What does torque converter do and what do performance ones do. I have a th400 and want to know what to put in it. It still has to be streetable since it is my daily driver but not exactly soft riding.
Here you go, in a nutshell: http://en.wikipedia.org/wiki/Torque_converter A "performance" converter usually has two features...higher-than-stock stall speed, and improvements for higher horsepower/torque durability. Before you choose a converter for your application, you should let us know as much detail as possible about your car's combination and what you want from it. The aftermarket will also help you choose the right converter based on the same info. Devon
Heres the deal, I have a 1974 455 4bl conected to a th400 that will be going into a 1965 buick special 4rd. I would like it to be a fairly quick car that can hold its own with all but the best imports and muscle. Beat the integra, not to concerned about the supra though :3gears: . Also the 455 will be getting 74 or earlier heads and intake to get rid of some EGR and get the compression closer to 10.1. Also I am keeping the stock rear end and axel for time being, don't know if that play into it. What I am concerned about is if I get a 4000 stall speed converter will it not engage until 4000 and will I have to rev it up to 4000 to even go .
A 4000 stall converter will move the car well before 4000 RPM. What you want for the street, is a converter that is tight, but will stall higher when you romp on it. A high stall converter will not be fun driving on the street. It sounds to me like you have a basic stock 455 with maybe 9:1 compression. Don't go any higher than 2000 stall. The converter should be matched to the cam. With a cam that has a power range of 2500-6000, a 3000 stall converter would be a good choice. It will get the engine up into it's power range as the car leaves the line. You don't need that. The higher stall converter will get lousy gas mileage, create excess heat, and will cost you performance on the street. Bigger is not always better. try reading this thread. http://www.v8buick.com/showthread.php?t=55823&highlight=torque+converter
Depends on what you do for a cam. The Straightline 226/238 is a good street cam. With it you would want a converter in the 2000-2500 stall range. Changing to 71 or earlier heads will get rid of the emissions stuff, but won't gain you much compression. Compression in a Buick motor is mostly determined by the piston.
I wouldn't say "hard," but it does involve taking the motor completely apart and knowing what you are doing putting it back together. You could put stock bore high compression 70 pistons in the motor, but generally changing pistons is done only when a motor is worn and needs to have the cylinders bored for larger pistons. You would have to have a machine shop put the new pistons on the rods, at minimum. Yes, compression=horsepower, but it is only one of many things that make power. Many folks are making lots of power with low compression motors. For what is involved in increasing compression in a Buick engine, there is no reason to do it if the only reason is just to increase compression. If you need to bore the engine anyway based on wear, sure, buy the appropriate pistons and raise compression. But to take a motor apart JUST to raise compression is not worth the effort, in my book. Plenty of folks are running 12s, 11s, maybe even 10s with low compression motors. Just need to pick a cam that will work with low compression.
My next question What cam is that. Can you guys tell me the low comp setup, of course on the lower side of the budget. I was hoping to make 400 HP, the 70s kind.
There is a converter for every application you have to think hard before you choose what you want your end result to be. Also think of the converter as being an invisible clutch pedal. I was told the stock stall speed of my 1969 GS 350 was 1400 to 1800 RPM. Other things come in to play big time. A liter car or with lower gears needs less effort to move so it will move at a lower stall speed then a heavy car with high gears. Motors that develop a lot of torque at a low rpm will move a car easier (Buick). Again think like you had a stick! As you start to let out the clutch the car will move even though it is not totally engaged. The converter acts the same way this is why your car does not stall when you put it in gear. Kind of like just letting the clutch out a little with a stick. Your max stall speed is like when the clutch pedal has been let out all the way. In my case I have a stock car but it has 3.42 gears in the rear making it easy for the car to move. I also have a shift kit that used to drive my wife nuts with normal driving. I opted for a 2400 RPM stall converter. Let me tell you in my car it does not feel loose or sound like it never shifts floating from gear to gear like you get from a higher stall in normal driving conditions. What I found in my case was my car at idle (550 rpm in gear) wanted to drive away if you werent standing on the brakes That has been corrected. You still feel it when you put it in gear but the PULL is gone. This caused another instant improvement, my idle went up a little in gear causing my in idle oil pressure to increase. The other biggie is the first to second shift. You still hear the tranny snap into second but the bang in the drive train is gone (Happy Wife). This converter change is very subtle. If you had never been in the car before you would think its how it should be. I can feel a big difference after having the other way for so long. Performance factors? If I get into just cracking the secondarys it still lets out a nice chirp to the tires like it did before because everything is as it was above 2400 rpm. Stand on it from a dead stop and it definitely generates more power! That was easy to measure in the length of burn out the car did before and after! When I spoke to the (Very Nice and Very informative) people at Coan Converters they recommended a 2800 Stall converter with my setup. I hope some of this can help, I got what I was looking for in a converter! Mark
