hooken203
Active Member
If you were going to replace the head bolts with studs on a 250 XB. What would you use for a torque spec going back together. Or would you use the 20 ft/lbs plus 90 degrees like the book says?
Head bolts to studs
- Thread starter hooken203
- Start date
ImbadBob
Active Member
Bolts or studs, if its the same thread pitch the clamping force is the same.
I'd contact the stud manufacturer.
I have always been told studs were better. Here is Summits reason why.
http://www.youtube.com/watch?v=Lk7H3TIZSNM
http://www.youtube.com/watch?v=Lk7H3TIZSNM
hooken203
Active Member
This was a question asked in the 3.0 Mercury section on BBC. The torque with the standard bolt is 20 ft/lbs plus 90 degrees. So if the studs are of better quality thread pitch being the same I wondered how did they come to the conclusion that 35 ft/lbs would be where you would put them. Not sure why you would do this unless like stated above you were doing multiple head R&Rs. I just thought that you guys over here may have a lot more experience with this.
SLOmofo
Well-Known Member
I think I'd install Time-serts before using studs. I had studs in one engine, it was always a pain to clean the gasket surface.
hooken203
Active Member
I just wanted to know their method of determining the torque on the the studs. I found out what that is just not sure I agree with it. It was to see what torque it took to turn the bolt 90 degrees past the first torque of 20 ft/lbs and use that number.
SLOmofo
Well-Known Member
I do know that.
What I'd do is look up what was used as the spec before they went to Torque to Yield or Torque Angle method. Make sure the size and pitch is the same. Also if it is lubed and with what. Head of bolt to washer, washer to surface, threads.
A lot of stuff is TTY in the Toyota's I work on, spooky tightening a bolt to the point where it starts to stretch and then some. I don't like the sound, CRACKING as they are tightened or loosened. Also don't like to find a head bolt that spins in it's hole!
What I'd do is look up what was used as the spec before they went to Torque to Yield or Torque Angle method. Make sure the size and pitch is the same. Also if it is lubed and with what. Head of bolt to washer, washer to surface, threads.
A lot of stuff is TTY in the Toyota's I work on, spooky tightening a bolt to the point where it starts to stretch and then some. I don't like the sound, CRACKING as they are tightened or loosened. Also don't like to find a head bolt that spins in it's hole!
hooken203
Active Member
What I find interesting is we used to torque bolts to a given torque of say 75 ft/lbs maybe we did it in two or three steps. Never even thought about replacing all the bolts. Then some engineer decided that was not accurate and the best way was torque to a low number then turn X number of degrees on a second round. To end up very close to the same place. And now we have to replace all the bolts always.
suicidealli
Well-Known Member
I have used both, and prefer studs when being removed often. Most high quality studs are fine thread on the nut end. Also use loctite on the block side. The biggest mistake I have seen is people over torque the stud itself. About 4-6 lbs is max on the block side. On a 2.5 it can tweak the cylinder if over torqued. Per Jim Ruck. Not sure on a 3.0.
Roy
Roy