What is the stock size of exhaust manifold studs... 1.25mm? How long at they? Is the size the same both in the head and the nut that threads on, or are they different. Thanks for any info.
exhaust manifold stud questions.
- Thread starter Suprapowaz!(2)
- Start date
M10x1.25, 52mm long. Threads are the same on both sides. Short (head) threaded side is 14mm long...Long (manifold) threaded side is 33mm long.
First of all 1.25 is not a bolt size, its a thread pitch. Second of all if your looking for exhaust studs than chances are the threads in the head are junk. This is a common problem with the 7m motors. Driftmotion offers a relatively simple solution. check it out. http://store.driftmotion.com/static/i-716exhauststudkit.php If you do this be sure to plug the exhaust holes with a rag or something to make sure no metal shavings get into the engine.
Correct me if I'm wrong jdub but its the recurrence of annealing that causes grain growth, which weakens the metals mechanical properties. that combined with the force applied on the threads from the torqued studs destroys them.
questions for jdub or anyone else that can answer them
1 why does the head reach temperatures that allow annealing to occur is it insufficient cooling or something else.
2 why does this render the entire head junk, is it related to head warpage or something else?
questions for jdub or anyone else that can answer them
1 why does the head reach temperatures that allow annealing to occur is it insufficient cooling or something else.
2 why does this render the entire head junk, is it related to head warpage or something else?
Short answer: Annealing makes the head soft.
1) Most of the time it's when the motor overheats due to the various reasons that are common on a 7M. Compounded by the owners insistance on driving it.
2) A soft head will deform...warpage is one way of looking at it.
1) Most of the time it's when the motor overheats due to the various reasons that are common on a 7M. Compounded by the owners insistance on driving it.
2) A soft head will deform...warpage is one way of looking at it.
Ok, this is what happened. I yanked my engine to send off to get rebuilt. While I had it on the engine stand I disassembled it. While taking off my exhaust manifold the nut was very hard to break loose, so I took an impact gun to it. Thinking that it wouldn't do any damage loosening a nut I took the first one off. The power of the gun immediately remove the nut along with the stud and some aluminum shavings. So I ruined the fist one. The rest of the nuts I decided to use PB blaster, and removed them by hand. The rest of them came out with ease.
I took my head to the machine shop just to check for straightness, make sure the valves where seating correctly, have new valve stem seals installed, mill it straight to accept a MHG, and to get that one stud hole I stripped repaired. Turns out they retapped and heli coiled all of my exhaust stud holes by accident. They thought I asked for all of them to be retapped. Why the hell them would remove all of the studs and retap them is beyond me. That just didn't make sense. Being that there are 7 @ $12.50 each I didn't want to pay an extra $75 for something I didn't ask for, so they took that price off. I asked for my studs back, and they just told me I could pick them up somewhere cheap. I didn't argue, I just took my head and left.
So I'm thinking that it was the power of the impact that ripped it out, and hopefully not a softened head. And I do know that 1.25 is the thread pitch of a stud. I didn't know the nut size, or the length of one. I do vaugely recall that the stud had a space in between the threads that the manifold sat on. Would it be bad if I bought studs that didn't have that space? You know, studs that had threads throught the entire length of it?
I took my head to the machine shop just to check for straightness, make sure the valves where seating correctly, have new valve stem seals installed, mill it straight to accept a MHG, and to get that one stud hole I stripped repaired. Turns out they retapped and heli coiled all of my exhaust stud holes by accident. They thought I asked for all of them to be retapped. Why the hell them would remove all of the studs and retap them is beyond me. That just didn't make sense. Being that there are 7 @ $12.50 each I didn't want to pay an extra $75 for something I didn't ask for, so they took that price off. I asked for my studs back, and they just told me I could pick them up somewhere cheap. I didn't argue, I just took my head and left.
So I'm thinking that it was the power of the impact that ripped it out, and hopefully not a softened head. And I do know that 1.25 is the thread pitch of a stud. I didn't know the nut size, or the length of one. I do vaugely recall that the stud had a space in between the threads that the manifold sat on. Would it be bad if I bought studs that didn't have that space? You know, studs that had threads throught the entire length of it?
Use either Toyota OEM (new) or ARP with 12pt nuts & washers (hold on to your wallet). The stop on the studs is there for a reason.
Your impact could have easily been the cause...galvanic corrosion between the steel stud and aluminum.
The shop helicoiling all of the stud holes did you a favor...I do this as part of a head re-build. BTW - $75 was cheap for doing that job. Helicoils in aluminum mating to steel studs is much stronger...this is very common practice on aircraft. Makes excellent sense to me
Your impact could have easily been the cause...galvanic corrosion between the steel stud and aluminum.
The shop helicoiling all of the stud holes did you a favor...I do this as part of a head re-build. BTW - $75 was cheap for doing that job. Helicoils in aluminum mating to steel studs is much stronger...this is very common practice on aircraft. Makes excellent sense to me
400c on the exhaust side isn't all that hard to get to... :nono:
A qt low in coolant and you have a nice little steam generator at the top of the engine and very little cooling and an annealed head in no time at all.
We get that you understand the engineering/physics behind it Lewis no need to be a smartass about it.
A qt low in coolant and you have a nice little steam generator at the top of the engine and very little cooling and an annealed head in no time at all.
We get that you understand the engineering/physics behind it Lewis no need to be a smartass about it.
^ Indeed. I was just going to point that out. I'm unaware what the head is made from but it has to be one of the heat treatable alloys. The temperature required to anneal any of them (appx 800 F) is easily achieved on the exhaust side. The cooling rate has to be fairly slow and relatively constant but the chances of that occurring are far from impossible given the application.
Thanks guys. I don't think my wallet can handle anything exotic right now. Although I did just recieve a check back from BofA due to an overage on my escrow.
Just buy the Toyota studs then...the $1.50 each is well worth it
You really do not want to go the hardware store route on these.
You really do not want to go the hardware store route on these.
IJ.;1313242 said:
This was the answer is was looking for, i wasnt sure what caused it. also, wasnt trying to be a smartass, sorry if i came off that way.