Hi,
RazorBob asked about head mods... It needs to be stated that mrely
grinding material away in your cyl. head will not necessarily make the
head flow better. You need to remove the _correct_ material in the proper
amounts. That said, if you merely port patch and grind any "chunks" out of
the ports (trust me, you should see some of the casting swarf that I've
come across in a relatively small sample) you'll flow better.
The next step would be to either chuck the valves in a lathe and modify
ala Kastner _or_ get some stainless replacement valves from a source like
APT (www.aptfast.com) or others. This will net improved flow without
getting into nitty gritty flow details.
The stock valve heads transition to the stem over a fairly large distance.
I don't know the dynamics, but I'm pretty sure that if you flowed one of
these valves next to a fancy stainless jobbie, you'd see some improvement
from the stainless. Addd in to factors - the stainless vlave is lighter
(++) and the stainless valve is _forged_ (++++) and you have a win-win-win
situation. +++ Lighter is better to reduce chances of valve float and ++++
the stock valve head is welded to the stem. Get that puppy too hot and you
have real problems on your hand (although I've never seen a TR6 valve head
fail, I'l bet that they can, especially if you run high compression or
boost - especially boost.
So, port match, clean up the swarf and before you start cutting the head
(aka porting/polishing), look into new valves. The valves are not cheap
(over $30 each from APT), but if you shop around you can get them for
under $20 each from any place that specializes in custom valve
applications.
If anyone wants to do a side-by-side bench flow, let me know. I have all
the above (but no direct access to a flow-bench).
rml
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