"A Straight 8 Comes Together" - Part 10
We're continuing work on our '36 Packard Coupe project. As we ended last month, we had a miss and backfiring through the tailpipe when at an idle. We had rebuilt the carburetor, distributor and vacuum advance and checked all vacuum lines.
This car has a Bijur lubrication system that works off vacuum and pressure feeds grease to the grease fittings upon starting the car. It also has a power brake booster and a valve for the mechanical brakes. Our problem turned out to be the booster valve. These valves can be rebuilt by disassembling them and cutting a new gasket from gas & oil resistant material. This fixed our problem and now the car idles quietly and smoothly.
With all systems checking out, we are at the test driving stage now. We are driving the car on short, in-town trips and then back to the garage to go bumper to bumper, checking and adjusting until everything works correctly. I have been fortunate over the years to find many of the old motors and electrical manuals which are really helpful when going through this engine. Here are some engine troubleshooting tips that have helped me:
Connecting Rod Noises: This light knocking sound is most heard when the car is running at a moderate speed and the accelerator is eased off. To locate the worn bearing, short out the spark plug wires one at a time. The noise will be less when that cylinder is not firing.
Valve Train Noise: A clicking sound that increases with engine speed and seems to disappear with higher revs is caused by excessive valve clearance on solid lifters, or defective hydraulic valve lifters. Our '36 uses solid lifters and after our valve job, we adjusted all valves cold, then ran the engine and re-adjusted them hot, drove the car and re-adjusted them again-before getting them right!
Crankshaft Noise: This is a heavy knock that can be felt through the accelerator pedal. It can also be felt at an idle, but is most noticeable when the engine is pulling under load.
Piston Pin Noise: Most often heard when the engine is idling. It is a metallic sound and is a result of worn or loose piston pins, or worn bushings.
These are some abbreviated engine checks, and we will go into this more as we road test the '36, which we plan to do during the Christmas Holidays. This year, we have seen many of our projects come together, thanks to our "old car buddies". We feel fortunate to be in a profession where people still work together to make things happen and have fun doing it. We appreciate you and wish you and your families a very Happy Holiday Season!