It's 1PM but....
countersteer is right, Yamaha introduced a 5 valve head on the FZ 750 4 cylinder back in 1990's the Genesis head...it was extremely fast, outstanding power with a very flat torque... good memory countersteer...I used to live for engine design and remember a lot...some say 4 valves is the limit matching power output and balancing manufacturing costs ... but it must be effective as Yamaha still produces a 5 valve head on the 1000cc YZFR1 today ... so it must be worth the extra complexity, especially considering they have done it on a production engine over almost 10 years ....the easiest thing is to just increase displacement ... Yamaha must know if it's worth going past 4 valves ... several of their 4 valve F1 engines were regarded as the best of the field for a year or 3 ... just struck in unproductive chassis ... countersteer... don't remember a valve Yamaha in production though I do remember they were the first to introduce a 4 valve head on a 500cc twin way, way back in the 70's ... SZ it would be interesting to see any Suzuki research on contrasts of 4,5,6,7 valve heads ... but the SAE releases so many papers might be hard to find ... even an abstract ... they charge money for those papers too, much more than they should, after all they are mean't to spread knowledge and at 15USD+ it dampens curiosity ... I have some cut away pictures of the Yamaha somewhere and I know Honda used a very trick oval piston 8 valve in a racing engine. I have a cut away somewhere ... mx_tifosi Ferrari does say 4 valves is the limit of practicality but the Japanese have other ideas ... we will have to do some more research ... I have a pile of papers and scattered references in computer files ... sure I have a picture of Honda's 8 valve... someone probably remembers it ... it was a V twin with 2, yes 2 conrods a cylinder. a twin, and was mean't to head off the Japanese 2 strokes and preserve the Honour of Honda and the 4 stroke ... I'll look for theses items the next few days ... there's a lot to say even for the 2 valve head ... different configurations accent torque against power ... my brother had a 4 valve 850cc with 2 carburettors, 2 intake ports, 2 exhaust ports and a 2 into one exhaust header, the Dr Big, on-off road motorcycle ... the b
d sold it without even asking me if I wanted it ... sold it cheap, silly man ... don't know what's the matter with him, a very odd duck, doesn't always like to spread the tach wealth among all his motorhead brothers ... human nature is very strange ... since people are interested in this and probaby have a lot of insight lets keep up the reseach ... if F1 won't open up, we can and who knows if F1 will open up the rules a bit, just limit the outrageously expensive, toxic materials ... I'd like a formula libre restricted only by a fuel capacity limit ...it's almost 2 PM and time foe milk and cookies
EDIT - Mx_tifosa. is of course right in spades, good memory, Ferrari was the only car manufacturer to go with a 5 valve production car, very progressive and innovative. Poor me
almost 5 minutes to fight my way back into signin/edit mode. so tired of this, happens over and over, if I ever find another forum, that will be 50% 0f the reason ... 2:15 PM and the cookies are getting stale ( sigh)