How easy it is to cause confusion with cam numbers?

[Pumaracing]

PeterBurgess said:

For playing 'what if' scenario number crunching games the numbers can be used from books, dangerous game extrapolating those figures as 'gospel' for the real world hands on tuning.

PeterBurgess said:

The forged rockers and pressed ones from early Minis are 1.28:1 as stated by both Piper and Kent in their cam catalogues.

LOL!!! A dangerous game except when you're frantically backpedalling and want to do it yourself eh? What was that I was saying about cognitive dissonance earlier?

Oh lordy lord that's funny. Quoting Piper and Kent as if they were the authority on anything to do with engines rather than the actual factory figures and real measurements taken by people as respected as Vizard and Hammill.

Anyway, I won't keep you. All that "real world tuning" you must be busy with today - from cam catalogues

[PeterBurgess]

Those 1.3:1 rockers we measured have been nagging away at me cos I could never see any offset but thought, what the hell, folk are very good at cheating standard spec engines. Browsing the net I came across an ad on Minispares website where they make replica cooper s rockers, these were also used on the MG Midgets but seldom still in place due to head swaps etc etc.
I attach a link to Minispares website and a pic of the page. So, life being what it is we seem to have 1.25:1 sintered Metro style, 1.28:1 pressed Mini rockers and 1.3:1 forged factory fit Midget and cooper S.

http://www.minispares.com/product/Classic/12G1221....








Peter

[PeterBurgess]

My mate Keith Calver has gone into overdrive playing with A series rockers and measuring them. He gets different ratios from our measurements but describes two styles of pressed rockers, small bore ones and large bore ones having totally different ratios, we now have four different ratios on A series engines!!!!!

Lifted from his webpage;

Identifying pressed steel rockers. Top shows round pad of the small-bore one - 1.23:1 actual ratio. Bottom shows oval pad of big bore version - 1.27:1 actual ratio.

From the top -1275 pressed steel (1.27:1), forged original ‘S’ (1.22:1), and latest sintered type (1.21:1). Actual ratio drops as cam lift rises, so ratios are even lower when used with performance cams. So whatever you do, change them sintered rockers!

link to webpage, rocker measuring stuff at bottom of page.

http://www.calverst.com/articles/CH-Rocker_gear-Ge...

Peter

[Pumaracing]

PeterBurgess said:

From the top -1275 pressed steel (1.27:1), forged original ‘S’ (1.22:1), and latest sintered type (1.21:1).

So at last, much BS later and we're finally back to what I said in the first place.

Pumaracing said:

It usually didn't even measure up that high unless you picked the best possible rockers out of a bucketful or used offset bushes. Some could be as low as 1.21 or 1.22.

[PeterBurgess]

You also said

'The actual stock rocker ratio of A series rockers is about 1.24.

Stan, the nominal factory quoted ratio of stock Mini rockers was 1.245 as per both Vizard's books and also here (quoted rounded to 1.25) in Hamill's book.'

You saying 1.21 ratio does that mean Mr Hamill and Mr Vizard are wrong?


Now you only quote you saying 1.21 which Keith measured for sintered late rockers. Make up your mind which of your ratios you are sticking to, and whether you are going for Keith Calvers lowest of 4 rocker types measured or for Mr Vizard and Mr Hamill's 1.24 you first stuck by, you are jumping around a little here Dave, what about the other three types of rocker?

Peter