Removing Ferrari Cylinder Heads
The cylinder heads of Ferrari V-12 engines have a well deserved reputation for being challenging to remove. This difficulty is primarily due to the very close tolerances between the head studs and the head, with a small contribution from the head gasket. Over time, these steel studs corrode the aluminum head, bonding the two together with significant strength.
I had previously decided to rebuild my 330 engine, so it was already out and on the stand, with the distributors, carbs, and exhaust headers removed. I felt it wise to remove the camshafts first, to avoid any risk of damage to them. This was accomplished by first removing the cam chain sprockets, then removing the rocker arm assemblies. There are six of these assemblies per cam, and I started by taking off the unloaded assemblies first. At one point, the camshaft was rotated by those springs still in compression, so watch those fingers!
Once the camshaft and rocker arm assemblies were off, I removed the large front cam chain assembly. It turns out this isn't necessary for removal of the heads, as there were no intersecting parts, just recessed rubber gaskets for the coolant inlets.
Ever the optimist, I tackled the first head by firmly grasping it with both hands and tugging smartly. This accomplished exactly what you'd expect - absolutely nothing.
So I went to Plan B: Hit it with a rubber mallet... but non too enthusiastically really, as I didn't want to break or bend anything! This was not as adventurous as it seems, as most everything else had popped free easily with a gentle tap. Hoping it was just the gasket holding it on, I tried to persuade it from the ends and the middle. This also accomplished exactly what you'd expect - again absolutely nothing. One thing I had been cautioned against was trying to pry them loose, as the aluminum is relatively soft, and any damage to the head or block guarantees the need for more expensive machining work. The literature even suggested using wedges hammered in to raise the heads, but I had no desire to try that either.
So on to Plan C: Make a puller. Used by many Ferrari shops, this tool pulls the head up by the rocker arm studs, by pushing down on the head studs. I made my head puller out of some old board I had lying around. It was 1/2 inch solid Oak, which seemed stout enough at the time, with aluminum strips epoxied across the grain. The holes were located simply by lining up and marking using the head, and were drilled slightly oversized. BTW, the holes are not symmetrical, top to bottom and side to side, so don't make any assumptions.
I used 3/8 inch carriage bolts to push down on the head studs, as they have the threads their complete length, and would ultimately fit deep into the head pushing each stud. I dressed the bolt tips flat on the disk grinder, so the head studs would not be damaged. As these carriage bolts were fixed in height by their nuts, I turned the cam rocker nuts to make it work, meaning I had to adjust the carriage bolts every 1/4 inch as the nuts bottomed out. A shop puller would have these bolts threaded into the tool, so the bolts get turned - MUCH more efficient to use, but requiring greater precision and higher cost to make.
A good clean around the head gaskets was done, and the puller assembled onto the head shimmed up above the spring keepers, to give room to pull the head up to the board. The carriage bolts were made tight between each head stud and the board, with the top nut there to stop them from moving around. This part actually worked out OK.
The studs where hosed down with penetrating fluid, and after increasingly tightening down on the cam studs, a tiny gap opened up around the gasket at one end of the head. I got my hopes up, but after that all the wood did was pop, compress, and bend. Adding nuts to the rest of the cam studs didn't help, and even the metal strips started to bend and separate from the wood. Tom Yang brought up a very good caution about the wood letting go and leaving only part of the head under stress, with the attendant chance of cracking the head: At that point I got spooked and pulled the wood off the motor. I still say the design was sound, albeit a bit 'shadetree', but that wood was no match for 36 years of corrosion.
So on to Plan D: Make a better puller. My good friend Bill White had long ago offered to make the puller from steel, so I took him up on it. Using the wooden one as a template, this one is in 1/2 inch cold rolled steel (heavy!) and has carriage bolts on all the head studs (Thanks Bill!). Bill said he can make these up for anyone who is interested.
I started with a little torque on all the rocker nuts (spiraling from the center out), and eventually ended up working each head off a 1/8 turn at a time, adjusting the carriage bolts 1/4 inch again every time the nuts bottomed out. Patience was needed, and each head wanted to come up crooked. I ended up working the nuts more on one end than the other, eyeballing and measuring the gap often to keep it even. The initial 4 1/2 inch cariage bolts ran out of thread and had to be replaced with 6 inch ones, as the darn heads fought me all the way to the very top of the head studs (don't drop it!). Interestingly, both heads are the *same* unsymetrical casting - I expected to have to flip the puller over for the opposite head, but this wasn't necessary.
Both heads came off without any damage, and what was found is a story for another day. Fwiw, the head studs did not appear corroded, it looks to be just the aluminum. You can see this as white powder in the head stud threads in the picture above. The first head took a couple of weeks altogether, working on it during spare evenings. The second one took 4 uninterrupted hours one Sunday, so it can easily be done by one person. Given the configuration, I'll wager it could be done IN the car too, if the need arose. Good luck! If anyone has any questions/comments, I can be reached at the address below.
Preceding Page | | HOME | | Next Page
Revised: March 5, 2002 Copyright © 2002 Jonathon Brent