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mount on one side, putting a jack under the front of the engine and jacking, causing the engine to rise and tilt. After
one head came off, the engine was lowered, the mount reconnected, the other mount unbolted, and the engine jacked
back up so it tilted the other way to remove the other head.
David Johnson says, “It was easier for me to remove both motor mounts and lower the engine to get enough clearance.”
Johnson goes on to say that, even though he pulled the heads with the manifolds still attached, he went the other way
on reassembly. “I did that because I couldn't get 2 nuts off the bottom because some &^%%$ had galled up the threads
and the nut wouldn't come off, and the stud was trapped. Now that I replaced the studs with new, and with the ever-
present anti-seize it was much easier to put it on after.”
Whatever method is used to deal with the exhaust manifolds, make sure to take enough notes to be able to reinstall the
heads and reassemble the car.
Tip: If the tappet block is off, you may find it helpful to unscrew and remove the rear pair of cam bearing cap studs to
ease clearing things while getting the head in and out of the engine compartment.
STUCK HEADS: When you actually get to pulling the head off, if it’s never been off before you’ll probably find it
stuck. In general, being stuck means one of two things: The head and block are glued together at the gasket, or the
studs are stuck in the holes. The difference becomes evident when you actually get it loose: If it was stuck at the
gasket, then once it’s broken loose it slides easily off the rest of the way off the studs. This is typically not the case with
the V12 heads, which have metal-faced gaskets that don’t stick much, but the crud really builds up around the studs
(several of which are immersed in coolant) and makes it difficult to get the head off every bit of the way. You might
get it an inch up and still be having difficulty moving it.
This author will express an opinion here: The stuff plugging the openings around the studs is very likely the Barrs
Leaks that Jaguar recommends putting in the coolant. Heads that have been off before and never exposed to Barrs
Leaks again typically come right off without any more effort than lifting by hand. Of course, rust particles or other
deposits in the coolant might also contribute to the jamming, but careful maintenance of the coolant seems to avoid
those problems.
Loren Lingren sends this tip: “With all the nuts removed, try to wiggle the end of each stud by hand. The stuck ones
will not move. Begin soaking each stud with a good penetrating oil. Get several 7/16 SAE nuts (Don’t use the head
nuts unless you have extras) and an air hammer with a tie rod tool attachment. The idea is to vibrate the studs with the
air hammer, protecting the threads with the disposable nuts. Caution must be used not to bend the studs or gouge the
head surface. Continue to apply penetrant as work is done. As the studs loosen, the penetrant will disappear down
between the head and stud. I have used this procedure successfully for several years in removing even the most
stubborn heads, 6 or 12 cyl, without any expensive side effects.”
Other substances suggested for loosening the crud in the stud holes include oven cleaner, alloy wheel cleaner,
phosphoric acid, Nitromors, lemon juice, and Coca-Cola. Dr. Karsten Eller, chemist, says to forget about the oven
cleaner: “Oven cleaner is mainly caustic soda, i. e. NaOH. The sodium hydroxide attacks the protective alumina
coating on the aluminium and also dissolves aluminium metal:
2 Al + 2 NaOH + 6 H2O = 2 Na[Al(OH)4] + 3 H2
“Use of oven cleaner is therefore strongly dissuaded from.”
Eller says acid will be fine, however. Mike Morrin says, “Someone suggested using phosphoric acid (rust killer) as it
dissolves the rust without damaging the aluminium. He also suggested moulding little dams in plasticine to hold the
stuff around the studs.”
Regarding the use of Coke, Craig Sawyers says, “Now here's an interesting connection. Coke contains phosphoric acid
(that is why it rots your teeth).” The stuff worked just great for James Dichter: “You know it's amazing what a little
Coke will do. I'm beginning to wonder if we should be drinking this stuff. I'm also contemplating marketing it under a
different name for the purposes of unsiezing head bolts...”