snapped head bolt size?

[wickermonkey]

Well spotted indeed, looks like thats had some abuse

[wickermonkey]

feck feck feck. Bloody bolt, well as you can tell it hasn't gone well ive got all of the old studs out, one was exceptionally tight, and then to the broken stud i took. thankfully it drilled well, soaked it in penetrant for a while, warmed it up a bit and tried the easy out. after breaking the tap wrench in half and nearly taking nost of the skin of the inside of my arm ive ended up drilling out the hole as large as i can so that i can tap out the hole, if that doesnt look like its going well i should be able to borrow the mag drill from work and helicoil the damn thing. Welcome to the world of classic car ownership

[bmcecosse]

I thought it was broken at the top??

[MarkyB]

Easy outs are the spawn of the devil!
You have a bad problem, they tend to make it much worse.

[les]

I must say i've not found this the easiest of posts to follow! Don't drill the hole too big, keep it undersize and see if you can pick the remaining metal from the threads. The thread needs to be good for when you torque up the head. If any doubt use the helicoil you mentioned.

[bmcecosse]

I'm not 'getting it' either.... Has the head been removed and all the studs pulled - so you were left with the one broken stud - and it won't come out?? Bang it with a hammer - heat it with a blow lamp - use stillsons on it (it's scrap anyway) - but DO NOT ever use 'easy out' (a misnomer if ever there was one. What have you drilled????

[les]

I stand to be corrected but I would say he has now removed all the studs and is left with the broken one (broken 1 thread below the block face) which has been drilled out as much as possible. My last thread relates to this being the case.

[wickermonkey]

Les has got my drift. I know easy out are the devils spawn, broken many off at work, but because the other studs were quite easy to screw out I was hoping the broken one, below the block, was going to be as well. With a small hole plus easy out would not have swollen the thread if it came out easy but it never (soaked in everything n anything I could find plus a bit of heat). The drill was on center so I've drilled out as much as I dare, can't see thread yet but it's not far off, and I'm going to try tapping the hole. They have got some nice sharp expensive taps at work. Fingers crossed

[bmcecosse]

Ahh right -it's confusing because before you indicated it had snapped at the nut... I would continue to shell it out. The drill size for that thread is 5/16". At that point you should be able to pick away the remains of the old stud using a sharp pick probe. If you go any larger than 5/16 the thread will be weak.

[les]

Yes that would be best. Retaping with metal still in the threads might stop you following the original thread. Good luck with it.

[wickermonkey]

I've got it out to 7.5mm at the moment (5/16 is about 7.9mm) gonna have a rumidge about at work for the right size drill and ive got one of our machining contractors dropping off the taps today, so hopefully but the end of the night i should have it all back together.

Sorry for some of the confusion in earlier posts, i read back through and nothiced that i had put it was broken in the head and should have put block

Anyway fingers crossed for a quiet day at work so that i might have enough enthusiasm after 12 hours to get my head under the bonnet for a couple more

[IslipMinor]

5/16" = 8mm, within a couple of thou!! Makes finding a drill easier probably?

[bmcecosse]

Not in my garage it wouldn't! No nasty metrics for me...........

[wickermonkey]

Well everything is back together and working. Not to bad seeing as though ive never taken an engine apart. drove it to work this morning and all seemed fine, bit flat in 4th but might just need a bit of tuning

[bmcecosse]

Be sure to retorque the head (44 ft lbf) after the first heat cycle - and reset the valve gaps. 12 thou inlet 15 thou exhaust