Restoring your flathead

Part 6—Getting it together again—start

And the fun begins! The block is back from the machine shop along with all the balanced components. Now we have a fully restored engine, but it seems like we forgot something. What is it?? Oh yeah, it needs to be assembled, so where shall we start?

Start with the block on your rotating engine stand, wipe down and clean the interior with mineral spirits to get off all hot tank residue out of the interior and all gasket surfaces.

Time to reinstall all nine of the freeze plugs—three on each side of the lower block, two small ones on top of the block below where the intake manifold sets, and the one large one on the rear of the block behind where the camshaft goes. These should all be new and of a size that makes them a little snug before setting them. Use Aviation Permatex around the edges of the plugs, put them firmly in place and then set them permanently with a hammer.

Wipe down all the exterior surfaces that are to be painted with lacquer thinner and mask up the block ready for paint. Make sure all the internal openings are masked or plugged so that no paint gets into the internal areas of the block, including all bolt and stud openings.

Now you are ready to paint the block. I prefer the G 9540 Cadillac Green from Bill Hirsch that you have had put up in spray cans by your local paint store. Put on a light coat of paint and let sit for about a half hour. Then spray several light layers until you have a nice, even gloss. Let it dry for two or three hours and wipe down with a hard surface cloth, (i.e. bedsheet or similar) Let it cure at least overnight. After that, rub it down again with your hard surface cloth and use a very light coat of polymer wax and rub it out good. This will make it not only look great when you put it in the car, but it will also make it easier to keep clean over time. Remove all the masking tape and other coverings.

While waiting for the paint to cure, you can go to the bolt-and-nut supplier and get all of the bolts, nuts and washers you will need for reassembly. (Remember the list I told you to make as you were taking the engine apart?)

Mix up your assembly lube. I like to use a mixture of Sta-Lube Engine Assembly lube, a small amount of STP and a little bit of QX 700 Moly-Oil. You will want to coat all friction surfaces with this mixture during the assembly process.

Next you can assemble the rods, pistons and rings. Follow the ring manufacturer’s instructions and use a ring spreader rather than spiraling the rings onto the pistons. Make sure you have the rings lined up with the spaces between the ring ends staggered on the piston. Don’t forget to use your assembly lube mixture liberally.

Wipe down the interior of the block with break-in oil. It is a good idea to spray the inside of the water jacket with pure antifreeze, but make sure all the excess is drained and wiped from all areas of the engine interior and exterior where you have painted.

With the paint reasonably cured, we are ready to start actual assembly. The machine shop should have installed the cam bearings, so wipe the surfaces with a clean, dry cloth. Then smear the bearing surfaces in the engine and on the camshaft with assembly lube and install the camshaft into the block. (Remember the marks I had you put on earlier??)

After the camshaft, you can start installation of the crankshaft. With the engine upside down on the stand, clean off the journal surfaces and lay in the block halves of the main bearings. Wipe them very lightly with 3-in-1 oil, lay the shaft on the bearing surfaces in the block and spin the shaft a few times.

Insert the bearings into the bearing caps. Do not install the rear main seals at this time. Put the bearing caps on, install the bolts snugly (not torqued), spin the crankshaft a few times and remove the bolts and caps. Lay a 1-inch piece of plastic-gage on each of the shaft journals, put the bearing caps on and tighten down to 140 ft.-lbs. of torque. Do not let the shaft turn.

Remove the caps and observe the plastic-gage spread using the gauge that comes with the plastic-gage and make sure you have between .0015 and .002 clearance. If you do not have the proper clearance, follow the instructions in your service manual to correct it properly. Assuming the fit is good, clean off the plastic-gage residue.

Putting the two front main bearing caps in place is fairly simple, but the rear main cap is a little more difficult. There are two sets of seals for the rear cap. One is of a flexible, rope-like seal consisting of two pieces that fit into a groove around the shaft. The other consists of two pieces of cork approximately 3/8 inch square by 4 inches long.

Do not install these cork seals until you have the rope-like seals trimmed to a good fit. This may take several trimmings in order to get a perfect fit. When you are ready for final setdown, a small amount of Aviation Permatex on the ends is very helpful in getting a good seal.

Putting in the cork seals can be fun because of the tight fit needed. This is one of the very few places that I approve using silicone sealant. Put the silicone on the bottom and two sides of the bearing block, but only past the cork area toward the rear of the engine. WD-40 on the cork will help during the installation. Tighten the bearing block to 140-ft.-lbs. And wipe off the excess silicone. Extra time and care during this process can prevent the future headaches of a leaking rear main bearing seal.

Assuming the machine shop installed new valve guides, you are now ready to fit and install your new stainless steel valves. Set all the valves in place and check for good seating by smearing Permatex Prussian Blue on the valve where it comes in contact with the valve seat. Lightly lube the valve stem, insert the valve part way into the guide and then hit the valve into place with a sharp rap with the heel of your hand.

Do not move or rotate the valve but push the valve up out of the guide from below and lift out the valve by the stem, being careful not to touch the face itself. Inspect the seat areas on both the block and valve surfaces. Be sure the impression left in the Prussian blue is nice and even. If not, use a bit of valve grinding compound and a hand grinding tool to smooth out the surfaces. Repeat the processes again until you end up with the smooth, even surface. Clean off all of the blue and grinding compound from the valve and block.

Now it is time to check and set the valve stem length. Using a T-type tool or telescoping gage, set exactly at 3.000 inches for this procedure. Turn the cam lobe under the valve you are working onto the position furthest from the bottom of the stem. Then put your gage between the cam and the bottom of the stem and press the valve down to see how much you need to grind and/or file from the bottom of the valve stem. Clamp a guide onto your grinding wheel to make sure you grind down smooth and flat. Take off just a little at a time until the gage is snug and the valve face is snug against the block.

Doing this right can make a lot of difference in the smoothness of the engine later. When you have a good fit, slightly camphor the end of the valve stem and polish the end on your buffing wheel. Put the valve into the block, assemble the upper and lower valve spring seats onto the valve guide and valve. Using a valve spring compressor, compress the valve spring into place and set the two half-moon keepers (locks) into the slots on the bottom of the stem and slowly release the pressure on the compressor. A little trick here to help you is to use a small amount of axle grease to hold the keepers in place. This may take a few tries until you get the hang of it.

OK, good job. Now repeat the process on the other 15 valves. When done, take a crowbar, compress each valve spring to make sure all of them have seated well. Now take your gage and check to make sure you have the final 3.000 clearance on each valve. If you have a valve or two that is too long, remove it, file down a little more, then reassemble and check again. Is everything right now? Good. Let’s go on to the next step.

Putting in the four lifter gang assemblies will be a lot easier if you kept those little rubber pads I had you make to take these gangs out. Using a crowbar, lift up the four valves and insert the rubber pieces, making all four valves stay open about 1/4 inch. Carefully set the gang in place without forcing it. If you need to, you can rotate the cam a bit until the gang slips into place.

Take one of the sheet metal strips you made when taking these apart, put your bolts (new ones, I hope) through this strip, through the gang and into the block. Run the bolts down a ways with your finger and then jiggle them to make sure they settle into place. Torque them down to 50 ft.-lbs.

Then bend over the corners of the metal strips onto the bolt head to hold the gangs in place. You cannot use lock washers here, due to the constant vibrations of the valve openings and closings. Repeat this process for the other three gang assemblies. You can install the splash pans, but leave the “T” oil lines off until later when you can bleed them with oil in the crankcase.

It would be a good time to install the oil line from the side of the block up to the angle fitting between the two freeze plugs on the top of the engine. I recommend forming a new steel line with fittings using the old one for a pattern.

Next month, we will continue by putting in the rods and pistons and go on to complete the assembly of your new engine. In the meantime, sit back and admire your handiwork so far. Maybe even show off your progress to a few friends and fellow Club members over a cool beer. Skol!

See ya next month,

—Walt