Has anyone actually put milder cams in their v12 - following the comments of Roger Bywater on his AJ6E website,
If so - what profile did you use, and where from?
Please, a link to Roger Bywater comment.
I have wondered whether a competent cam shop could regrind a set of OEM camshafts into the shorter duration profiles that Bywater developed for street use.
He talks about 20 degrees less duration, but the same lift, so it sounds as if that is all material to be removed
I wonder how much the torque curve changes
A very accurate, and telling passage: bolding mine.
One might reasonably conclude that the ideal cams for the smaller over-square cylinders of the V12 would have been of shorter duration than had been used for the XK. Many years ago we produced short period cams for the V12 which significantly improved acceleration but they were hard to sell because they did not give more top end power – which few people ever use, but which everyone seems to think they want.
yes - exactly
this thread isnt about making a 7000rpm racing car, but exploring the idea that a milder cam might make a better drivers car
I’d like to see some data about how much better the mid range torque is (and how much the top end suffers)
I am working on it. but I can tell you this. It is not possible to make less duration of the standard cam without decreasing the lift, the tip of the nose will be to sharp and you get a fragile cam. a 2-2.5mm radius is considered minimum. If you want to have like standard duration and more lift you need to increase the basediameter of the cam to make the lobe geometry better. I am doing this now to make a mild high lift torque cam for my next engine test together with my cnc ported heads.
But these cams have 4mm larger basediameter and 12.5mm lift, so you need to machine the cam housing to make room for the lobes. But when this work is done I can do most any profile in the future and have it fit in the heads. with larger basediameters you get more freedom for better profiles at a given lifterdiameter and such. But a -20 degree cam would probably need low lift even with this basediameter.
Best regard
Ole Mobeck
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Wow, 12.5mm lift. It’ll be interesting to see how that engine runs. I am of the opinion that the reason a basic SBC can develop so much more power than the Jaguar V12 all has to do with breathing. I believe some claim the ports are inherently restrictive, but the short lift of the valves doesn’t help.
Pushrod engines have a big advantage in that the rockers can be used to multiply the lift, usually like 1.7 or even 1.8 these days. So a Chevy LS engine can have 0.600" lift right out of the box. The only way to get that sort of lift with a flat tappet OHC is with either very long duration or very large base circle.
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Now, here it is. Almost ready, just need to skim/mill the heads
FB post about it
Best regard
Ole Mobeck
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They are finished and ready, complete matching setup
https://m.facebook.com/story.php?story_fbid=4723343531057356&id=495057580552660
Ole m
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VERY cool!
I hope @V12_Racer knows of these.
30 grams, off the valve stack, is significant, plus, the built-in hexagon for turning the cam is a very nifty touch.