Guest Posted September 14, 2000 Share Posted September 14, 2000 ok, my 70 455 is in the machine shop, and i'm bout to get my tranny rebuilt. i was wondering what this stuff about a switch-pitch stall converter was. what are they and what is the benifit of them? my car will be a weekend street/strip car. but mostly street i imagine. i want to set up my drivetrain to be as efficient as possible and want to know what yall guys think as to what type of stall converter and rear ratio. thanks<BR>TexasRivi Link to comment Share on other sites More sharing options...
The Old Guy Posted September 14, 2000 Share Posted September 14, 2000 The switch pitch is a convertor used from 64 to 67 and had the capability to shift the vanes in the convertor to give a higher stall. They do help launch the heavier cars ,but if you want a really great street-strip combination ,put in a 3.3-3.9 rear gear and put in a 200-4R. This will give you the best of both worlds, a 2.76 first gear and a .30 overdrive Link to comment Share on other sites More sharing options...
Guest John Chapman Posted September 14, 2000 Share Posted September 14, 2000 Tex,<P>Try these posts for more detail on the SP transmissions.<BR> <A HREF="http://www.aaca.org/ubb/Forum2/HTML/000336.html" TARGET=_blank>http://www.aaca.org/ubb/Forum2/HTML/000336.html</A> <BR> <A HREF="http://www.aaca.org/ubb/Forum5/HTML/000313.html" TARGET=_blank>http://www.aaca.org/ubb/Forum5/HTML/000313.html</A> <P>Cheers,<BR>John<P>------------------<BR>John Chapman<BR>BCA 35894<BR>1965 Skylark Convertible (Some Assembly Required)<BR> jmchapman@aol.com Link to comment Share on other sites More sharing options...
Guest Posted September 15, 2000 Share Posted September 15, 2000 Switch pitch will work excellent in your set up.What I am did to my 70 Wildcat was install a rebuilt 1967 400 tranny I got from an electra. Cost to rebuild was the same.I got the s/p converter from Poston and installed 3.23 rear gears from a 66 Rivera.My motor has a 113 cam ,ta intake and a 72 800cfm rochester carb.Very pleased with performance and mileage.S/P converter will only work with the S/P tranny. Link to comment Share on other sites More sharing options...
Guest Posted September 15, 2000 Share Posted September 15, 2000 Well, i've already made plans to get my TH400 rebuilt, and i was just wondering what i can do to it to improve pickup-and-go over stock. Does this mean that a S-P converter will or wont work on my tranny/car? Once i get it all put back together and running well, i will choose a rear ratio to compliment the rest of my car. thanks for the info.<BR>TexasRivi Link to comment Share on other sites More sharing options...
NTX5467 Posted September 15, 2000 Share Posted September 15, 2000 As I recall, the basic architecture for the THM400 is the same, just the converter and front pump must match--switch pitch converter and switch pitch front pump, for example. The electrics to make the switch pitch items work can be wired extra and toggle switched instead of using the factory carb linkage switches--one for kickdown at WOT (normal THM400 item) and one to detect idle and WOT (times when the pitch switched to the higher ratio) as the vehicles came from the factory with. The wiring junction on the side of the case might need to be 2 wires instead of one wire as in the normal THM400.<P>The switch pitch item was neat. It let the converter be looser at idle (less creep) and when additional performance was needed (WOT) plus be tight for low performance/cruise situations. It was an easy upgrade for Pontiacs and other non-Buicks or non-Oldsmobiles with THM400s.<P>Enjoy! Link to comment Share on other sites More sharing options...
Guest Posted September 15, 2000 Share Posted September 15, 2000 There is an electrical connection on a 70 TH400 besides the Neutral saftey switch?<P>This is a 3 speed Trans. not designed for Switch Pitch, why would the Electronics for SP be there? For some reason I find this highly unlikely. Or am I completely misunderstanding the Reply. Link to comment Share on other sites More sharing options...
Guest Posted September 15, 2000 Share Posted September 15, 2000 To Russ:<P>I'm rebuilding a 455 for my 70 convertible with the 113A cam and was going to redo the tranny I got and go with a 3000 stall S/P. What kind of performance does your car do? Have you run it down the quarter mile? Or what have you beat on the street? I'm trying to put my car into the 12's so some snot-nosed kid with a Mustang or daddy's Corvette won't beat me. Thanks.<BR> Link to comment Share on other sites More sharing options...
The Old Guy Posted September 17, 2000 Share Posted September 17, 2000 I ran a switch pitch and it worked great! The only problem is ,if you want 12s you will need a gear and that means winding the engine on the road ,unless you put in the OD unit.When I switched to the 200-R4 the RPM drop on the highway was from 3300 at 70 to 2200 and the mileage was up 4MPG. My car is a72GS convert and with a mild engine and 3.31 gears it runs 13.0s Link to comment Share on other sites More sharing options...
Guest Posted September 17, 2000 Share Posted September 17, 2000 Dale W<BR>Regular TH400's had an electric kickdown switch. So they all had some kind of electrical connections. Link to comment Share on other sites More sharing options...
Guest Posted September 18, 2000 Share Posted September 18, 2000 I never ran this combo at track yet.I used to run a stock 90 GT which did 1440s. The Wildcat pulls harder and on street has won and lost to 5.0's & Camaros.None of these races were preset they just occurred.I am waiting till next year to see what she does as she is now under major body restoration.My plans are to use as a show car with an occasional strip run. Link to comment Share on other sites More sharing options...
Guest Posted September 18, 2000 Share Posted September 18, 2000 To The Old Guy:<P>What kind of mods were done to your engine to get the car into the 13.0's? I'm doing a full rebuild with lots of goodies including .030 bore, fully balanced bottom, reconditioned factory rods with TRW forged pistons, a Poston 113A cam, double roller chain, 1967 430 heads which were fully ported and have Stage1 valves and double valve spings and 3-angle job, also an Edelbrock Performer manifold, Poston 3" header/exhaust system, a switch/pitch T400 with the 3000 stall converter, and either a rebuilt qjet or a new Demon 850 street carb. I'm not sure on the rear. I have a 3.42 open right now and I know that won't do. I'd like to get a 3.23 up to 3.55 posi unit, but they're tough to come by up here in Ohio. If anyone has one they'd like to sell, let me know. Link to comment Share on other sites More sharing options...
Straycat Posted September 19, 2000 Share Posted September 19, 2000 <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by TexasRivi:<BR><B>...i was wondering what this stuff about a switch-pitch stall converter was.... TexasRivi</B><HR></BLOCKQUOTE><P>TexasRivi, <P>Are you running a big Riviera? Do you have AC? Are you going to stick with a mild build-up?<P>I was once told by a Kenne-Bell tech (about 20 years ago) that with a bone stock 455 engine rebuild on a heavy GS Riviera with 3.23 rearend gearing, that a switch pitch was a waste of money. Not enough camshaft, gearing, or traction (with street tires) to allow the switch-pitch to really work properly. The bone stock GS Riviera 455 makes all of its torque on the bottom end, so tire traction is a major problem to begin with.<P>The Kenne-Bell tech said to try this simple test. With your current engine/rearend gearing/tire combination just stand on the throttle from a standing start. If you tires go up in smoke, adding a switch-pitch will just make matters worse. If you bolt on a pair of slicks at the track, then the switch-pitch might not be a problem. It always comes down to tire traction with the switch-pitch.<P>The Kenne-Bell tech also assumed that I wasn't buying the switch-pitch for its added "passing" gears. He was correct on that. I just wanted to increase my 1/4 mile times on street tires. With that in mind, he stood by his recommendation of not using the switch-pitch for my (at that time) current combination of parts.<P>There are now many different combinations of stall speeds available for the switch-pitch converters from vendors such as Poston. This is actually a good thing, but you have to make sure you buy the proper switch-pitch torque converter for the right application.<P>As a side note, I?ve noticed that the fastest "stock appearing" :-) Buick GS?s of the GSCA club do not use a switch-pitch torque converter. They claim with a properly designed conventional torque converter, there is no need for a switch-pitch (when it comes to 1/4 mile racing). These guys and gals do run fast!<BR><p>[This message has been edited by Straycat (edited 09-18-2000).] Link to comment Share on other sites More sharing options...
Straycat Posted September 19, 2000 Share Posted September 19, 2000 <BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by The Old Guy:<BR><B>...put in a 3.3-3.9 rear gear and put in a 200-4R... </B><HR></BLOCKQUOTE><P>I've seen this combination recommended before. Looks good. I notice that a 3.42 rear gear was the max with the older AC equipped cars. Can I go beyond this without damaging the older AC compressors? <P> Link to comment Share on other sites More sharing options...
The Old Guy Posted September 19, 2000 Share Posted September 19, 2000 my GSis a 72convert, and it has a mild engine with a 3.31 gear. The engine is .030 with hypereutectic pistons ,an old SP1 cam, stage 1 heads ,a B4B intake,Q jet carb,KB headers with the 21/2 club exhaust with Flow masters, the old point ignition with a MSD-6A box,some bowl work on the heads and ports gasket matched. I use BFG drag radials(26X10) and a 200-4R .It ran 13.05-105 with the switch pitch and I know when I learn how to launch it with the 200-4R it will be quicker. I think I'll need a little more tire. The car weighs 3990 without my fat butt in the seat Link to comment Share on other sites More sharing options...
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