Thanks for the input. I will put "Tuning for Speed" on my want list.
Tom
ardunbill@webtv.net wrote:
>
> This discussion is persistent which shows both that people are
> interested in the subject, and it is not a settled matter.
>
> Some contributors to the discussion are time-served veteran racers who
> have learned the hard way what works for them.
>
> Less-experienced people may find great value in a study of the
> fundamentals, which are expressed most readably in the old classic
> (updated to the fairly recent 6th edition, which is in print) "Tuning
> for Speed" by the late P.E. Irving, one of the greatest engineers of the
> old (pre-1975) British motorcycle industry. Mr. Irving was best known
> as the designer of the immortal Vincent motorcycles which were both
> tremendously successful road bikes, and in racing form held speed
> records in many countries, as well as the World Motorcycle Speed Record
> in the mid-1950s.
>
> Whether air-cooled or water-cooled, car engine or motorcycle engine, the
> problem for the racing four-stroke engine is the same as it has been the
> whole of the 20th Century. Hence the value of the study of "Tuning for
> Speed" for the speed trials competitor.
>
> In a nutshell, Irving tells us that piston trouble (holes) arises from
> excessive internal temperature, which in turn arises from the
> relationship between the fuel qualities (whether gas, alcohol, or nitro
> blends) and the compression ratio. He assumes that mixture is correct
> for the fuel, and spark lead and all the other factors are as they
> should be. And there are many factors that bear on the subject.
>
> The crown of the piston is probably always the weakest part of the
> combustion chamber, and the part that fails first when there is
> "excessive internal temperature."
>
> It's probably fair to say the only difference between air-cooled and
> water-cooled racing four-stroke engines is that the latter run around a
> 200 degrees F. cylinder head temperature while the former easily run 400
> degrees and over. This has a lot to do with the said "internal
> temperature," the immediate practical effect being that air-cooled
> racing engines must use substantially lower compression ratios than
> otherwise-equivalent water-cooled units.
>
> A recent catalog of Classic Motorbooks lists the above book as item
> 107755D and you can access them at 800-826-6600.
>
> I've been riding and building motorcycles, road and racing jobs (many
> Vincents) for more than 40 years. But all with carburetors. So this
> Hilborn on my Maxton Ardun threw me, at first. But I believe I've got
> it figgered out now. We'll see. Regards to all, ArdunBill Hoddinott
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