This is a rare Bristol BS1 Mk3 competition engine, it’s thought that just 60 or 70 of these were made in period and few are known to survive today. Though it looks like a double overhead cam design, the unusual engine actually has just a single cam in the block.
The 2.0 liter inline-six design was used under license from BMW after WWII as war reparations, and it powered many Bristol cars well into the 1960s. In standard trim it was good for 80 bhp at 4,500 rpm, a reasonable figure for the time, but in racing tune it was capable of 140+ bhp.
When viewed from the front or rear, the engine can tend to trick people into thinking it has double overhead cams.
Aviation and military history buffs will already know the name Bristol well, as the company started out as the Bristol Aeroplane Company of Great Britain in 1910. They designed and built many aircraft for both civilian and military use, including during both world wars.
Before WWII Bristol had worked with Frazer Nash, and post war they took over the company and started the Bristol Cars Company in the hopes of staying in business now that wartime demand for aircraft had dropped off a cliff. With over 70,000 employees, it was critical that Bristol Cars prove to be a success.
The first post-WWII Bristol production car would be the Bristol 400. Frazer Nash had worked closely with BMW before the war, going so far as to sell their own Frazer Nash BMW, and so it was decided to build on this prior knowledge.
The Bristol 400 would be powered by a modified version of the BMW 328 inline-six cylinder engine, and it would ride on a frame that was similar to the BMW 327. Into this platform a new body would be fitted, with a BMW-inspired twin kidney grille up front.
The engine is still fitted with the matching set of original carburetors, as well as the 2″ racing crankshaft, sports type magnesium oil sump, and the correct 3-into-1 cast exhaust manifold.
Bristol Cars would go on to become a beloved supplier of high-end automobiles for the wealthier classes in Britain. The company closed its doors in 2020, many believed forever, but the company has since been revived, and is now working on releasing a range of electric cars.
The engine used in the BMW 328 was a masterpiece of engineering. It was developed by Rudolf Schleicher and his team in Germany with hemispherical combustion chambers and inclined valves but without needing to redesign the block to accommodate double overhead cams.
The engine instead retains its single in-block cam which operates the valves by pushrods. Looking at the engine externally, it really does look like a DOHC design the first time you lay eyes on it, and it’s tripped up many a visitor to car shows over the years.
This is a 1949 Bristol 400 Sports Saloon, the car that was powered by a version of the engine you see in this article. Image courtesy of Bonhams.
This rare Bristol BS1 Mk3 competition engine is due to cross the auction block with Bonhams on the 8th of October and it’s described as being in complete condition but requiring a recommissioning before use.
If you’d like to read more about it or register to bid you can visit the listing here.
Images courtesy of Bonhams
Articles that Ben has written have been covered on CNN, Popular Mechanics, Smithsonian Magazine, Road & Track Magazine, the official Pinterest blog, the official eBay Motors blog, BuzzFeed, Autoweek Magazine, Wired Magazine, Autoblog, Gear Patrol, Jalopnik, The Verge, and many more.
Silodrome was founded by Ben back in 2010, in the years since the site has grown to become a world leader in the alternative and vintage motoring sector, with well over a million monthly readers from around the world and many hundreds of thousands of followers on social media.
