SU Spec cams?

[malcolm]

I have a 1969 4.2 litre series 2, 2+2. When I say I have it, I pick it up next weekend. Looking through the paperwork, I see that the cylinder head was overhauled by Rob Beere Racing in 2010. I contacted Rob Beere, and they confirmed that they did the work, and that they fitted "Upgraded SU spec cams"
Excuse my ignorance, but what does SU spec mean? And does it just provide a more efficient engine, or an increase in BHP?

Thanks for any help

[christopher storey]

Rob Beere are well thought of as tuners of XK engines. What the SU spec means is almost certainly that the cams are thought to be suitable for use with SUs rather than Webers, which are used on a conversion for which Beere supplies manifolds , etc. You might ask them what the spec is i.e. timing and lift . As to the effect of them, being a bit of a cynic I would say that they are unlikely to increase efficiency , probably will increase the top end power from about 4000 rpm onwards where you don't need it , and will leave a hole in the low to mid range torque curve right where you do need the torque . The latter was certainly the effect in the only engine we tried them on , and I think Heuer had the same experience, exacerbated in his case by a 6 branch exhaust system of significant diameter . My cynicism arises because throughout the entire 40 year life of the XK engine , Jaguar, who knew just a little about getting power from the engine , changed the cam timing hardly at all, the only radical change being the change to parabolic cams for quietness in about 1969 - and even that did not alter the fundamental timing, although at some stage both cams were retarded by, I think 4 degrees, for emission control purposes

[malcolm]

Thanks for the reply and info. I don't have much experience driving e types, so can't really compare. It does seem to have plenty of low down torque, but only comparison will tell if it's as much as other 4.2's. I think you're right in that overall, manufacturers know best.
I've dropped Rob Beere another email, so I'll see what they say.

[malcolm]

Spoke to Rob Beere about this cam now. Apparently it is a small performance increaser, specifically designed for those who retain SUs rather than go to Webers or similar. They said that if you increase cam duration, you lose idle and some torque, so this cam just increases lift rather than duration. He reckons idle and torque will remain the same, but BHP increase by typically 20bhp. Interesting guy to talk to.
Least I know now! And I can confirm that idle is steady as a rock at 700rpm

[utz]

20 HP for the RB Su spec cam is a big plus


RB.. Fast Road RBC4 0.415" 282

the question..

can someone tell me how a Weber-spec road cam with big valve could look like?

more duration because of the 6 throttles?

but more duration means bad idle, bad low torque, bad fuel consumption

or more lift...

i prefer at the moment

19-59 59-19 lift .404 .012 258?

for road use

who has experience with it?

let me know...

[malcolm]

Can't answer your question I'm afraid, but would point out that the extra 20BHP mainly came from the new cam, but they also fit bronze valve guides, cut and lapped valve seats, and generally finish the head to "concours standard" - so a few other little tweeks.