Vance
I didn't word-smith my post very well. When I mentioned one-piece forged, I
was referring to what APT sells or what BP Northwest sells as monolithic 21
4N stainless and having some disadvantages vis-a-vis mushrooming and stem
wear, since SS is softer than steel alloy. However, both of those valves
have reduced stem diameters just under the head for improved flow.
You are correct that these RPM valves (actually they are from SI Industries,
see http://www.sivalves.com/ocforeign_valvesrep_tri.html) are forged 21 4N
stainless with hardened (Stellite?) tips. Some portion of the stem
apparently is chrome plated. It seems to me that these valves are superior
to one-piece forged SS ones.
Here's the response I got directly from the "horses mouth"
THE TRIUMPH VALVES ARE SWIRL POLISHED, CHROME PLATED, 21-4N STAINLESS STEEL
MADE IN ONE PIECE FORGINGS. THESE ARE NOT AVAILABLE IN NITRIDED COATING. THE
INTAKE IS 1.450 HEAD, 5/16 STEMS AND 4.600 LONG. THE EXHAUST IS 1.260 HEAD,
5/16 STEM, AND 4.600 LONG. BOTH ARE HARD TIPPED.
And here's the best part if you go directly to SI:
THE COST OF THESE IS $11.95 EACH, AND WE HAVE THEM IN STOCK.
--
THANK YOU
PETER WIGBELS
GENERAL MANAGER
--
I like the idea of doing the 30-degree undercut, but I do plan on pocket
porting (the head sits on my workbench as I write).
Thanks
Jerry
----- Original Message -----
From: "Navarrette, Vance" <vance.navarrette@intel.com>
To: "Jerry C Shaw" <slowtoaccept@yahoo.com>; <6pack@autox.team.net>
Sent: Friday, December 03, 2004 10:51 AM
Subject: RE: Interesting source for SS valves
Jerry:
Read the copy carefully - They are claiming the stems are
chromed,
which eliminates the worries about wear on the stems. They are also
claiming
that the tips are hardened, which resolves the concerns about
mushrooming.
The copy gets a bit confusing at this point; The text says that
the heads are swirl polished, which helps flow a bit but the picture
shows
non-swirl polished valves.
If they are truly swirl polished, then they will flow better
than stock.
You can always chuck them up in the drill and stone them to add a 30
degree
back cut to help the flow even more.
The undercut heads (necked down stems) does help flow as well,
but increases
valve head temperature on the exhaust. I would suggest pocket porting as
an alternative
if you are truly worried about flow...
Just my $0.00002
Vance
------------------------------
Cogito Ergo Zoom
(I think, therefore I go fast)
TR6 Web page: http://home.comcast.net/~v.navarrette/
-----Original Message-----
From: owner-6pack@autox.team.net [mailto:owner-6pack@autox.team.net] On
Behalf Of Jerry C Shaw
Sent: Friday, December 03, 2004 6:21 AM
To: 6pack@autox.team.net
Subject: Interesting source for SS valves
Found this website for TR6 valves.
http://www.rpmrons.com/SIvalvesrep_tri.html
Advantages: Stellite tips, chrome steel stems, 21 4N SS heads
Disadvanage: Not undercut to improve flow
Some have said that one-piece forged 21 4N SS valves mushroom at tip,
and
absolutely require bronze valve guides because stems are not hardened
steel.
Anyone tried these?
|