Restoring your flathead

Part 5—Block preparation

As you look over your tables of restored parts with pride, the block itself is just about ready for the machine shop. However, there is still a bit of work to do to make the block ready for that trip.

Start by taking out the freeze plugs. This is really rather simple. First, drill a small hole in the center of each plug (there are three on each side of the block and two smaller ones on top between the valve lifter cavities), and using a small slide hammer designed for removing dents, screw it into the small hole and tap out each plug. If a slide hammer is not in your toolbox, use a cutoff tool or Dremel to cut a slot into the plugs and pry them out with a screwdriver.

Be careful not to damage the block itself. There is a block drain low on each side of the block. These may be ordinary pipe plugs but should actually be small petcocks. Remove them and replace with new later.

Also take out all of the external oil fittings and the plugs covering the ends of the oil ports. You should now have a completely bare block that is ready for a very thorough cleaning.

If you don’t have a pressure washer, you may want to rent one. Of course, the option is open to take the whole thing on the stand to a coin-operated car wash. Clean it thoroughly inside and out, and flush out the inside of the water jacket by directing the stream into each of the head bolt holes, the holes where the freeze plugs came out of, and every other opening you can find. You will be amazed at all the guck and grime that comes out.

Make several rounds of doing this until all you get is clear water from every location. Wipe and dry the whole block using compressed air and/or rags. Make sure all of the oil ports are cleaned thoroughly using your various shotgun and rifle cleaning brushes.

Now is your opportunity to inspect the block for flaws. I will share a little secret here with club members that is quite a bit cheaper than the Magnaflux or Zyglo processes. Start around the cylinder walls and valve openings. Clean and wipe down the area with lacquer thinner, making sure these areas are real clean. Put on your latex gloves and paint the area around the cylinder walls and valve openings with black shoe and leather dye.

After it has dried, use fine (No. 000) steel wool to clean up the surfaces and valve areas and wipe down with a dry, clean cloth. Now inspect with a bright light and magnifying glass. If there are any cracks, they will show up clearly. These can be repaired or plugged by any good machine shop.

The same basic process can be used on the cylinder walls, except that you lightly use a fine cylinder hone and wipe with a dry cloth. If there are cracks in the cylinder wall, it is a bit more serious and will require a sleeve to be installed. At this point, if cracks are severe or multiple, you may want to find another block and start over. Better to find out now than after completing your rebuild and driving for a few miles with perpetual heating problems.

The exterior is a little easier to check out using bright lights and a magnifying glass. If there is any place that is questionable, you can use the black dye process to be sure. More than likely, your block is in good shape and we can proceed. Let’s hope so, anyway.

Porting the block can increase horsepower and efficiency by 10 to 20 percent if done right and now is the time to do it. What this consists of is grinding out the ports between the intake valve seat and the cylinder wall. This is a touchy procedure and you might decide to let your machine shop do this, especially if you have never participated in this procedure.

The big moment has arrived—time to load the block, crankshaft, camshaft, main bearing caps, flywheel and clutch pressure plate for the trip to the machine shop. Once your machinist has bored the block and turned the crankshaft, you will know the right sizes to order for the new pistons, rings, main bearings, rod bearings and camshaft bearings. It is a good idea to also order new rod bushings.

While waiting for the machinist to give you the needed sizes, it is time to clean up the rods. They need to be extra clean to be ready for balancing. Don’t forget to clean out the oil ports in these rods. Large pipe cleaners from craft and hobby stores work real well for this.

When UPS or FedEx brings you the parts, they can be rushed to the machine shop for balancing along with all the other parts already there.

Let’s talk again for a minute about balancing. I mentioned in a previous article about balancing, but at the risk of repeating myself, I want to remind you that a good balancing can improve performance and smoothness beyond your wildest imagination. The technology of today in this field is so very far advanced from the days when these great flatheads were new.

A partial balancing will help some, but unless you go all the way, it would be a little like going to a Cadillac-LaSalle Club Grand National or tour with the idea of starting a strict diet. You won’t starve, you will have some fun and save some money, but, you will sure get a lot more enjoyment if you do it up right.

The parts the machinist will need to give you a real good balance (in addition to all the ones he already has) will be the rods and bushings, the front pulley, assembly and vibration damper and the balance of the clutch assembly. He will balance all the parts in harmony with each other as well as individually.

We can take a few days off now until everything comes back from the machine shop. We’ll see everybody next month when the real fun begins as our flathead goes back together. Martini, anyone?

—Walt