The seat pressure needed is really determined by the ramp angles and lift
per degree of the camshaft. I have always found that the least amount of
pressure I could use resulted in a longer life to the cam followers and the
camshaft. Use alloy collars as they will reduce the amount of pressure
needed to keep the valves from floating. Anything you can remove from the
valve side is a BIG help. In the beginning (before I made the alloy collars)
I used a sharp edged grinding wheel to cut big wedges out of the steel
colars as I found you did not need the entire circumfrance of the collar to
hold the springs . In this way I ended up with a collar that looked like a
wide cross. REALLY CHEAP, EASY TO DO AND QUITE EFFECTIVE. In my pursuit of
lighter valve train I also cut the stem of the valves to a much smaller
diameter in alternate sections of the valve. This was a lot lighter but
acted like a pump to pull oil down into the combustion chamber. DARN. I
suggest you listen to the cam grinder for a recommendation.
----- Original Message -----
From: <Gt6steve@aol.com>
To: <FOT@autox.team.net>
Cc: <owner-vintage-race@autox.team.net>
Sent: Friday, December 31, 1999 12:53 PM
Subject: GT6/TR6 valve springs
> Happy Holidays guys, the transition seems to be going smoothly across the
> globe at this point...
>
> I'm still working on valve springs and pondering seat pressures, valve
float
> etc.. I'm assembling my brand new Isky "super comps" and shimming them to
a
> 1.350 spring height to get 90 lb. of seat pressure. I'm using stock steel
> keepers, tubular pushrods and "Yellow book" valves with a .468 valve lift.
> The yellow book and the TR6 book both tell me to go for 65 lb. seat
pressure
> but my machinist has fits and insists I need the 90 lb. to forestall valve
> float. Is there a reasonable calculation I can do for all this? Is there
a
> sound rule of thumb? The Isky catalog has seat pressure at 115 lb. for a
> spitfire which has shorter valves so the 90 sounds about right in that
> respect. Any enlightenment will be welcomed. GT6Steve@AOL.com
>
> BTW, the 1.65 rockers are going back on the shelf for now, Thanx for the
good
> advice from all. Steve
>
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