andyfeaver
Joined: 15 Apr 2024 Posts: 14 Location: Cheshire, United Kingdom
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Posted: Mon Nov 11, 2024 9:22 am Post subject: 4 litre cylinder head design - contemporary observations |
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Hello all,
As well as a BDC member, I am also a member of the RREC and have been trawling through their archive looking for things to help with my understanding of the 20/25HP water pump.
While doing so, I have come across some very interest contemporary analysis and comment on the 4 litre cylinder head - which was being analysed by Rolls-Royce to understand what their competitor Bentley was doing with it.
It is clear from WO's autobiography that he did not like the 4 litre engine, I think there is more than a wiff of "not invented here" syndrome. True, when mated to the 8 litre chassis, the car was overly heavy - but the engine itself was actually rather good. Those who also are interested in post-war Bentleys will notice that the "F" head design (overhead inlet, side exhaust) of the 4 litre was used in the Rationalised Engine range (B series) which powered all Bentleys and Rolls-Royces from 1946 until the introduction of the L series V8 in 1959.
I would be interested to know if this has been discussed before?
AF |
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Stephen Blakey

Joined: 02 Feb 1995 Posts: 1337 Location: Derbyshire, United Kingdom
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Posted: Mon Dec 30, 2024 8:19 pm Post subject: |
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It has. You should be able to find some posts by the late Alan Smith who rather cornered the market in these engines a while back.
It's interesting that R-R had this test data from the 4L while BM was still a going concern.
As you will see from the cross section you kindly posted, there is no way of significantly increasing the compression ratio of this engine, and it is stuck at a lowly 5.5. BDC members, being inveterate tinkerers, evidently haven't found much here to get excited about. It was, however, Alan's dream to design his own cylinder head, which was to have had improved tuning potential.
How sad that the few remaining 4L cars are still in danger of being destroyed, so their chassis can be used in specials. |
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John Murch

Joined: 05 Jun 1976 Posts: 1567 Location: London, United Kingdom
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Stephen Blakey

Joined: 02 Feb 1995 Posts: 1337 Location: Derbyshire, United Kingdom
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Posted: Tue Dec 31, 2024 6:41 pm Post subject: |
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I agree with you about supercharging, as does Bert Degenaar evidently. It would be good to read about his project in the Review.
It's great that Alan's musings are still available on the interweb. |
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