Big Displacement DOHC Engines

Question: Other than Mercury Marine/Racing, why hasn't any other manufacture or builder, designed a large displacement (More than 7.0L) DOHC engine?


The 1928 Duesenberg Model J used a 7L straight-8 with 4 valves per cylinder. Supercharged, too.
$$$$$$$$$$$$$$$$$$$$$$$$$$$ and low sales numbers. But I do like the Boss 9 lineup.
There hasn't been a engine on the market to give a chance to prove itself. I know on a cost/hp an LS is tough to beat given the simplicity, reliability and robust aftermarket it has, but you would figure by now someone (Other than Mercury) would have prototyped something.

The Boss 9 isnt DOHC, it is a semi-hemi I believe.

Randy V

Staff member
Lifetime Supporter

Large enough displacement?


Interesting that the design of the engines I worked on back when I was just a lad in the late 60’s early 70’s is making an apparent come-back... I worked on Fairbanks-Morse and Waukesha 2 stroke diesels that were built in the 40’s that had dual crankshafts and no cylinder heads. Massive power at low RPM.