Head stud

[mikeday]

Opened the bonnet of the TR4A today to find one the head studs sticking up from the head. The stud was lose and I pulled it out of the head to find that it must have sheared off as there was no thread on the base. I have not driven the car for a couple of months, was fine than,  and it has been undercover in my car port. I checked the water level to find that it was well down but not empty. There was no water in the sump. Any ideas how this stud could have cracked - there was oil in the stud seat? I fear this could be expensive!   

[RogerH]

Hi Mike,

 the studs are fitted with a very high torque. If the stud becomes corroded and has enough thinning it could easily shear and when it lets go it will try to fly off.

The tight hole it is in will restrict its flight.

Which position does the stud come from  - is it a long one   or a shorter one

Roger

[Motorsport Mickey]

A slight amendment to what Roger says, the studs are fitted...with no torque, screwed in by hand until the thread abuts the thread in the block, then you stop turning. The 105 lb ft applied to the cylinder head nuts of course transmits down through the stud and into the bottom coarse thread and into the threads of the block.

A little more information will help, which stud is it, describe it as passenger side or drivers side and count the studs back from the front. You say the stud has sheared, has the stud sheared across the stud (uneven break exposed) or has the bottom thread on the stud stripped off ? It may be the block has been misused by a previous owner causing stud damage on the bottom thread, it is possible to rethread the cylinder block holes...even the longer studs (have the tap welded onto a steel rod and file a square drive onto it's upper end). With any luck the studs thread remains are still intermingled in the thread form and application of the tap gently by hand can often pick up the thread lead in (turn the tap backwards until you hopefully feel the tap "nudge" as it drops off the second thread and into the first thread groove, then turn gently forwards) and with plenty of cutting oil (sounds like you have some there anyway) you can eject the stripped thread without damaging the block thread. In the event the block thread is stripped or damaged, helicoil the block thread and away you go, there is sufficient block material to take the helicoil larger thread (I've retapped a stripped block on a deep hole up to 16mm when a swift repair was needed).

Mick Richards  

Edited April 14, 2022 by Motorsport Mickey

[mikeday]

The stud is on the drivers side, on the side of the block, four back from the front. It has sheared off with none of the thread on the base of the stud. Hope this helps.

[RogerH]

So, item #14 Here - it is a long one.

You will need to remove the piston & liner in order to get sight of the stud end & hole.

Although there was enough force to pop the stud the remnants may not be too tight in the hole.

If you can get a Left Hand long series drill bit - 1/4" diameter or so it may actually unscrew itself when drilling (if you are lucky).

However you may well have to open the remnants up so as to get an extractor in place.

If the engine hasn't been out for a while it may be worth removing and giving it some TLC etc

Roger

[Lebro]

Depends where it has sheared off, he may be lucky & with the head off there may be some of it still above the block surface, or at least level with or slightly below the block surface.

Bob

[Charlie D]

Measure the exact length of the part that has come out, and then you should be able to work out how far into the block the breakage occurred.

You are going to need to remove the head, whatever you find though.

Charlie.