possible solution to constantly retourqing head bolts

When I was running a stock cylinder head, I was having all kinds of trouble. This problem with the nuts coming loose, and many other running problems come from the engine and cylinder head getting too hot. And it's not just because there isn't enough cooling fins to adequately cool the head, but the stock combustion chamber shape is inferior and can allow detonation to occur. When this happens, the engine temperature will get very high. Aluminum has a high expansion rate, much higher than that of the steel studs. This is why your engines are having problems. It is not the fasteners fault. Get a properly designed cylinder head and your problems will go away.
-Fred
 
I run a Puch head, 8mm grade 12.8 metric studs with helicoils in the cases, hardened washers as well as hardened nuts and custom copper head gasket that I build myself. It takes 3 heat cycles/retorques then their tight. My head runs cool.
I also used to run nitrous injected dragbikes with springsteel steel headgaskets and they all required head retorques so I question the fact that it is a "properly designed cylinder head". That engine in my motorcycle was top notch and worth a fortune in in top shelf components. Heat cycling and head retorques are part of the norm.
I also work as a machinist doing prototypes and work with engineering team and have queried them on this matter, heat cycling is a fact of life in their opinion, take it for what it is IMHO.
 
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Right.
I understand what you are saying. After things warm up and cool, things will settle, so re-torquing is necessary. That makes sense, and I trust your experience to be right on the money, for sure. However, a lot of the problems people, including myself have experienced don't fall into that category. The puch head that you run has much better cooling than the stock heads. And although the combustion chamber dimensions are not ideal for these motors, that head offers a significant improvement over the stock head. The stock heads not only have no squish band, but they have limited cooling. The combination of those two factors make the stock engine susceptible to detonation (especially the PK-80), which then, as you probably know will cause a severe increase in engine temperature. Since aluminum has a significantly higher coefficient of expansion in comparison to the steel studs, the the top and bottom gaskets will get squashed in these conditions. This is why some people have this never ending problem with studs and nuts, not to mention the serious engine damage also associated with a detonating engine. Even adding a simple "banana" style exhaust on a PK-80 can put it over the edge, falling into detonation territory, which will then lead to numerous engine problems. This was my experience. And when I started fitting "Fred Heads" onto my bike engines, all those problems simply went away. Just ask Dave from Arrow. His bikes have been excelling in the bicycle races, and since running Fred Heads, his engines are lasting for the whole race season.
You sound like a very skilled mechanic. I appreciate your input. And it sounds like you have done a nice job with your engine.
Thanks
-Fred.duh.
 
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I had the same issue...of course my studs had coarse and fine threads, so I spent days moping and miserable until I remembered threaded rod...and if there is hardened fasteners there must be hardened rod... I found some, grade 8.8 aerospace threaded rod, has an insane torque rating and some torque nuts...ive put 800 miles on her and have only rwtorqued once after 8 rides...check this section or search threaded rod head studs...
 
If you can, try and find the 12.8 grade, higher tensile strength. I had no choice but to helicoil my cases as I am running about 160 lbs cranking pressure and pulled a stud previously. Mind you the aluminum alloy in our cases is not exactly top notch. I use a custom copper head gasket and only torque to 120 inch/lbs. No leaks or issues after 3 torques total. Happened upon the 8mm hardened nuts and washers browsing a fastener place by chance one day.
 
nightcruiser said:
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That said, I wouldn't use loctite on the stud/block junction ever with the original kit studs. They are generally pretty crappy and bound to fail, extracting them from the block with loctite on the threads might be a tough job.
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You can heat the metal up a bit and the locktite softens and then you can screw it out.
 
RU12 said:
You can heat the metal up a bit and the locktite softens and then you can screw it out.
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I know heat softens up locktite, but the original studs are very weak so you do not want to loctite them in, becuase when they sheer off leaving nothing to grab onto and turn out you do not want to extract the stud while blow torching it....
 
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