'll just make them into wind chimes or something equally useful.

Time for more coffee....
Bill