Hi Bob,
You may want to go to Crower's website if you still have your part
number
to find out what your cams actual lift is. Who knows what ratio they used to
arrive at .432". My cam has a lift of .286". When I did the math for a 1.5
rocker, I felt I was going to have to relieve the block under the exhaust
valve. (mainly from recommendations of this list and my machinist) So I
figured while I'm grinding I might as well grind for a 1.55. I talked at
length with Gary @ Rockerarm Specialists (nice guy) he said that with a 1.6
ratio you'll also need to open up the pushrod passages on your head. I
believe Dennis Welch's 1.6 is the same. IMHO I'd wait to rebuild the whole
engine to put a higher ratio roller rocker on. Without balancing the intake
with the exhaust(i.e. porting, headers, etc.) I don't think you'll see it's
full potential.
Best Regards,
Greg
P.S. Gary can mix the ratios when he builds the rockers.
> -----Original Message-----
>
> Listers,
>
>
> I'm planning an eventual rebuild for my BJ8 engine that will incorporate
> a few performance mods (mild porting, carb work, etc.). I'm considering
> doing some of the mods prior to pulling the engine, to see what kind of
> effect individual mods have.
>
> Anyway, I'm thinking about installing a high(er) ratio/lift
> rocker set from
> Rocker Arm Specialists. I see they come in 1.5, 1.55 and 1.6 ratios.
> Does anybody know if--for sure--which of these will "drop in" to a
> stock (no head or block skimming) 2912cc engine? I know you should
> dry build the engine to check clearances when you do this, but if anybody
> has dropped-in a, say, 1.5 or 1.55 rocker set with no ill effects
> would you
> let me know? My cam has an advertised lift of .432" (250deg duration),
> as opposed to the nominal lift of .368" (per the book, anybody know if
> this is "advertised?") I assume both are total lift, after
> multiplication by
> the rocker ... can anybody confirm? Looks like my cam grind has higher
> lift and shorter duration than stock (it was the mildest of 5
> available grinds
> from Crower Cams). It's a good cam, very stable idle and good low-end
> torque, but seems to tap out over 4,000 rpm.
>
> Maybe with the higher-lift cam I should use the 1.5 rocker? The stock
> rocker is a nominal 1.5, but I've heard they are all over the place and
> usually closer to 1.45 ... can anybody verify/dispute?
>
> Another note: in checking the Bentley manual, I note the valve rocker
> clearance for "Competition (Mk. II and III)" is .015", not the .012"
> listed on the rocker cover. Anybody know what "Competition" means?
> (BTW, the "Mk. II and III" are italicized in the manual)
>
> Ah, heck with it, anybody know what the best lift/duration cam and
> rockers are for a really torquey, quick, street machine?
>
>
> bs
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