If everything looks in order after a cursory cleaning, it’s time to get your hands dirty. You can never have enough pictures of this assembly because every shim, every washer, every spring, and every rocker needs to be assembled in the exact order it was taken apart.
If the parts are simply sitting in a box, reconstruct the assembly to make sure that you have all the parts and everything is serviceable. Once complete, take a picture, so you have a template on how to put it back together. You can also refer to the photo in the shop manual.
This engine is the newer-style 235 with a center-flow spout that has no second tube coming out and looping back to the bottom of the assembly. This newer style puts all the upper engine oil flow through the rocker assembly shaft system before dumping it back into the reservoir.
Cleaning
Here too, you need to clean things thoroughly before even thinking about a successful assembly. Too often, cleaning reveals something you need to address. In this case, I go out of my way to ensure that this assembly is perfectly clean. To do this, you really want to take it apart carefully and place components in the proper order. In this example, two rocker shafts meet in the middle. Once disassembled, these two shafts need to be inspected carefully for excessive wear. It’s very common for these rocker shafts to be considerably worn where the rockers move on them. It’s worse when there is no oil reaching the rockers. In this engine, both shafts have very little wear and look really good for their age.
Take about a 14-inch piece of 3/8-inch steel rod and push it all the way through the inside of the shaft. Do it very slowly and knock off all the crud with a small screwdriver (or similar) as you go past each hole. Use your parts washer’s pump action to push kerosene through the shaft. Repeat this until the kerosene comes out clean.
This style of rocker assembly (the newer style) has no oil-return pipe. All of the oil going to the upper end goes through the rocker shaft assembly before being dumped back out into the reservoir.
On the outside, use double-O steel wool to make sure the entire surface is perfectly smooth. Don’t expect to remove all the stains, but do clean it thoroughly. Don’t use an aggressive grinding wire wheel for this. You need to keep as much of the finish as possible. Do not sandblast the shaft.
You need to clean all the rocker assembly parts. First run them through the kerosene wash, use a wire brush, dry them off, then remove the pushrod contact assembly from the rocker arms. You want to thoroughly inspect the ball that comes in contact with the pushrods to ensure that there is no damage or excessive wear. You also do not want to damage that part of the rocker. Once apart, clean the rockers including the valve contact area with kerosene and light oil.
This super cleaning was accomplished by taping all machined surfaces with masking tape then bead blasting the outside of each rocker. Don’t forget to chase all the passages and clean thoroughly after blasting.
You want to clean each rocker thoroughly. Chase the threads, use a piece of safety wire or a paper clip to clean the oil hole. Once blasted, run some 400-grit sandpaper through the shaft hole, on the flats of everything. When assembling, remember that the shaft’s oil holes face downward. Once the entire assembly has been cleaned, put it back on the head to make sure each rocker contacts the valves exactly in the middle. Once you are happy with the cleaning job, spray some WD-40 all over the assembly to keep the rust at bay during the rest of the project. Set the assembly aside.
I like to leave about three threads showing on the rockers. This is a good neutral position for the valve adjustment procedure later. As this rebuild progresses, you will be glad you addressed these issues before going to the engine machine shop. Had any lifters or rods been damaged or you want a second opinion, you will have this information beforehand.
Head Machining Prep
You will save money and time at the machine shop if you remove the valves beforehand. One threaded plug needs to be removed and saved for later, and to make life easier for the machine shop, also take out the valves. You must do this at least once to appreciate how badly these valves can become abused.
To remove the valves, you need a valve spring compressor similar to the one in the tools list. You may prefer a throat about an inch longer.
The rocker assembly is now ready for the finished head. Spray the outside of any super clean assembly with WD-40 to keep things from rusting.
With everything cleaned and working like new, you can set the whole assembly aside awaiting the finished head. Notice how the WD-40 brings out the shininess and makes it look normal again.
Be careful with the spring compressor. Lock the handle, then turn the crank handle, making sure you are solidly on the valve on one end and centered on the spring on the other. Once you turn the screw sufficiently, the keepers either fall out or can be retrieved with a small screwdriver. Break the plastic retainer and then let pressure off the spring the same way. The spring should safely come out, and the valve should slip out as well. If it doesn’t, I use the handle end of my hammer to tap it a little.
This is where you need to get to before you send the head to the machine shop. Everything must be removed. You will not be reusing the valves, and if the springs do not meet specs (as ascertained by the machine shop), they will be replaced too.
Be sure to remove all plugs and fittings. Take it easy on the temperature sensor on top of the head. That fitting is very difficult to find. It is not a standard NPT size on pre-1955 vehicles.
Once compressed, the keepers almost fall out. Carefully remove the keepers, then do it 11 more times.
Place the valve spring compressor carefully in the center of the valve shaft. It is not as dangerous as with the suspension of a car, but always think safety first when removing springs under load.
Damage from a poor-running engine looks like this. This engine is in need of a valve job. It never ceases to amaze me how these engines run anyway, despite the damage to a point.
All of this crud was attached to the valve. Something went terribly wrong. Discoloration of the metal proves that something was causing them to become abnormally hot.
Be sure to remove any fittings on the head. When the engine shop cleans the head, the techs can do a better job with everything removed. If you cannot remove a fitting, let the shop know.