Folks,
As part of the on-going development of our MK1 PI & GT6 racers, the cyl
heads are next on the list for serious attention.
The 2.5 head has already had a lot of attention, but it is the HP limiting
part, so it needs more work if we are to extract more power (currently
200BHP at rear wheels). The GT6 head has 2500 sized valves and slight
port/chamber mods, but is far from radical. A more radical head is 90%
complete for this car, and is yet to be tested.
Six appeal (UK 2000-2500 register mag) published an article by Chris Witor
which showed some flow values for a standard Mk1 head, and with 2 different
modifications.
Assuming the tester used the "industry accepted" value of 10" water gauge
for the test, then
the general equation for estimating HP can be used. It is.............
Peak Engine HP= 0.43 x peak exhaust port flow in CFM (at 10" WG) x
no.cylinders
Using his figures, a standard head would flow 103HP (about right) and a
modified head with 31.25mm valves would flow 150hp, again, not a bad guess
based on my experiences.
I have a "friendly" operator of a flow bench ready to let a few triumph
racers test a selection of 6 cyl heads and mods at no charge. If anyone
can
provide any factual data on 6 cly head flows I'd be grateful.
Anybody want a pic of our racer can e-mail off-line
Terry O'Beirne
Australia
Mk1 PI racer, TR5, GT6 racer, etc etc
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