Morris Minor Owners Club

i am going to change a cylinderhead ive left the nuts on the head soaking in plus gas for over a week wirebrushed the nuts and the bit of stud that pertrudes,re soaked in plus gas had a quick go at trying to undo but to no evail .going to try and do the job on sunday will apply heat to the nuts but i am not hopeful .last thing i want to do is break a stud .the only other thing is split the nuts , if i do this could you tell me the thread size of the cylinderhead studs so i can run a die down them to clean up the threads many thanks .will need to buy a tap and die set , never mind .

can you try tightening a tad to release the rust sometimes it works, but again be careful

The stud thread at the top is 3/8" x 24TPI UNF and the bottom is 3/8" x 16TPI UNC.
this is a link to a company where I get all my taps and dies from:-
http://www.engineering-supplies.com/pro ... -die-nut-/
You can get the UNC die nut from them also.
Having removed the cylinder head stud nuts soak the stem of the stud with release/penetrating oil. The sides of the stud usually get cloaked in carbon and crud and which results in difficulty in lifting the head.

aupickup wrote:can you try tightening a tad to release the rust sometimes it works, but again be careful

Yes, this can work, also as mentioned, heat. Even a blow torch can help release rusted nuts although oxyacetylene is much quicker. Also give them a tap from above with a hammer (gentle tap), the shock will often release the rust bond.

many thanks for the info

When you come to lift the head, leave the plugs in and turn the engine briefly on the starter - this will normally lift the head enough under compression to break any seal and get it moving, after which you can just lift it clear.

I've never heard of head nuts not releasing - at least - not on a running engine ! How hard are you trying? You NEED to use a 9/16 ring key - or a socket and ratchet/T bar. NOT an open end spanner. They WILL release! DO NOT attempt to split the nuts... Always possible the complete stud may unscrew from the block - if it does - don't panic... You can get the nut off and then refit the stud. I wouldn't apply heat except as a very last resort..the suggestion to tighten slightly is good - and of course - MORE release oil - although these studs/nuts are usually oily enough to not give any problem. The 4 smaller 1/2" nuts holding the rocker pillars should always be loosened BEFORE the head nuts - and finally tightened when fitting the head AFTER the head nuts have been torqued down..