I finally got to drive the car with the new TH400 earlier in the week. The tranny shifts very smoothly, not an issue at all, so to Carl Rossler up to this point.

The converter was loose, but quite tolerable. Yesterday, I finally got around to where the car was running well enough to try stalling it against the brake and oh my, it stalled at about 5,200rpm . I would have thought this would be absolutely undrivable. Coan insisted it would be ok, and I guess they were right. OTOH, I think it will be way too loose at the track anyway, in spite of nearly an hour on the phone with them and the intent for it to stall at ~3,500. It looks like they gave me what they thought I needed rather than what I said I wanted. OTOH, they were right about the drivability, so I'm going to try it at the track before bitching them out and having them "tighten" it up.

Anyone have any thoughts to share? Are you using a converter this loose on the street? Know anyone who is? How's it work at the track? How much can a converter typically be "tightened up"?

Rich Krause

 

5,200 brakestall!!! Let us know how it works at the track, but I think you may want to get the stall lowered. I'm running a puny 3,600 stall, but it drives great. What new cam did you go with Rich?

 

Let me know how it does, I'm going to increase my stall up to 4000, during the shifts the car comes out of the power band than get backs into it.

You really want to keep the car in the power band all the time and not let it get out of it. Now with that said there are trade offs between daily street driving car and track car. Mine get driven to the track and back home and that's all, so for me the higher stall would be ok, but for someone that has to drive daily with the stall it might not be the best option.

Good luck, looking forward for the results.

 

I have a "loose" converter and I drive it on the street and have no problems. I am using a B&M plate style cooler and do not run over 150 degrees tranny temp even in 90 degree heat in traffic. My converter is a 9" nitrous converter and stalls to ~4200 on the transbrake on the motor and should go to ~5200 rpms on the bottle. At the track this converter is great although it is tight once it goes past 4200 on the motor. It should be a different story once I hit it with a 250rwhp hit. I like it and I was in the same position as you are and thought it would be unstreetable and too loose but was assured that it was made for the combo and would be streetable (and it is). What is cool about a high stall conveter is the increased ability to adjust your stall by feathering the gas pedal on the street and lay into it without spinneing your a$$ off...very good for the street. I'm sure you'll be glad they sent you that stall instead of the one you wanted.
Later
Matt

 

I 2nd Matt, the high stall is great when you make big power.Ive had little trouble driving my car with a 10"3500 stall as well as the 8" 4800 stall..I did a lot of traffic driving in philadelphia too..I thitnk it depends on the brand you use..I tryed to run a GER junkverter..(he was local) It went through tranny fluid like a sommamabitc .Damn thing acted like a light switch too.Your gas milage sucks in traffic but tehn again you probally arent worried about it much.Thats the only difference..Only problems in general are explaining it to cops who think ive scooted out of toll booths before..

Then i went with a tried and true unit from Select Performance..I grew up with his son so i knew it would work..I suggest that you get a trans temp gauge and the biggest cooler you can fit..Not to say that your choice of stall would be better.But remember there are a lot of other variables with a converter to change..Torque multiplication ratio is one that you should ask about..They may have gave you a 2-1 ratio and for some reason couldnt get that with the lower stall unit..Or they may have went with a 1.5-1 ratio and the higher stall.After you take it to the track and feel that you need to change it then ask them abnout the ratio.

 

I've gotta say again, I was amazed at how nice it drives on the street. I mean, it's kinda odd but nothing I can't live with with the kind of driving I do. It wouldn't be fun for long periods of "stop and go" though. Coan insisted that the technology of converters has changed, and they have made at least a partial believer out of me. Can't wait to try it at the track. Should be "interesting".

The cam is CC XE HR lobes #3192/3196 on a 116LSA. 224/236 @ 0.050" with .567/.585" lift (1.5). It runs great, but as I said I can't say how much hp it makes. A chsssis dyno does not give accurate hp readings with a converter this loose, though it can still be used for tuning.

Rich Krause

 

Rich, IIRC you are shifting in the 6500-7000rpm range correct? This sounds like a solid setup, so long as the extra torque on nitrous) doesn't make you drive through the converter.

I often see converters being treated the opposite of many aspects, in that more stall can actually be better, (Unlike Cams, etc). JMO but a 3500 stall would plain suck.

Is this a 9" or 10" converter?

Oh, and I wouldn't call this a super high stalling converter.

 

Kurt: it's a 9". I am planning on shifting at 6,500, but there's no reason I couldn't shift a bit higher it that turns out to be faster. An option will be to may use the nitrous only in high gear. Or perhaps 2nd and high.

Rich Krause

 

AS long as you can hook it with that big a converter I doubt it will slow you down. WE have tried many converters in my dads Procharged BBC and as long as it doesn't drive thru the converter the looser on always worked well but traction is an issue with our car b/c it makes over 1,00ftlbs of torque at 5000rpms. We had to put a tighter converter to be able to hook up and not drive thru the converter. I bet you will be ok but only one way to find out. Keep us posted. later Clint

 

After some more dyno testing, I decided not to take it to the track. As you posted about traction problems, even if it would pull through the traps, I realized it would simply not have enough traction to launch at 5,000rpm. It has nearly 900ft-lbs at the rear wheels and I a running a 27" tall 10" tire. I'll bet your Dad's BBC is running a tire wider than 10". But it was truly surprising that I could have driven this one on the street. Maybe that piece of information will be useful for someone.

BTW: it took over two hours to get that tranny out. The bolt at the upper left had next to no clearance from the floor pan. We had put it in with the motor, and didn't think about taking it out! I am going to drill an access hole, which will save about an hour next time.

Rich Krause

 

JMO Rich, but instead of slowing the car down, why not try to find more traction instead.

Unless you're cutting 60ft times well into the 1.3x range, I think you still need to put in some work in that area.

Even if you are traction limited, you could possibly use a chip on the launch, to calm it down, or the converse, having that much power may hit the tires hard enough for it to actually get traction. Its a fine line, to having enough power to get traction, and not too much or too little. Seems odd you can have too little power to get traction huh?

I know you try to keep this thing streetable, so I don't know what your suspension consist of, but I think there are enough products out there that would let you make do, and keep the car streetable.

 

Check out the Firebird on BMR's website. www.bmrfabrication.com
1.3x 60 fts on 9 inch slicks. It can be done. I would give it a try at the track before you give up on the high stall. You may be surprised. Also, there are a lot of NHRA/IHRA stock class racers pulling the front wheels on small slicks. All with bolt on traction devices.

 

I appreciate the adivce from experienced guys like you! But you should have seen it on the dyno once we really got on it. After cracking the throttle, it would flare to ~5,000rpm and sloooowly accelerate. The motor was running strong, with 15psi of boost. It makes at least 700hp without the N2O and we were getting readings in the mid 400's . The logical explanation is that the converter was slipping like crazy, the dyno measures hp by how fast the drums accelerate. At 6,500rpm the wheel speed was only 100mph, so it would never go through the traps, especially considering that the dyno has a lot less inertia than the car, and we weren't even spraying it.

We have tested high stalls before, and the behavior is similar. But this was really exaggerated.

Rich Krause

 

Sounds like it was driving thru the converter exactly what KT and I said may happen. Looks like you will need a tighter converter. We put a 5k converter in my dads car awhile back and it would stall to 7k on the transbrake . As soon as i put it to the floor the shift lite would come on way too loose. Converters are almost never right on the first try with these kind of setups. Goodluck.

 

Rich, I read your post a couple times, and it seems its driving through the converter just as T/A LT1 noted.

A couple options:

-Get the 9" Tightened up

-Try a 10" unit.

Obviously we know which one is more cost effective.

FYI, I am using a Chance 10".