goofing around with the switch pitch, keeping on high stall with my 2-speed, when shifting into high gear the tach reads 4000 rpms. then on the next run I turned the converter off to low stall, the tach went down to 3300 after the shift. pulls better keeping it in high stall. but in low stall it got rubber between shifts.
One of the tricks guys do, and has been talked about on the board quite a bit, is switching the converter to low stall mid run. With only the 2 speed, you have a little more time to make the switch before you grab 2nd. Some guys use timers and others just keep their finger on the switch. They get a good launch in high stall and through the 60ft lights then hit the switch to low stall. It works better at different points in the run depending on your setup. Someone was building the timer boxes. I know Larry uses one in his 70.
That's what I do with my 66gs hardtop with a sp400. I have a hidden switch on the console. I leave the line in high stall and right before I shift into second I switch to low stall. And she runs very consistent that way. I pretty much do the same when driving around town also. Just put it in high stall at a stop light and low stall as soon as soon as your moving.
I usually launch in high stall, and then once the RPM's are up (~4000) I switch to low stall before I shift into 2nd.
I've never tried it,but wouldn't it be better to take off in high stahl and at a certain mph or rpm switch to low stahl and back to high stahl when shifting into second to keep the rpms up from the shift drop,then back to low stahl when the rpms or mph are caught up again in the power band?(for a ST300 2 speed,kind of making it a 4 speed)o No: Derek
That's just what I do, you have it right that keeps the rpms up between the shift on a 2- speed. Andy can get away with turning it off before the shift because of the 3-speed, and that's what Kenny bell said to turn it after 60ft but he was running 3-speeds. Bob it shifts at 5200 rpms, want to drill holes in the weights for 5300-5350 rpms. already have the spring off, start out with one hole in each weight on the governor.
The converter has more slip in high stall, and is less efficient. I can't find it now, but I remember Devon saying he either lost time, MPH, or both in the 1/4mi running in high stall for the whole run.
X2 on that. I lost 1-2 tenths in the quarter and 1-2 mph by just leaving it in high stall. The best times I ran, was when I left the line in high stall and hit the switch to low when the rpm was up around 4000. Even when my gs was running the st300. It would slow down at the track when I left it in high stall.
when in high stall never got rubber on the up shift, but in low stall less slip it chirped the tires. there was some 1/4 mile tests with a switch pitch with a pontiac. if I remember right keeping in high stall loss 1 mph not et, and keeping it low stall all the way loss am pretty sure 2.5 tenths. if someone can find and post that test on the internet, its good reading.
found it don't know how to post. it is, torque converters for street and strip-Pontiac. www.pontiacsreetperformance.com/psp/twisting.html
I'm not sure you are gaining anything by turning the high stall back on and then off again around 2nd gear. But I guess it depends on how far the RPM's are falling when in low stall going into 2nd. With the car hauling it already, the car shouldn't fall too horribly on the RPMs and with the torque you are putting down it should pull it well enough in low stall once in 2nd gear. You would just have to make multiple passes at the track and see what works best for you.
I lose about a 10th and and 1 mph leaving in high stall - the idea behind it was to help cars with poor traction. I have a Bruce Roe controller box, I generally launch in high and let the box go to low stall at 3 seconds, or 3200 rpm... chose that point because it's where my HP and torque curves seem to cross if you believe the G-Tech data. Joe - what have you done to the tranny, if anything? I put a PG racing (alto red eagle/kolene steels) 9 clutch pack in and did the blueprint mods to the valve body plate, some 65/66 mix/match in the pump pressure valve and have the governor at 5 k currently - can catch rubber in 2nd at anything over 3/4 throttle, shifts firm and quick.
Do you have that backwards??? I'd expect you to launch in high stall, shift it to low stall after a few seconds.
just a normal rebuilt, no special clutches, had it apart after some hard runs they look real good. drilled out the valve body plate and took one spring out of the governor. shifts at 5200 rpms like to get it to 5350.
I ran switch pitch tranny for about 35 years. Best performance worked like this: Sticky track...............Launch in high stall... count 2 seconds and switch off to low stall. Street or poor track.....Stage in low stall... but, launch full throttle AND switch high stall simultaniously. Count 2 seconds and switch back to low stall. This street method gives a split second to roll start the car, then the power (high stall) kicks in. It happens so fast...it's really cool.
I also have the Bruce Roe box. I highly recommend it. The only thing I did not like about it was the fact that you could not adjust the brake timer to less than 3 seconds. From a traffic light, high stall would stay on for 3 seconds and then switch to low stall. My modified 12" converter's high stall was a bit too loose, and the car was lazy from a dead stop in normal street driving. I talked with Bruce, and he modified the box to go from brake on high stall directly to low stall. I recommend anyone considering Bruce's box to think about whether they would prefer that. The box also has a vacuum switch which puts the converter back into high stall below 4" of vacuum. There is also a number of adjustments to control how long it stays in high stall after the vacuum switch, as well as an adjustable max throttle timer that overrides everything else at the track. It is really a very versatile control unit. The way I have it now closely approximates the way the SP was controlled back in the day. Brake on high stall, low stall off idle, and back to high stall above 60% throttle. At the track, I usually launch in high stall and the box shuts the converter off after 3 seconds. I have never tried high stall for the entire run, but everything I have ever read says that this results in lower trap speeds.
After reading Larry's thread a few years ago, I had mine modified in the same way. Bruce was very accommodating.
never knew this, Carmen was telling me, and he said the converter goes to low stall by itself after 3800-4000 rpms. I did try it a while back, after the shift to high gear and at 4100 rpms I put in low stall with my toggle switch and the rpm did not drop so it was already in low stall like he said. so the thing we are really changing is making it go into low stall after 60ft and to 4000 rpms and then if you keep it off between shifts, that's really the only things that's changing over the stock settings. need to try it in first gear to see if works that way in first gear too or only in high gear.
