Autopsy of an American Bantam Engine, Part I:

The odometer only shows 37,000 miles or so.  The frame looks like new.  The sheet metal isn’t even that beaten up.  So what happened to this car?

I had the chance to pick up some parts from an early 1938 coupe this weekend and with it was an engine.  I had known about this car when it had first hit craigslist and ebay about a year ago.  In the interim, a person bought it to build a hotrod from the body and was looking to sell the rest of the parts to make room for his project.

As you know, Bantam engines have a reputations for crankshaft problems, and I was thinking that with everything presenting as it was, perhaps crankshaft failure was the reason for this car’s premature parking.  Looking at the crank case, I saw it was obliterated, but wasn’t sure what else was wrong with the engine. I got the engine home to find the flywheel turned, but not all of the way around.  Even though it was late, disassembly began.


Finally home and waiting for disassembly

As you can see, the entire back of the crank case is destroyed where the cast in bell housing meets up with the cast iron bellhousing adapter on the transmission.  Even more strange is that a large ring is entirely missing from the flywheel just aft of the ring gear.  Without this ring, there is no way to mount a Bantam clutch assembly to this engine.  If you look at the corner of the oil pan, you can look right into the engine.


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With the pan opened up, the crankshaft became visible as did one of the reasons the engine wouldn’t turn.  The rod bolt for piston 4 was interfering with the bracket for the oil jet.  Also visible are signs of welding on the oil dippers integral with the caps and shims, possibly indicating a rebabbitted engine.

Further inspection shows that this engine had blown up at one point as there is a lot of damage to the crank case which has been welded up.  Presumptively, someone was hoping to bring this engine back to life, and forgot to tighten one screw all the way.  The flywheel that came with the engine was rubbing on the back of the block as a spacer was missing, but placing a different flywheel assembly on the rear alleviated that issue.  If you look, you can see the difference between a correct flywheel and one that has been heavily damaged.

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Every aluminum part on this engine, except for the intake and carb are damaged.  There is no doubt that this engine had a hard life.  It’s actually amazing that the intake and carb have survived as they are most often broken off while all of the other pieces are fine.

In order to take the crankshaft out, which is the ultimate goal, I need to take quite a few parts off of the engine.  Taking the pistons out revealed a crankshaft with very nice looking journals and an odd assembly of rods.  This engine has two rods marked number 1 and no number 4.  Each rod has had a number of lines filed into the beam indicating which cylinder it corresponds to and attempts to cover up the original markings are present.  Two of the rods are part number:  A -3677 while the other two are A -3677 X which markings are quite different from the others.

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The cylinder block looks quite nice upon closer inspection.  Here are a few miscellaneous photos highlighting the condition of this engine.

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Although I was hopeful that this engine would have shown itself to be in better condition when I picked it up, all is not lost.  There are some really great parts on this engine that may either allow an entire other engine to be rebuilt (if the crank comes back good), or a bunch of parts that may help several other engines get back together.

The next installment will show the removal of the crankshaft and further disassembly.


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