Thread: Straight Eight

From around 1930 to around 1950, a straight eight was seen in some circles as the apex of motoring, despite the drawbacks that were obvious to serious motor designers even before the first world war.

The advantages of more cylinders were obvious, but for most designers, six in line was the practical limit, and beyond that a vee engine became more attractive. The eight in line tends to be too long except in very large vehicles, the crankshaft too flexible, and getting even mixture to all cylinders or even cooling for that matter gets difficult. In practice, most of the ones actually mass produced, such as these Packard engines, were side valve engines, with poor combustion chamber shape, and low efficiency.

But they were cheap to build, especially if the company also built a six with a similar design, and the size and sound were impressive, as was the long bonnet they mandated!

Originally Posted by JDNSW

From around 1930 to around 1950, a straight eight was seen in circles as the apex of motoring, despite the drawbacks that were obvious to serious motor designers even before the first world war.

The advantages of more cylinders were obvious, but for most designers, six in line was the practical limit, and beyond that a vee engine became more attractive. The eight in line tends to be too long except in very large vehicles, the crankshaft too flexible, and getting even mixture to all cylinders or even cooling for that matter gets difficult. In practice, most of the ones actually mass produced, such as these Packard engines, were side valve engines, with poor combustion chamber shape, and low efficiency.

But they were cheap to build, especially if the company also built a six with a similar design, and the size and sound were impressive, as was the long bonnet they mandated!

You just summed it up. Packard addressed the poor combustion chamber design as best they could by tilting the valves toward the pistons , its as good as can be with a side valve setup, but of course compression ratio can never be higher than about 8:1 . I put the dual IDF Webbers on so that each cylinder has the opportunity to get even mixtures (and they were cheap) and there is a water distribution tube , like in later Chrysler side valves, looks like a long sword , pushed in behind the water pump - directs water onto the exhaust valve seats .

Back in the mid-Sixties, Dad had a ‘38 Buick with a straight 8. That engine was smooth when idling.

Originally Posted by p38arover

Back in the mid-Sixties, Dad had a ‘38 Buick with a straight 8. That engine was smooth when idling.

I think that was the engine used in the original Flxable Clippers.

Originally Posted by V8Ian

I think that was the engine used in the original Flxable Clippers.

Like the Pioneer Ansair Clippers? I’ve always liked the look of them.

Flxible Clipper - Ansair (1954) - Driver Classics

The Clipper’s fuel efficient light weight all metal construction, featured a rear mounted in-line Buick Fireball 320ci, ‘straight 8’ petrol engine.

But then there’s this:

With US trade restrictions firmly in place, sourcing of non-US components to use in local Clipper production proved difficult and resulted in a variety of UK and locally sourced components being used in Ansair built Flxible Clippers.

The first fifty-one Ansair Flxible Clippers used Leyland AU450 diesel engines with a 4 speed Spicer constant mesh direct drive transmission. The Leyland AU450 diesel was an upgraded civilian derivative of the Leyland 7.0 litre Matilda tank engine. This was followed by twenty Cummins JBS600 diesel engines and finally sixty air-cooled Deutz F6L614 and F6L714 diesels. None of these engines were particularly suited to Pioneer’s requirements with the Leyland engines being reasonable performers but without the engine life required, the Cummins engines good performers but also found wanting in durability, while the Deutz engines performed well but had head issues.

Detroit 6V53 and Perkins were popular conversions, the former officially approved by Ansair who provided conversion kit IIRC.

The observant amongst you will notice the Detriot Diesel badge on the front panel.

Flxible Clipper - Ansair (1954) - Driver Classics

Originally Posted by V8Ian

The observant amongst you will notice the Detriot Diesel badge on the front panel.

Flxible Clipper - Ansair (1954) - Driver Classics

Were they two stroke diesels ??