cylinderhead studs

[dalebrignall]

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 .

[aupickup]

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

[philthehill]

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.

[chickenjohn]

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.

[dalebrignall]

many thanks for the info

[simmitc]

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.

[bmcecosse]

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..