[Fot] roller rockers and head flow

[Bill Babcock]

Years ago  a sharp machinist in Long Beach, CA did what he called a spherical
seat on the intake of my Matchless G80CS desert sled (single cylinder 500cc
motorcycle) Gave it a noticeable power boost with no apparent change in the
power band. I always figure an improvement you can feel with the seat of your
pants is at least 10%. The "spherical seat" was just a curved seat--no
angles--that was lapped by hand to seat the valve.


-----Original Message-----
From: fot-bounces+billb=bnj.com at autox.team.net on behalf of Jack W. Drews
Sent: Wed 1/2/2008 8:59 AM
To: Terry and Cindy; fot at autox.team.net
Subject: Re: [Fot] roller rockers and head flow

Terry, thanks for sharing this with us. I found the same thing with
my flow bench work on both Spitfires and TR6's.

Thanks for telling us about the straight port experiment - you saved
me all the work of trying this next.

One thing that I found interesting is the flow I measure on both 4
and 6 bangers with the valve totally removed did not increase as much
as I expected, and like you, could only conclude that the diameter of
the seat was pretty limiting. I have found that the 3-angle valve
seats act as advertised and are the biggest single improvement that
one can make.

At 11:17 PM 1/1/2008, Terry and Cindy wrote:
>I have yet to trial any roller rockers but it is planned for the in-progress
>rebuild of our race GT6 engine. I can however offer some real-world comments
>on head flow and related matters that might clear up some mis-conceptions in
>this thread....................................
>...............................I'd be happy to swap real results
>with anyone else who might have the same.
>I'd really like to hear from folk with cam data and anyone else who has
>experimented with larger valves and lifters.
>
>Terry O'Beirne
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