We don't work on a lot of vehicles here these days, but took on a 1970 GS Stage 1 455 recent restoration for some "custom tuning". The owner dropped the car off, recent engine rebuild, 3.55 gears installed, and it still had the stock 13" converter in the transmission. The engine was mildly warmed over, about 9.5 compression, TA-212 cam, minor head work, stock intake, factory correct Q-jet (our contribution) and stock exhaust manifolds. Due to the camshaft upgrade and still using the stock converter, this combination just wasn't happy. After our best carb and distributor tuning efforts, and making some nice improvements to how well the car drove, we just felt that it was somewhat lacking in overall performance and needed some help. At this point we called Jim and talked about a converter upgrade. He had a custom 9.5" converter built for us and shipped here for installation. Ill be quite honest here, when I opened the box and saw this little converter I was a bit concerned that it would be able to effectively manage the power from the big Buicks 455 and the heavy weight of this vehicle. My experience with converters is quite extensive, and anytime weve went to these small converters they have rewarded us nicely with a LOT of stall speed, but in the same sentence have been horribly inefficient for normal driving, and almost always poorly coupled in the mid-range and some even very loose on the top end. Jim and I had discussed this problem and he assured me that the custom 9.5 converter would be fine in this application. The install went without a hitch, took us just over hour and a half, and other than having to open up the flywheel holes slightly and shim the converter (per directions supplied with it) a bit, fit was perfect. The moment came for the test drive and we immediately noticed that the engine rpms dropped slightly when the trans was placed in gear and it drove off the lift with little effort, or additional rpms more than it would have needed from the stock converter. Reverse is where you always see that a converter is too loose and/or you can get a good impression of how well it will be coupled at lower rpms. We did some extensive testing over the next half hour or so and came back to the shop quite pleased with the results. Ill say here that I am typically NOT impressed very easily, as the daily drivers we own here in the shop are high 10 second to low 11 second cars. Its also very important with these things to have a good combination, sort of like a recipe, when you set up a vehicle to make optimum power and provide decent performance on pump gas only. For this particular vehicle, we were completely unimpressed with the combination before the converter install. It was basically a turd just about everywhere, engine rpms dropped too much when the trans was placed in gear, sluggish off the line, wouldnt even squeak the tires when hit with full power, and just starting to show its colors a bit up near the shift point. After the converter upgrade, this is now a completely different vehicle. It drives better everyplace, plenty of torque multiplication in any gear to effectively move the weight, and it will now ROAST the tires on full throttle starts, or below about 15 mph on roll-outs. It will also get sideways on the 1-2 upshift if you stay in it, and we are getting a hard chirp on the 2-3 upshift, showing how well the converter is coupled at full throttle. Anyhow, my hat is off to Jim for doing the homework for us, and coming up with a custom torque converter to put the finishing touches on this nice restoration. Im sure the owner will be as pleased as we are with itCliff
I got similar results from the stall converter (and tranny) that Jim built for my car - 455 with a little more than mild cam, aftermarket intake, headers, and quadrajet. UticaGeoff
Steve, that's the very best part of the 9.5" converter, it was fine for "normal" driving. It is also very well couple above the stall speed, which is where we usually find the most fault with the smaller aftermarket street/strip converters. We've tested BOAT LOADS of converters over the years, and I was quite skeptical that a converter this small behind the big 455 in a 2 ton vehicle would be efficient enough in the "normal" driving range, but it is fine. I did quite a few 3rd gear runs at low throttle positions up some slight to steep grades to see if it felt "loose" or allowed the engine to flash up too high. It's actually perfect for this engine/drivetrain/vehicle combination. The moderate compression ratio 455 with the TA-212 cam really loves the additional torque multiplication from this converter. It was NOT happy at all with the stock converter, as it kept the engine rpm's too low until the vehicle reached highway speeds (3.55 gears). Even better full throttle standing start are LIGHT YEARS better with this converter, the car is a "rocket" compared to being a big "turd" with the stock converter.......IMHO......Cliff
This is some good info... and good timing. This is where I'm at right now. My build is similar except it is a 430 running a stock TH400 and converter. I have the motor dialed in pretty good now but the transmission feels loose. Its fine when driven like an old lady but is lacking at WOT. I'm sure the transmission could use a good performance build but I could probably benefit from one of these converters.
I LOVE my TSP 9.5" converter even with the 556hp/556tq motor Jim also built for me. I hate that loose converter feel and also need one that's tight enough not to create too much heat during the extended highway driving I do. I couldn't imagine one being better matched for my combo. Steve - call Larry and ask him about what he thinks after going from a SP to a normal th400
Great thread, I was being swayed to purchase locally. After a few PM's with Jim I went with TSP 9.5 . Glad I did, I haven't run it yet but with all the positive reviews, I'm confident in the piece. also custom built for my application. I shimmed 1/8" for the flexplate weight and a trans plate adapter.
I've had the same experience with my TSP 9.5 converter. Tight enough at low rpms for normal street driving, but give it some torque and it multiplies like crazy. Hats off to Jim for his magic!
