[Fot] roller rockers and head flow

[U K MOTORSPORTS]

On our current race motor for the TR6 we bored the lifter holes for ford
lifters...Ted is correct...the lifter bores are not perpendicular to the
block face....What we did is used a CNC machine and wrote a program to do
the job...the blocks are between 1 and 2 thousands from one to another
using the locating tabs on the pan flange surface...aside from calculating
the degree of offset, each hole center was found, and lastly the lifter
directly in front of the cam drive needs to be moved forward about 25 thou
when using the 875 lifters...it is also important to do aprox. a .900 or so
cut initially in the very top of the bore to remove the webbing curve to
give a flat face to start the boring process and get a clean cut and not
destroy your bit...Chip


> [Original Message]
> From: Ted Schumacher <tedtsimx at bright.net>
> To: Richard Good <goodparts at verizon.net>
> Cc: <fot at autox.team.net>; <roadandtrack at bigpond.com>
> Date: 1/3/2008 3:58:27 PM
> Subject: Re: [Fot] roller rockers and head flow
>
> Richard Good wrote:
> > Rocker ratio has everything to do with valve velocity.  Lifter velocity 
> > times rocker ratio equals valve velocity.  Boring the block and 
> > installing .874" Ford lifters instead of .800" stock lifters allows the 
> > cam to be ground for 13.6% more lifter velocity.  Changing from stock 
> > 1.45:1 ratio to 1.65:1 ratio rockers increases the valve velocity 
> > 13.8%.  Do both and you get a 29% increase in valve velocity.
> >
> > Richard Good
> > Good Parts
> >
> > William G Rosenbach wrote:
> >
> >   
> >> Terry,
> >> Interesting stuff. But one question. You state:  
> >> Because these engines are so restricted by the valve & seat, then 
> >> the only way to improve them is by having very fast lifting cams and
> >> therebye
> >> having the vale open for the longest possible duration. The rocker
> >> arrangement has little to do with this.
> >> Doesn't the increased rocker ratio cause the valve to move faster as
well
> >> as further?
> >> Or is it just a case of to little a change to make a measurable
> >> difference.
> >> Thanks,
> >> Bill
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> >   
> Richard is correct. The caution is boring out the lifter bore.These are 
> on a 4.5 degree slant so you can't  run straight into the block and 
> overbore the lifter bores.  Ted
>
> -- 
> Ted Schumacher
> tedtsimx at bright.net
> http://www.tsimportedautomotive.com
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