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Old 12-18-2005, 12:32 PM
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Question Removal of the cylinder head studs

My question concerns the removal of the cylinder head studs in my late model A-4 in a Catalina 27, with the engine installed.

There isn't much room in the engine compartment, as it tapers to stern, but I was able to remove the intake manifold with the studs in place. Unfortunately, during the process I was not able to slide the manifold off of the studs because the rearmost end of the manifold was trapped between the narrowed bulkhead and the stud end which still extended into the manifold although a few inches of the studs were exposed.

I was able to solve this problem by pulling the rearmost two studs with vice grips, thus permitting the manifold to swing downward on the remaining stud toward the front of the engine where the compartment was much wider and allowed enough clearance to pull the manifold outward and free it from the stud.

I expect to reinstall the manifold the same way when I finish working on the valves; but, that little experience made me wonder what would have happened if I had broken one of the studs. The answer, of course, is that I would have had to remove the engine to permit access to block, and maybe haul it to a machine shop; something I would really rather not do if I can avoid it.

The next phase of the project now requires that I remove the cylinder head, and I have the same worry- what if I break a stud. I have already removed all 17 of the head nuts and, of course, the head is crusty and looks like it was welded onto the block, but I would rather leave the head studs in place if that is at all possible.

I have your overhaul manual, but I didn't see anything that offers any encouragement for removing the head in this manner. Accordingly, can you advise if it is at all possible to remove the head without pulling the studs; and, if I do break one or two of those 17 studs if I decide to pull them, can I then slap the head back on the remaining studs, torque the nuts down to 30FP and reasonably expect my A-4 to operate? Also, would you advise replacing all of those old crusty nuts with new ones? Thank you.
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Old 12-18-2005, 12:34 PM
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Don Moyer Don Moyer is offline
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The studs are tougher than you may think.

The best way to finesse the head off the studs (if that's even possible) is to keep working penetrating oil in between the studs and the head while you tap the studs sideways. Be sure to put the nut back on to protect the threads on top of the stud as you work on each one. You'll be able to tell when each of the annular spaces begins to take oil by watching it disappear down along the stud.

If you can get each of the 17 annular spaces to take oil, start tapping a common screw driver under the head from each end. At first, the tapping will create a very solid "thud" kind of sound. After the head starts to yield, and long before you will be able to see it move, the tapping sound will become noticeably more "hollow". As soon as you hear the hollow sound, continue to patiently tap and pry the head from the front and rear until it's off.

The most important mile stone will be reached when all the studs are taking penetrating oil. If any of the studs continue to fight you in terms of taking penetrating oil, it's unlikely that you'll be able to slide the head off of that particular stud. In these cases, we can usually get the stud to turn with a stud remover that grips the top of the stud by compressing down around the threads (without damaging them). Fortunately, the two studs that usually resist the most are the thermostat housing studs. In these cases, you can remove the housing and use a vise grip on the unthreaded part of the stud and remove them.

To summarize the most important part of this whole exercise: you must get each stud to take penetrating oil between it and the head, or the head will not slide off that particular stud. If you have one or two studs in this category, you may as well grip the top of the studs with a smallish pipe wrench and try to remove them (sacrificing the threads since a couple new studs are cheaper than a stud remover). In the unlikely event that the top of the stud does twist off, you can drill down through the stud to within approximately 3/8" from the top of the block, and then the head will usually slide off the remaining stud, and there is usually enough of the stud remaining to remove it with a vise grip after the head comes off. Start with a fresh new 1/8" drill bit, then 1/4", and then 3/8".

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