[Healeys] Rocker Ratio Redux
PG
britishcars at shaw.ca
Wed Jan 6 11:40:54 MST 2010
I have 1.65 roller rockers on my car....stock valve cover is not a
problem....
However, you need to be careful with the geometry of the pushrods. With the
larger ratios, the angle and deflection of the pushrods can cause them to
rub against their respective holes in the head. I had my roller rockers
made in California by a firm ( www.rockerarms.com ) that had an old Healy
head around and they altered the rockers somewhat to allow for this. I also
went with longer moly pushrods (shorter tappets) to reduce the pushrod angle
and deflection.
I assume you are aware that the ratio affects your choice of camshaft and
the porting of your head etc. Simply changing the ratio while leaving
everything else stock may give you some unintended consequences.
While increasing the ratio won't change the overlap of the cams, it will
change the scavenging and ramming affect due to the increase in overall
valve opening volume.....you will likely loose torque and smoothness at the
bottom end with some efficiency gained at higher rpm....I've never just
simply changed the ratio, so I don't know the extent of the impact. Also,
with increasing the ratio, you may require stronger valve springs to avoid
bounce.
When I had my cam ground by Dema Elgin, I supplied him with my rocker ratio
as well as volumetric flow (at different valve opeings)of my ported head (as
determined by a flow-bench)...he then came back with the recommended Cam and
spring strength.
Paul
-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at autox.team.net]
On Behalf Of Walt Peterson
Sent: Wednesday, January 06, 2010 8:57 AM
To: Bob Spidell
Cc: healeys at autox.team.net
Subject: Re: [Healeys] Rocker Ratio Redux
Yep: Jim Hockert says 1:45. I'm looking at roller rockers 1:65 but am afraid
the set-up may need a tall valve cover even without a cam. Anyone?
Walt
--- On Tue, 1/5/10, Bob Spidell <bspidell at comcast.net> wrote:
From: Bob Spidell <bspidell at comcast.net>
Subject: Re: [Healeys] Rocker Ratio
To: "Walt Peterson" <walt2727 at yahoo.com>
Cc: Healeys at autox.team.net
Date: Tuesday, January 5, 2010, 11:02 PM
Nominal 1:1.5, though in reality it's a bit less I've been told.
bs
Walt Peterson wrote:
> rocker arm ratio for valve train, 3000: anybody know?
> Thanks,
> Walt
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Bob Spidell San Jose, CA bspidell at comcast.net
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