8 hours ago, sethoflagos said:

Worth noting that from WWII to the early '50s the British public didn't have access to anything above 70 octane. Consequently production vehicles were built with low compression ratios. Hence the first family car I remember (1960-61ish) a hand cranked A30, would have had a compression ratio of about 7:1.

Indeed, in fact 7.5:1 according to Wiki, with the original 803cc version. : https://en.wikipedia.org/wiki/BMC_A-series_engine

By the time my Minor was built it was 948cc and a compression ratio of 8.3:1, eventually raised further to 8.8:1 by the time of the 1275cc version in the go-faster Minis, in the 1970s. It seems that, after the revamp to the A+ the same basic engine continued until 2000, by which time the compression ratio was 10.1:1. Power output was originally 28hp and in the final version was up to 76hp. Quite an evolution.

But I think one does tend to get this with IC engines. The 16SVT in the Class 40 diesel locomotive was rated at 2000hp, 2700 in the Class 50 (with intercooling) and in the much later Class 56, 3250hp. I've seen similar progressions with marine diesels. It seems because a new engine is such a big investment, the basic fixed components like the block are often generously designed to allow a lot of subsequent development.

Interestingly this a a little extra I did just learn from Wikipedia.

I had thought the industrial problems of both Austin and Morris did start untill the 1960s but apparantly it went back a lot further and even affected the war effor when morris were attempting to build spitfires.

In 1935, the Air Ministry approached Morris Motors Limited to ask how quickly their Cowley plant could be turned to aircraft production. In 1936, this informal request for major manufacturing facilities was replaced by a formal scheme, known as the shadow factory plan, to boost British aircraft production capacity under the leadership of Herbert Austin. He was given the task of building nine new factories, and to supplement the British car-manufacturing industry by either adding to overall capacity or increasing the potential for reorganisation to produce aircraft and their engines.^[34]

In 1938, construction began on the Castle Bromwich Aircraft Factory (CBAF), next to the aerodrome, and the installation of the most modern machine tools then available began two months after work started on the site.^[32] Although Morris Motors, under Lord Nuffield, who was an expert in mass motor-vehicle construction, managed and equipped the factory, it was funded by the government. By the beginning of 1939, the factory's original estimated cost of £2,000,000 had more than doubled,^[35] and even as the first Spitfires were being built in June 1940, the factory was still incomplete, and suffering from personnel problems. The Spitfire's stressed-skin construction required precision engineering skills and techniques that were beyond the capabilities of the local labour force, and some time was required to retrain them. Difficulties arose with management, who ignored Supermarine's tooling and drawings in favour of their own, and the workforce continually threatened strikes or "slow downs" until their demands for higher wages were met.^[36]

https://en.wikipedia.org/wiki/Supermarine_Spitfire

10 hours ago, TheVat said:

Heck, if the octane were much lower it would be halfway to being diesel.

Good call. It was basically straight kerosene.

Urkh! If so, the heavy end traces would foul the engine.

6 hours ago, studiot said:

Interestingly this a a little extra I did just learn from Wikipedia.

I had thought the industrial problems of both Austin and Morris did start untill the 1960s but apparantly it went back a lot further and even affected the war effor when morris were attempting to build spitfires.

https://en.wikipedia.org/wiki/Supermarine_Spitfire

I remember my grandad telling me that, to get around the scarcity of engineering skills needed for the war effort, everything was jigged where possible. This cut out a lot of the learning time needed to manufacture parts from the ground up, which was the norm then. He joined the RAF in 1936 as an airframe and engine apprentice.

Edited 10 hours ago10 hr by StringJunky

2 hours ago, TheVat said:

Urkh! If so, the heavy end traces would foul the engine.

Paraffinic heavy ends would resemble light luboil, so I’m not sure it would be that much of a problem. After all, diesel engines are built to a very similar design and don’t get gunged up. But there could be trouble with the carburettor, I’d have thought, with atomisation of the fuel.

1 hour ago, StringJunky said:

I remember my grandad telling me that, to get around the scarcity of engineering skills needed for the war effort, everything was jigged where possible. This cut out a lot of the learning time needed to manufacture parts from the ground up, which was the norm then. He joined the RAF in 1936 as an airframe and engine apprentice.

This is why the Mosquito was such an innovative aircraft, it did not require anywhere near so much highly developed skill or specialist machinery to make.
Indeed many furniture makers were redirected to manufacture large parts of the airframe.

6 hours ago, exchemist said:

Paraffinic heavy ends would resemble light luboil, so I’m not sure it would be that much of a problem. After all, diesel engines are built to a very similar design and don’t get gunged up. But there could be trouble with the carburettor, I’d have thought, with atomisation of the fuel.

Thanks, yes my vague reference to "foul the engine" - you have the specific problem pinpointed. I would guess it would need preheating and then much higher injection pressure to vaporize properly. Carb wouldn't do it.

Enjoying a thread where we seem to have a couple members like you who have some pro knowledge in this area. All I have, like @StringJunky , is a grandfather who really knew engines. But that was something.