Disclaimer: the work I did was on a 1970 124 Sport Spider. It is probably the most simple of the twin-cam 124 engines, being 1438cc and equipped with essentially no smog equipment. A 1600 or 1800 will be slightly more complicated in that there are more components to remove from the engine during the process. I have never performed a head job on one of these later models, but I am sure if you are up to tackling this job, the removal of a few air injection valves and such will not hinder you.
It is a good idea to follow the steps in a Haynes manual or similar documentation, but it is still rather straight forward. The first item of business is to see what condition the head is in, especially if it has overheated so badly on numerous occasions as mine did. First drain the engine oil and coolant. Then remove or detach the following: the air cleaner, carburetor, timing cover, radiator, spark plugs and wires, thermostat housing, heater hoses, bolts connecting exhaust manifold to exhaust pipe, the little bolt on the exhaust manifold that holds the metal heater water tube in place, timing belt, engine temp. transmitter wires. NOTE: I found it extremely helpful to put all nuts, bolts, and washers in plastic baggies and labeling them with tape as to what they belong to (i.e. exhaust manifold to pipe, right cam tower - internal, etc.). This way you won't have to guess about which 13mm nut goes where, with what washer, and believe me, there are a lot of them!
Once all of the excess components are removed it is time to pull off the head. I left the manifolds and cam towers on, although I suppose you could remove them beforehand, it's just easier once the head is off. Remove the head bolts and have a friend help you lift the head (and whatever you left attached) off of the engine. Do it gently and carefully because you don't want to risk bending any valves. Then place the whole thing on a piece of plywood or something similar so you don't bend, scratch, or ding up anything. I even put some rags for padding underneath for extra protection.
Before doing anything else, coat the now exposed cylinder walls and cylinders with heavy grease. Rust forms unbelievably fast on these parts if they aren't protected. I used regular engine oil, but it seeped down into the oil pan over time, leaving the cylinder walls exposed, so I had to keep refilling it. The grease will burn up quickly enough when the engine is running again.
Next remove the manifolds from the head, followed by the cam towers. Remember to watch those valves. Prop up the head if you need to. I placed the cam towers on the plywood and lined up the tappets with their respective positions so that they would go back in the same way they came out. Do not remove the cam wheels from the camshafts or you will create a big hassle for yourself, as you need a special tool to align them properly to put them back on. I have been told that removal of the camshaft pulley is not a problem on later cars as there is a locating pin that relocates the pulley upon reassembly. Then you can use an old timing belt to hold the pulley while you tighten it with a torque wrench. Now store everything in a safe, clean, dry place until you are ready to put everything back together.
I didn't do any of the machine work myself. I didn't have the know-how or the facilities to do machine work, so I let the professionals handle it. I wrapped the head up in a cloth diaper to protect it and took it to my local machine shop, Marin Speed & Machine. They pressure tested the head for leaks, resurfaced it because it had warped slightly, installed 4 new exhaust valves, 8 valve guides, did a valve job, and installed a spark plug insert since the threads were stripped out of #4. For parts and labor it totaled $277.24. This was $120-150 cheaper than buying a remanufactured head. The head was also cleaner than anything on the car after the bead-blasting job they did on it. It looked like brand new.
I figured that while I was going through all of this trouble and had the engine taken apart, I might as well replace everything that I could, not just the head gasket. So I ordered an engine gasket kit, plus some breather hoses, a pan gasket, and a new timing belt. The timing belt is a must anyway. Never re-use an old one.
Now that I had the head back I was eager to put this thing back together. Despite how exciting it is to be this far along, don't rush or you're sure to forget something. The first thing to do is to put the cam towers back on and adjust the tappets just as if the head were on the car. This is vital because if the tappets aren't adjusted properly, the valves could get damaged and your valve job would go to waste, or your car just won't run properly. When adjusting the tappet clearances, be careful that the intake and exhaust valves do not contact each other. The intake and exhaust cams can move separately and valves can bang into each other, resulting in damaged valves. When you put the cam towers back on replace the cam tower gaskets and cam seals. Then put on the manifolds on with their gaskets in place. Torque down the nuts because it's difficult to do once the head is back on the block.
Replace anything you can while the head is off: gaskets, hoses, fuel lines, etc. I replaced the cam seals, cam tower gaskets, breather tubes, heater pipe gasket, and both manifold gaskets while the head was off. If you have any other work that you've been putting off because things are a pain to get to since the manifolds are in the way, now is a great time to do it. Smear some grease on the head gasket and position it on the block (Hylomar is specifically designed for use as a gasket dressing and many SCCA racers swear by it). There are some guides so that it will only go on one way. Then make sure all of the cylinders are halfway down. This will ensure that you won't damage the valves when you lower the head onto the block. Now fit the new exhaust manifold to pipe gasket onto the manifold studs. It is metal and shouldn't fall off easily. Have someone help you position the head and place it on the block. Make certain it is positioned properly and that the head gasket hasn't moved. One way to make this process easier is to obtain a couple of old head bolts and cut the hex head off of the top. Then screw the studs into the block and lower the head over the studs...fits perfectly every time. Remove the studs and then put the head bolts in. You can now attach the exhaust pipe to the manifold. Torque down all bolts to their proper settings in the proper order (as described in your manual).
Now comes the hardest part: putting the timing belt on. There is a hole in the back of the cam wheel that you line up with the raised tab on the cam tower. Line up both cam wheels so that the valves will open and close at the proper time. The crankshaft pulley should then be positioned so that cylinders 1 and 4 are at TDC. You'll have to temporarily place the timing cover on in order to do this. Then position the oil pump timing mark at about 32 degrees. Now put the timing belt in place. This involves loosening the idler pulley and moving it to maintain the proper tension on the timing belt. I had a heck of a time getting it to move, but after plenty of straining I got the belt to just barely slip on. Place the timing belt on the pulleys, making sure the "teeth" on the belt are in the respective grooves in the pulleys. Make sure the pulleys don't move during this time. The water pump pulley can move, but the timing belt should be kept tight during installation so the other pulleys don't move. Otherwise major mechanical damage could result when pistons, out of time with the valvetrain, bash into the valves. Once the timing belt has been fitted, tighten the idler pulley (there is a particular tension specified in the manual, but since mine wouldn't move much I just got it nice and snug.
Now it's time to put all of the stuff you took off the engine to get the head out back in. Make sure you reattach all electrical connections, fuel and coolant hoses, heater hoses, throttle linkage, etc. Once the engine is complete again, try to fire it up. Have no fear if it doesn't start on the first few tries. I had to reset my static timing since my distributor was off by 180 degrees, but I was worried for a minute there. Just refer to the trouble shooting section in your manual if you have problems.
Doing a head job was really quite simple now that I look back on it. I was working in my parking lot with a limited amount of tools, yet was still able to accomplish the task. The key is (as I was told by Eli) to have confidence in yourself and take things slow. Let's keep those Fiats on the road!
Special thanks to Greg and Chris for their helpful tips and info.
This page last updated: December 1, 1999
This page created: September 1, 1995