Re: 1948 Limo Super 8

Posted by DavidPackard On 2021/12/31 12:42:29

Hi Duane
Nice car to take the ‘little Gunn’s’ for a ride!

I’m assuming this is the first time you’re trying to start the engine . . . the list is a bit longer if that’s the case. Yes a slow cranking speed can hamper starting, but with a fresh rebuilt engine that may be nothing more than a bit extra drag. Did the engine rotate freely following the rebuild? Perhaps a squirt of oil into each cylinder is in order as you trouble shoot the crank speed issue.

Battery: I would start the trouble shooting with the battery. I’ve had pretty good success with a NAPA group 3EH battery in my ’48. The downside it is an old school wet battery, so all of the memories of corrosion will come ‘flooding’ back, but the up side is the large capacity . . . close to 1000 amps available. My ’54 has an Optima six volt battery, and that seems to work quite satisfactory. A quick test on whether the battery is part of the problem is to jump with a known good unit, but only after you charge both the battery that is in the car, and the other battery as well.

Cables: I hail from ‘Double Aughtville’, with soldered terminals no less. I’ve been looking for a 00 braded ground strap, but never did find one, so I had to use ‘round wire’ for a ground. I used welding cable (more conduction area) as battery cable material.

Ground Path: As far as I know the current return is into the round portion of the starter case, and then into the nose piece. From there the current path is the bell housing, engine block, and the ground strap mounted near the generator bracket . . . lots of opportunities for voltage drop. I found my ’48 had a good amount of paint (thanks to previous owners Tom and Marvin) applied to the bellhousing where the starter mounts. I believe the design intent is a clean dry surface at this location. My ’54 had so much oil (rear main seal leakage) there; it’s hard to believe that any current could pass to the bellhousing. You mentioned a fresh rebuild of the engine, did that include a fresh ‘paint job’? Others swear-by a second ground path from a starter bolt to the chassis, and then from the chassis to the same location where the battery ground cable is attached. The pre-cautionary advice is to make sure if you use a different bolt at the starter that new bolt length does not come close to the flywheel.

Starter: You mentioned a rebuilt starter, so I would assume that’s OK, but a few checks may be in order. Commutator cleanliness, brush contact pressure, and bushing health are the items I would check. Another ‘off-the-wall’ comment is: The only difference between a ‘stock’ six volt starter, and one that has been converted to twelve volts are the field windings . . . quite interchangeable! The local custom for the ‘Brand X’ crowd is to paint the armature shaft red if the starter was converted to twelve volts. I think you have the opportunity to check a few items by removing the starter motor for a quick bench inspection of the starter, plus the bellhousing. Other members may help us understand whether a converted starter can be detected with a simple resistance check . . . again that’s just an ‘off-the-wall’ comment, but the previous owner’s intent may have been to convert the car to twelve volts.

Solenoid: If I remember correctly the solenoid design during those years did not allow for the inspection of the contact surfaces. If you decide to remove the starter, you could power the solenoid and measure the resistance at the post intended for high current. You must take some care as to avoid placing the multi-meter in the powered load path.

It took a while, but both my ’48 288, and the ’54 327 crank at a respectable speed. I would say the cranking speed is what you would expect in a twelve volt car from the same era.
dp