Quote:
Originally Posted by Pete
Here are few things to think about for head studs.
A thread to be properly used needs to be CLEAN bare metal.
No corrosion, rust or scale. Any of these will corrupt a torque reading.
A thread chaser is essentially an under size tap which will clean out MAJOR rust and corrosion. This device can not produce a correct size CLEAN thread. Like it or not, the laws of physics apply here.
Head stud holes in a block need to be cleaned with a standard tap which will make the thread size as it came from the factory. This operation needs to be done with a fixture that holds the tap in perfect vertical alignment or a machine such as a mill or large drill press.
If the hole does not clean to bare metal then it is too rusted/corroded to hold proper torque and needs to be repaired.
While sometimes not visible, corrosion can account for up to 20% corrupt torque readings before the thread fails.
A sealer such as high temp. RTV can be used on the dead end but a thread lube absolutely must be used on the fine thread end. The sealer should be allowed to dry for at least an hour before assembly.
Head stud holes in a block can be tested before final assembly of the engine with simple home made tools. A 3 inch diameter by 2 inch thick steel slug (BOTH SIDES PARALLEL) with a 1/2 inch hole in the center, a HEAVY HARD steel 7/16 washer, a HARD high nut and a proper length stud. You install the stud through the slug with the lubed nut and washer on top and torque to 80 for a model A or flathead V8. If the thread is good, the torque wrench will have a solid feel. No “floating” or wanting to keep turning.
Good threads will easily go over 100 if you are wondering.
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Just wondering your thoughts on head BOLTS on an 8ba? I always heard never to clean the holes with a tap only to use a cleaner tap. Also per the machinist very experienced with flatheads use number 2 Permatex to seal the threads.