From: hotrod@dixie.com (The Hotrod List)
Subject: Re: Big Cam, Lame Launch, Wrong gears
Date: Fri, 22 Jan 93 14:54:59 GMT
Organization: Dixie Communications Public Access.  The Mouth of the South.
To: hotrod@dixie.com
Reply-To: hotrod@dixie.com
Posted-Date: Friday, Jan 22 09:54:42
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 A 2-stage power valve may not be so bad if you have a low-RPM torque motor
(whether by design or because the rest of the power train keeps it there).
According to my O2 sensor the 1-stage power valve I have is markedly over-
enriching things at low RPM, medium-low vacuum (3-7"). At higher RPM and
zero vacuum it's about right. The main problem is getting  to the RPM where
the mixture is good.

 Since you seem to be set on staying with 3.08:1, there's only one other
way for you to move launch RPM up and that's a different torque converter.
There's the problem with slip at cruise - since you look to be set up to
cruise at about 2200-2500RPM and things start to happen at 2500, you're
kind of in a box.

 If you feel like pulling transmissions there's a fairly cheap experiment
you can try. Go junkyard fishing for the transmission out of a '65-'68
full-size Buick. These are called the Super Turbine 400 (ST-400). They 
have TH400 guts with the addition of a variable-pitch torque converter.
The converter has two pitches/stall speeds which are selected electrically
via an additional solenoid. One is lower than normal or near normal,
depending if you're used to motors that idle at 500RPM. The other is a
bit higher than normal, maybe in the 2500RPM stall speed range (I think).
Of course this stall speed is when it's stuck between a 430 or 425 Buick
engine and a 2.73:1 rear end, wrapped in >4000lb of blubber. An engine
with less than 445 lb-ft of torque in a lighter car might not push the
stall quite as high, but anyway.... Some of the Buick specialty places
like Poston have modified switch-pitch converters with other stall speed
combos. I think I recollect seeing ones like 1400/4000. 

 You can get the transmission from one of these Buicks (look for a Wildcat
or Electra) for the same price as any other used tranny - I've been given
a price of $300 for a complete 430 powertrain front to back at a local
yard, one which doesn't go out of its way to be cheap. They want $100 for
transmissions. If you do this, be sure to pull the throttle position
gizmo that's hooked to the intake manifold on the driver's side of the
engine. This gives automatic selection of stall speed based on pedal.
You can also add a toggle switch or rotary to give you manual control of
stall speed. If there is no funky looking gizmo (a linkage rod and a couple
of wires running from a 6" long, irregular body down to the tranny kickdown
connector - not to be confused with cruise control actuators) then you may 
be looking at a later or lighter model without the switch-pitch converter.
If you are looking at the bare transmission there will be a stamped
aluminum tag which says "ST400  Super Turbine". Any parts yard goombah
who's not a real Buick head is unlikely to know that this is a special
tranny. So don't clue them in.

 If you already have a TH400 and have invested in upgrade parts, Poston 
also sells kits to add the solenoid, 2-wire kickdown connector and switch-
pitch converter to any regular TH-400. This is good for Chevy guys who
would have to adapt the BOP-pattern Buick trans to Chevy otherwise.

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Posted by: emory!mlb.semi.harris.com!jws (James W. Swonger)
Newsgroups: alt.hotrod,wiz.hotrod