Head re-torque

[Junaid]

Hi guys blew the head gasket, not really sure as to what was the cause

Question is, do I re-torque the head hot or cold

If hot, do I need to do so after the first heat cycle?

If cold, do I re-torque after the first heat up/cool down? or do I need to do 1000 kays again?

[Sean1380]

I always take the car for a drive, come home, let it cool down, then re-torque in the correct sequence.

You have the loosen the nut slightly then torque it back up.

[u09521]

Been there done that
I torqued to spec on cold assembly and started driving around. I kept thinking I have to re-torque but never actually did it, thinking that at the 1000km service I'll do all the bits,  head, rockers, oil etc. etc. So at 950km, coming off the highway at the off ramp, high heat, it blew out between 2 & 3. Lucky for me no water in this area. On replacement of the gasket, now paranoid, I used Spanjaard copper gasket spray, torqued, drove around the block, torqued, drove a little further torqued until there was no more movement in the nuts. The first hot torque was about a quarter turn.
I believe, apart from not re-torqueing early on, that my nuts may have bottomed out on the stud threads originally since the head is not what it was and the studs stick out further than other motors I looked at, so I put an additional hardened HV washer as well. If its a 11 stud head the stud next to the thermostat should also be torqued to half value as there is not much block in that area and there is a danger of breaking out the bottom end of the stud. (that said on the first attempt it was full torque and ok)
So far so good 3900km later, but I'll check them again at the 5000km service next week or so.
Also be aware that stray oil etc. on the threads affects the stud stretch and you may not be developing the clamping force you think, and torque wrenches should be calibrated at least once so you know its working properly. I got mine in about 1980 when I built my first bike engine and was pleasantly surprised to find it still accurate within a couple of percent 30 years later!

[Sean1380]

Oh and ALWAYS loosen off your spring loaded torque wrenches after use !!!!

I didnt, and a head gasket went on the way back from a car show in Dundee once ! thing was showing double what the torque actually was

[yellow1275]

Hi Junaid, mine also blew a few weeks ago. After checking, the centre brass plug had receded slightly, so I had a new one put in. I also went with a copper head gasket, and Spanjaard copper gasket sealer. So far, it is still ok. My engine builder also starts the car, lets it get up tp temp, then lets it cool, down, and then retorques, and as Sean said, loosen and the torque again.

[Sean1380]

Oh and I run a standard Payen BK450 black head gasket on the 1380 !

No sealer needed and it ran like that for over 7 years !

Used another BK450 when i put the new head on last September.

Great gaskets even on block busting 73.5mm bores.

[Boyscout]

Just a note on re-torquing. Be wary of over-torquing. What often happens is that the fire rings on the gasket collapses, especially between the two center cylinders. You don't need massive amounts of clamping force to seal the head. I have torqued the newly resurfaced head to spec and have had absolutely no issues for the past 10000 plus km's. No gasket compounds or sprays were used either.

A friend of mine, who's engine was done by a reputable, well known Mini guru, had the gasket blow between cylinder 2 and 3. On closer inspection the fire rings had been squashed and deformed. This can only be attributed by over torquing.