I need a new torque converter, and was hoping for the best recommendation from those of you who know a lot about them (Jim Weise, Greg Friend, Larry70GS - are you there?). My motor is fresh, with about 1000 miles on it. We used the good Clevite bearings and the machinist is familiar with the correct tolerances for Buicks. Oiling modifications and balancing were also done. Here is the combo on a full weight, highly optioned 1972 GS with the BB TH400: 72 Stage 1 block, bored .030 over with '70 model 10.5:1 Seal Power pistons (the original 2362p's), with plasma moly rings 72 Stage 1 heads (I think actual compression is estimated around 9.5 or 9.6 now) GSCA "Popular Mechanics" fast ramp cam - 232/244 @ .050, 116 lobe centers (I'm hoping this wasn't a mistake!!) Edelbrock Performer intake and 800 cfm Quadrajet Mickey Thompson repro headers and 3" Headman X pipe system Original 10 bolt 342 posi Rear tires are 25.5 inches tall I would like to know what brand, size, and stall speed that would work the best on a weekend cruiser. I'm hoping to wake it up from a stop (it currently has the original GREEN converter in it!!), and will only use it occasionally for stop light racing. I am not worried about gas milage, but will have to drive it on the highway quite a bit since I live in the DFW metroplex (nothing fun is ever close!!). I was also wondering if anyone could guess the approximate rear wheel horsepower, and what a new converter will/won't do to the HP. Any help from those who know would be greatly appreciated. Thanks!! :TU:
If you are running 25.5" tires, your rear ratio will be more like 3.55. This means, at 60 MPH, you'll be turning 2800 RPM or so. The most important thing is you want the converter above stall speed when you are on the highway. With this in mind, you could easily use a 2500 stall speed. If the car is a weekend cruiser, and you don't plan on taking it to the track very often, or never, I would stay with the stock converter(about 1600 stall). You will have less problems hooking up, and you will still be able to easily smoke the tires if you want to show off. A high stall converter will give you traction problems on the street(unless you plan on running stickies all the time). It might be fun at first, then it can be frustrating. Of course the ultimate transmission for a street/strip car is the switch pitch(IMHO) That's what I am running, and it's hard to beat TSP's 12" switch pitch converter(3200/1800)
Thanks Larry. I do not want to change to a switch pitch tranny since the car has all the original #'s matching Stage 1 goodies. I would like to leave it as original looking as possible, but increase the performance as much as possible at the same time. I just need someone who knows converters to give me an idea of which one to use with my current application and drive habits. Does anybody else have an opinion?
I got mine from Edge Racing Converters in California. He has almost 100 different combinations of converter based on your car's engine/suspension/drivetrain specs. You can find them at http://www.edgeracingconverters.com/. A converter from them will run you about $475 or so, delivered. But well worth it IMHO. I got a Street Edge, and their converter in my car knocked almost .3 off my quarte mile time.
Thanks for the info, Phil. Can someone explain to me what advantages/disadvantages a smaller diameter converter poses? Is there any reason for a street driven car like mine to go with a smaller one, vs. the standard size with more stall speed? I appreciate the help.
Changing the diameter of the torque converter used is the easiest, least expensive way of increasing stall speed. All else being equal, for every 1" decrease in converter diameter, expect a 500 RPM increase in stall speed.
Changing to a switch-pitch type tranny will not change the appearance of your vehicle at all. In fact, you can even convert your current TH-400 to a switch-pitch if you wanted to. Switch-Pitch trannies are very cool. Think about it. :TU:
James, Adam makes a good point. You can have your BB trans converted to a switch pitch, and no one will know but you. The differences are internal(front pump, input shaft, and associated electronics). And, they are completely reversible. If the car is street driven with occasional blasts down the track, it's hard to beat the versatility of a switchpitch. Something to think about.
Thanks for the suggestion, Adam. Has anyone here done this? Are the parts hard to find and expensive? I don't think I'll race it enough to justify converting over to a switch pitch. I just want a GOOD converter that could be used for both weekend cruising and some occasional fun/performance. What does a stall converter due to chassis dyno HP #'s? Thanks to all for the suggestions. :grin:
James, Carl Rychlik(on the V8BB) runs the GSCA PM cam in his concourse 70 Stage 1. He has told me that he is running the stock Stage1 torque converter. I have driven his car, and it is plenty responsive. The stock converter has to be no more than 1600-1800 Stall at most. I would imagine a too loose converter would hurt HP on a chassis dyno. A torque converter multiplies engine torque when it is turning below stall speed. Once it reaches coupling speed it transmits power 1:1 (neglecting slippage which is present in all non-lockup converters). Shoot Carl a pm, he's a great guy, and always willing to lend some friendly advice.
James, I got your PM,and as Larry mentioned I do have the original Stage 1 torque converter and the Popular Mechanics cam. When I first was building my car,I was very concerned about the drivability of my car. Well after getting my car together,the results really surprised me. I really like the way my car runs. I thought that the cam would want more rpms off the line,but the stock Stage 1 converter seems well suited to the combination. The first time I let Larry drive my car he himself was very impressed with how my car ran. I think you'll like the way your car will run too, James. Good Luck!
Thanks for the replies, Larry and Carl. My car is already running, with about 1000 "easy" miles since the rebuild. It pulls pretty hard, but seems to stumble off the line. My thinking is it could be due to three or four things: 1. Timing - I am currently running about 14 degrees initial, and 32 degrees total. What have you found to be the best settings on your car with that cam? 2. Carburetor - Currently running a 1972 800 cfm quadrajet. This is more than likely the most obvious culprit. I am contemplating sending it to John Osborne, or switching to an aftermarket performance carb. I have rebuilt it with 76 primary jets, and the 43b metering rods. What are you running? 3. Cam - After being "sold" on the GSCA P.M. cam, I have heard some bad things about the performance. I am relieved to know you are happy with it in your car, but still wonder if it could be the cause. 4. Converter - I am pretty sure this converter is the original one my car came with (90K miles). It is a light green in color and looks like it is original. I bought the car back in 1982, had the BB 400 rebuilt then, and re-used whatever converter that was in the car (trans only has about 5-6K miles since rebuild in 1982). Anyway, the Lone Star Performance Buick Chapter of the GSCA is having "Dyno Day" this Saturday, with free dyno pulls for all club members. I think I am going to take my car and see what happens. I may try to fine tune the timing, and switch carbs if I can locate one that runs well on someone else's car just to see what happens to the HP. It will be my first time to use a dyno, so I am excited, but not very optimistic right now. That is why I was asking what a converter could do to dyno HP #'s. In other words, what happens when a converter is going bad? The trans doesn't slip at all, and the car will rip a second gear scratch every time with only cracking the throttle. Can a bad converter rob RPM's or HP at low speeds? Sorry for the long post, but wanted to let you know what I've been thinking. Any ideas? Thanks! :TU:
You're welcome,James.Just to let you know how my car is set up,I run the stock intake manifold and also have stock ported exhaust manifolds(Gessler's). I run the stock 730 cfm Stage 1 carb(#'s matching 1970 carb).For ignition,I have a Pertronix which works perfectly. The cam is installed 'straight up' and is not advanced. I run a total of 34 degrees total timing and the plugs I use are R43TS's. Anything else you want to know about how I have my car set up,please ask.
James, I believe you may be too rich on the primary side of the carb. I am running an 800 CFM carb (7042240), that has been prepped by John Osborne. It has 76 jets and 46B rods, with BG secondary rods(.0397 tips). Running leaner will make the throttle more responsive, especially off idle. You are 3 sizes smaller on the primary rods.
