On the heels of the 0-ring topic, here comes the head gasket. This topic is like art, it has to be done a certain way and everyone has a spin on what works for them. Let me say up front that after doing a lot of head gaskets, my success rate is pretty high. What I do is just plain simple “cleanliness” when doing a head gasket. This is written so that it covers not only 1300/1600, but also 1750/2000 engines.
The most obvious fact about doing a head gasket is to get the head off and determine why you are doing all of this labor. Most times it is because the head gasket failed due to leaking out the sides on a cold start. Anti-freeze or oil will run down the block in streaks until the block heats up enough to seal the surfaces. Usually this is caused by the head not being properly torqued, re-torqued or rechecked. The head gets a tad loose and the sealing surface gets wide and the fluids find the path of least resistance. One morning you come out and there is a puddle of anti-freeze or oil under your car you haven’t noticed before that is probably bigger than usual. You take your index finger, touch it, inspect it and “wallah!” its fluid.
Take the head off. I won’t go into a long discussion on how to remove the head as there are several books and threads on the Alfa Bulletin Board. Now here is where it gets crazy. What if the head doesn’t want to come off? Everything is loose, including the two bolts under the head. You have popped it loose just a hair to break the gasket seal, yet it won’t go more than an inch. Ok. What gives? It is stud corrosion! Yes, the insidious stud corrosion that comes from gunk and rust building up on the studs inside the head passages to where it is so thick you can’t get the head to move. Solution: Lots of spray carburetor cleaner, and PB Blaster soaking down around the stud holes. After letting this soak in for a day applying liberal amounts, the crud should soften up enough that you can begin to move the head. It won’t come easy, but it will lift off. Just be sure you go up and down, and it will come off. Worst case for me was to get a 2×4 and lever it in between the block and head to push up on the cylinder head. I have heard of one case that the head wouldn’t come off, the engine had to be pulled and replaced. Yes, it was that bad.
Install some liner holders so that the liners don’t move and break the seal on the bottom of the liner and block. Trust me, you don’t want the liners to move! You can use some large washers, metal tubing, more washers on top and the “acorn” nut to hold it all in place. Just make the nut tight (about 10-15 ft lbs) to hold it in place.
Now that you have the head off, look at the head gasket and inspect the o-rings. Are they nice and round? Deformed? Hard or soft? If they are soft, most likely they are Viton or some material like it. Look at the sealing surfaces and see if you can find where the leak was coming from. If it was a blown head gasket due to a weak spot or over heating, see if you can spot it. Usually it is a dark spot between the cylinders or out towards a water jacket hole.
Peel the gasket off and toss. Sometimes it just lifts off leaving very little behind .Other times it will be a pulling affair to remove it, leaving lots of material to clean up.
When you do get the head off, check it for flatness using a machined straight edge and feeler guages. When you lay the straight edge on the head you should see no light under the metal. Measure and you should get zero (0) to .002 thousands clearance. Any more and you will have to mill the head for a skim cut.
Something you will notice when you get the head gasket off is the corrosion around the stud holes. This is normal electrolysis and milling the head down to remove it only wastes life of the head. Welding is expensive, so save your dollars. As long as the corrosion doesn’t effect any of the sealing surfaces, just leave it. What you do want to look for is cracks in the aluminum. If you want, take it to a machine shop and have it dye penetrated for cracks. Cracks can occur generally between the water jacket and a valve seat. This can be repaired with welding and a new valve seat.
Ok, here is your list of tools and supplies you will need:
- Carburetor cleaner or acetone
- Gasket scraper – wide face
- Pipe cleaners – large
- 800 grit wet/dry sand paper
- Clean rags and/or paper towels
Install the pipe cleaners into the oil passages. Leave about a 1/3 sticking out of the hole and bend over so it doesn’t slide down in the passage. This will help you from getting head gasket material down in the oil passage! Put some rags or paper towels in the chain galley to keep junk from falling down into the oil sump. Want to guess where that will wind up? (see the end of the article *)
Soak the mating surface of the head and block with the carburetor cleaner/acetone. Allow for adequate ventilation. Let sit until the gasket material turns soft or continue to soak with fluid until it does. You do not want to force the material to come loose as we are dealing with aluminum. Any scratches or deep marks is not a good thing on a sealing surface. Gently use the gasket scraper to push the gasket material off the head and block. Do not push down hard, if you are pushing hard you need to soak more. Most of the gasket material will just come right off if you have worked it correctly leaving behind a brownish or grey colored residue.
On the block you can use an Exacto knife, single edge razor blade or something sharp to clean around the locating studs for the head and head gasket. Do not use it anywhere else! This will let you get the minute stuff that you can’t get with the gasket scraper.
Now that you have all of the gasket material off, you are now going to spray the carburetor cleaner on the block and cylinder head to make it wet. Using the 800 grit paper, you will “lightly polish” off the rest of the gasket material until you have a nice clean shiny surface for the new gasket to seal to. Remember this is what the gasket will stick to, cleaner surface the better the seal. Do not overly push as you can leave depressions or wave marks in the surface of the soft aluminum. If you have a small wood block to wrap the paper around that would be a good way to make sure it is level when you polish.
If you sent the head out for repairs, most likely it will come back with a skim cut which should be very fine in appearance or hot tanked leaving a nice clean head you don’t have to mess with until your ready to install the head gasket. Shown below is a before and after shot of what your head should look like.
Using the acetone or carburetor cleaner, use some tissues to do a final wipe down of all the surfaces taking off all oil residue. Remove the pipe cleaners and rags in the chain galley.
Before I go any further, I only put sealant on the back part of the head gasket as per my note below. There are some who will spray gasket sealer on both sides of the head gasket to insure sealing. I have seen Permatex copper sealant used. If you use a gasket that has
no sealant properties on it, then this is great stuff. A Reinz or Victor gasket will usually have a sealant applied to the head gasket. Your choice…use it or not.
Put the head gasket in place, making sure it lies flat on the block and in place with the locating studs. Install the o-rings in to their respective holes (see previous article on o-rings). Slide the head onto the studs and lower gently until the head is sitting on the locating studs or all the way down. The rest is by the book.
While the head has been soaking in cleaner to loosen the head gasket material, I get a sheet of the 800 grit paper, some water, a flat surface like a glass pane and sand both sides of the washers till they are flat again. I also do the same to the bottom of the acorn nuts so they are flat as well. This insures a even torque on the stud, washer face and a clean sealing surface so there are no leaks of coolant around the studs.
Some like to use fresh oil as per the factory book to lubricate the acorn nuts and studs when installing. I prefer to use aluminum anti-seize compound as it just makes it easier to come off next time. Oil can turn to carbon and become sticky or hard, making removal difficult.
Torque is essential and in the correct order. I usually start with 25 ft/lbs, go to 40 ft/lbs, and then torque to final ft/lbs. This way I get a gentle crush on the gasket and o-rings.
In closing there are two more points that are important to remember. Some of the new gaskets do not have sealer around the back of the block crank case ventilation holes in the head. You must use some high temperature gasket sealer on these surfaces or area.
The 2nd point is that you re-torque the head after the engine has fully warmed up to temperature. Back off a 1/4 turn and torque to final value again. I let it sit over night and check torque, but I don’t back off the nut. If you have no movement your good to go. After 500 miles re-torque again by checking. Some say to back off a 1/4 turn and then reset. I just check them for proper torque.
I am hoping I covered all the important points and why I have good success with head gaskets not leaking. If I forgot a step or you have a hint/trick that works for you, let me know and I will drop it into a the article.
* it winds up in the oil pump screen, in the oil pump, oil filter and who knows where else*