Brennan I.M.P.

Under Roy Evans, the American Austin and American Bantam companies exploited any opportunity to maximize cash flow.  The Brennan IMP is one of these opportunities which was seized onto.  In 1936, the Syracuse based Brennan Motor MFG. Co. introduce the Brennan IMP.  It was a year or so after American Austin ceased the production of cars and about a year and a half before American Bantam Began.  When Bantam reorganized and began production, its engines were altered enough to avoid paying royalties to Austin.  In a brilliant idea, it is likely that Bantam liquidated its remaining American Austin engines and a plethora of parts.  The eager buyer, Brennan.  While the pacific pumper utilized the Bantam Engine, and an early Lawrence water pump did as well, no other company forged the relationship with Bantam that Brennan did.

When Bantam began production in 1937, the output of the Brennan matched its automotive counterpart.  At this point, the Brennan was basically a standard automotive engine with a proprietary marine transmission mounted to the flywheel end.  Over the next three years, the Brennan appeared to accept each improvement that Bantam made to its engines, but at a slower adoption rate; almost as if Bantam used Brennan as a way to get its more obsolete engines out of the factory.  First moving to a pressurized lubrication crank shaft and later adopting the three main bearing crank shaft.  One existing Bantam based three main Brennan engine is known to exist and it has a serial number much higher than any of the engines recorded as installed in cars from the factory

Although the date of transition cannot be pinpointed, Brennan began manufacturing a new IMP, this engine having a proprietary crank case with a transmission mounting at the front of the engine.  It appears that this change happened some time between 1941 and 1944.  The most likely cause for this transition was necessity.  In 1940, the TENUAL factory which produced several aluminum parts for Bantam engines was badly damaged by a major fire.  Many manufacturers lost their engine tooling in this fire, and with World War II on the horizon, most manufacturers did not end up investing in such tooling.

An engine believed to be the prototype (or at least a very early) Brennan Imp with a proprietary crank case has survived.  This engine has a standard Bantam cast iron head where the water outlet has been milled off and blocked with a blank plate, a standard Bantam 3 main bearing block with  the correct casting numbers for such an engine, and a Tillotson M10BX carburetor.  With this engine, Brennan introduced a stronger IMP having removable bearing caps and insert bearings.  This is the version that would be tweaked at least through 1968 to be capable of putting out 40 hp.  If you notice, the primary way Brennan extracted more power was through spinning the engine faster.

Brennan Motor MFG., Co. closed its doors in 1972; likely building the IMP all the way until the end.  The IMP allowed the Bantam engine to survive an extra 32 years.  Unfortunately, not very many Bantam enthusiasts took advantage of the fact that new parts were available in the early days of the clubs.  However, without the internet and the fantastic resources that are available today, it’s easy to see how many may never have even known that such a company existed.

If you know of any Brennan IMP engines, please do your best to make sure they don’t get scrapped.

Below are all of the available Brennan IMP advertisements and magazine write-ups that I have been able to discover.  Enjoy following their evolution from 15 to 40 hp.

1936 – 15 hp – Introducing Brennan “IMP”


20 HP Brennan Factory Brochure:

20 HP Vintage Ads

25 HP Brennan Factory Brochure (Circa 1944):

25 HP Vintage Ads

27 HP Vintage Ads

30 HP Brennan Factory Brochure (Circa 1958):

30 HP Vintage Ads

35 HP Vintage Ads

40 HP Vintage Ads


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