MACHINING AN ENGINE Part 2
One of the great things about this job is meeting all the interesting people who are connected some way with old cars. In the February 2003 installment of Driving Old Cars, I mentioned that our '41 Packard LeBaron Sport Brougham was the same type car used in the film "The Godfather" (part one). Soon after the issue was published, I received a call from our car buddy and subscriber Don Rook, who told us that he owns the actual "movie car". Don was nice enough to send us photos and give us some insight into what went on during the filming.
The movie "Tora, Tora, Tora" had just been made, and the CHVA (Contemporary Historic Vehicle Association) had helped supply cars for that project. When "The Godfather" was being discussed, the CHVA was again contacted to supply cars. The movie company knew exactly what kind of cars they wanted, since they had actual film footage from the 1940s depicting gangster activity. At the time of the movie's planning, Don was living in Pennsylvania, near the location in New York where the film was to be shot. The company contacted him and he agreed to supply his car, but there was one problem: The car had to have side mounts and his didn't have them. And they had to have the car in New York in 10 days! Fortunately, Don had a set of side mounts, so he put them on the car and delivered it on time. The cars used in the film were numbered. The #1 car was the black Cadillac in the scene where Marlon Brando (Don Corleone) was shot in front of the fruit stand. The #2 car was the black Buick in which Al Pacino (Michael Corleone) is driven with Virgil Sollozzo and Captain McCluskey to New Jersey and back to Manhattan for the assassination at the Italian restaurant. The #3 car was Don's Packard LeBaron. A true automobile enthusiast, Don points out the Packard craftsmanship. He says to listen closely when Clemenza closes the car door at his house (before the cannoli scene) and you'll hear TWO "precise clicks". You've gotta love this hobby!
Hearing all of this made us even more eager to get our engine back together. When we ended last month, we had installed the lifters and were ready to check valve spring pres-sure. This is done by squeezing the spring to a specific height in a spring tester, indicating pressure. Packard calls for 60-66 pounds at 1 3/4" (closed) and 135-145 pounds at 1 13/32" (open). Ours were within tolerance. Now ready to assemble the valve train, we first put in the springs with the star shaped shims on top of them. The shims are important. They are star shaped to reduce heat transfer and take up the excess space created then the valves drop lower in the seat after they are ground. With a spring compressor, we compressed the springs and installed the bottom retainers & keepers. The shims, springs and retainers have to be installed AFTER the lifters are in.
With the valve train finished, it was time to hone the cylinders. We used a pressure hone so the cylinder walls would be good and straight. We used 320 grit stones for a finish compatible with our cast iron rings. The piston walls were finished to a piston-to-wall clearance of .005-.007" This was checked by using an inside micrometer for the pistons. The ring end gap was .028'-.036", which is within the manufacturer's guidelines. We checked this by inserting the rings into the cylinders and, using a piston to push them down (this keeps the rings straight in the cylinders), we checked the gap at the top and bottom of the cylinder with a feeler gauge. Since there was no indication of a main bearing problem, we decided to leave the crankshaft in the car and not disturb the nine main bearings.
To polish the rod journals, we used 360 emery cloth with mineral spirits for lubrication, and rotated the cloth back and forth until we had achieved a smooth finish on the crank. Machining an engine can cause metal and dust particles to go everywhere. We can't emphasize strongly enough how important it is to get an engine clean before assembling it. We used a siphon blower with mineral spirits under pressure, and a lot of rags and brushes in our cleaning process.
We now moved on to reconditioning the rods, so they would be the size and roundness they originally were. We removed the rods, then ground just enough off of the ends to make the housing bore about two thousandths of an inch smaller. Then with a rod honing machine, we honed them back out to original factory specs. When we finished, we checked our bearing clearance by torquing the rods with the bearings in place, then measuring the diameter and subtracting the crankshaft diameter from the bearing diameter. This left us with a .003" clearance. We also reconditioned the small end (pin end) by pressing out the old piston pin bushings (two per rod) and pressing in new ones (one from each side to avoid covering the oil hole). Honing them on the same honing machine burnishes them at the same time (burnishing is bonding the bushing into the housing so it won't shift and block the oil hole).
Before installing the pistons, we heated them in water to 160 degrees F. Then we oiled the bushings and "palm pushed" the pins into the piston rods, making sure the slit in the piston skirt was facing the oiler hole in the rod, and installed the retaining clips, turning the bent part of the clip to face inward as it originally was. We used modern Hastings rings, which are different from original ones. Packard had a one-piece oil ring and the Hastings rings have an expander with top and bottom rails, so we used the specifications included with the Hastings rings, instead of Packard's. We put the oil rings in with the rail gaps about one inch from the end of the expander, one on either side, and opposite the split in the piston skirt (to avoid burning excessive oil as the rod oiler hole sprays oil onto the cam through the slit in the piston), then installed the compression rings with the gaps opposite each other, to avoid losing compression.
Next month, we're going to assemble and maybe even start, this engine! Keep 'em driving.