15 replies to this topic

[racingbob]

oh dear your going to laugh at this one

I recently rebuilt my mg metro engine torqued the head down fine about 45 lb

when came to tighten down 200 miles later used a different new torque wrench

and the head went down a fair bit alas ( thinking what the hells going on here ) now i know i was reading this new torque wrench WRONG
had a stupid step up showing setting on the wrench

old one showed level across for corrcet poundage which wasnt mine and the one i used to use years ago
was straight across, been out of minis for many many years
so it must be at least 65 its been over 1000 miles now and all is fine
AT THE MOMENT

should i back off a bit and re tighten or just leave
i personally think i should just leave i think messing with it will definitly cause a problem

just rechecked the tappets again this afternoon there fine, however when overtightend the head 1000 miles
ago had to re adjust

god im and idiot for not reading it right, how i found out was the other day thought i would
torque wheel nuts and thinking this more than 45lb as so used to doing wheel nuts when i raced

[charliedurrant]

Bob,

These things happen, I read the wrong line in the Haynes manual and overtightened my ball joint retaining nut and blew the spit washer apart. It's easy to make mistakes.

Personally I would, and I stress I haven't ever over torqued the cylinder head by >50%, remove the head, check for any cracks, use a straight edge to check for warping, replace the gasket and go from there. Atleast the cylinder head is not aluminum.

Charlie

[racingbob]

Bob,

These things happen, I read the wrong line in the Haynes manual and overtightened my ball joint retaining nut and blew the spit washer apart. It's easy to make mistakes.

Personally I would, and I stress I haven't ever over torqued the cylinder head by >50%, remove the head, check for any cracks, use a straight edge to check for warping, replace the gasket and go from there. Atleast the cylinder head is not aluminum.

Charlie

Hi Charlie,

you got me thinking on that one cracking the head

maybe i could just back off nuts a touch a bit evenly at a time and then go forward say
to 55 lb

its not taking off the head im worried about its the exhaust manifold
its getting the head past the studs, unles just undoing the clamp to the gearbox
will be enough to pull the exhaust back from the studs. last time i messed with the exhaust lcb it was awful
you need a proper ramp

only good thing about taking off the head gives me a chance take it up to brian slark for some improvement

[Sam Walters]

I wouldn't worry about it. If it seals alright this time. Don't bother doing anything.

In the future i would get a new set of studs and nuts mind. If the head gasket does go its no worry to change them then.

[charliedurrant]

I wouldn't worry about it. If it seals alright this time. Don't bother doing anything.

In the future i would get a new set of studs and nuts mind. If the head gasket does go its no worry to change them then.

I guess Bob you have two choices, leave or muck about. Sam is correct to renew the studs as they may have stretched.

I've not had a problem with the LCB when up on axel stands, just drop the exhaust and pull it about to disconnect the 'Y' piece. I does all add to the bother.

On reflection, if the head is gone, it's gone so maybe Sam is right to just leave it. Hopefully someone else who has acutally done it can comment.

[matty...]

I wouldn't worry about it. I found out that my old torque wrench had gone out of calibration.

When I compared it to a new one, it was reading 30% lower than the new one. So my head bolts were 65/70 lbs!

I would leave it. But make sure next time you do the head gasket replace all of the head studs.

[racingbob]

I wouldn't worry about it. If it seals alright this time. Don't bother doing anything.

In the future i would get a new set of studs and nuts mind. If the head gasket does go its no worry to change them then.

I guess Bob you have two choices, leave or muck about. Sam is correct to renew the studs as they may have stretched.

I've not had a problem with the LCB when up on axel stands, just drop the exhaust and pull it about to disconnect the 'Y' piece. I does all add to the bother.

On reflection, if the head is gone, it's gone so maybe Sam is right to just leave it. Hopefully someone else who has acutally done it can comment.

maniflow put all this sealant on when recently doing it only just 500 miles ago
i know last time tried taking off under the car was unbelievingly difficult when using sealant

im panicking now going to crack the head thats why said maybe back off a bit and redo up
so not QUITE so much its done up 20lb more than should be, but cars going GREAT

[matty...]

If you back it off then retighten it to a lesser torque, you are not going to compress the head gasket as much as it was, so you will likely have to replace the gasket, as it will more than likely fail soon after.

Ive been there got the T shirt, and when I had to replace the gasket, I snapped the head stud the next time I retorqued it to the correct torque.

My advise, leave it, or replace the head gasket with a new one and replace the head studs while you're at it.

Edited by matty..., 07 January 2012 - 06:30 PM.

[racingbob]

thanks guys,

its my second fun car so dont use all the time, maybe will keep close eye on it

[tiger99]

Don't worry about the gasket, or the expensive bit, the head. The real problem is with the head studs, which have now been stressed beyond their design limit. It is not unlikely that if you back them off, and retorque to a lower torque, they will actually snap. You can take them up to the design torque many times, but if you go well above that you are in the fatigue range and the number of load cycles before failure may be very small, like maybe one, which you have used.

I would be inclined to leave well alone for now, but within maybe 5000 miles think about a new set of studs, and of course a new gasket. The head will be ok. It is cast iron, and A series heads are robust.

[Shifty]

Yeah, I wouldn't be hugely concerned, the head studs would snap before any real damage has been done.

I don't think you'll have a problem.

[bmcecosse]

Leave well alone - but you were lucky to not strip or snap a stud/nut. And yes - I wouldn't use them again.......

[Frisco]

Id be more worried about pulling the thread out of the block than anything on the studs

[racingbob]

got up early thismorning thought i would get the torque wrench out
and gradually go up the torque on one of the head nuts, started off of
on a CORRECT 40lb setting on the wrench and gradually turned bit by bit
40, 42 44 looks like they are about 58. so not as bad as i thought
i know i used to do my race mini years ago to 50 and was fine
so going to leave well alone, unless i have reason to take off

thanks for the replys

[Wil_h]

I can see no way that the head could be damaged, the studs would strip before the head got damaged. Again, if the studs are not failed then they should be ok.

The biggest problem is possible damage to the fire rings. I was using a head gasket that was specified at a much lower torque than the Haynes suggests. I ignored this and torqued to standard, the fire rings cracked and the gasket failed after a few thousand miles. I then used the correct torque on the next gasket. This failed in a classic under-torqued manner, i.e. blow by the fire rings pressurising the water.

So that new amazing head gasket type has never been used again.