I'm not sure about it, so I'm trying to learn about the torque converter matching.

The first one was making the car pull a lot harder,(Yank 2800) but I know it's not the right one and it was made for a boosted vehicle (truck) according to the seller, but it felt way better IMO. This one is more responsive, but I think too high for what I am doing with the car. I think it's a TCI about 4000 and accelerates good, but no pull to it, not as fun.

I'd like to try to learn how to really match the stall to the cam, weight, tires, and gears. Does it change how it acts between carb and EFI? The car is carb now, but someday might be EFI again.

So from what I know...

Intended purpose: Street car

Weight: 3300? (lots removed, but heavy bars in place) with out my 300 of course (but might remove more stuff) at best maybe someday 3200? with hardtop off and soft top removed it's less.

Engine: 434sbc

Trans: built 700r4

rear gears: 3.45 (would like 3.73, but hope to not change unless I have to)

Tires: 26"


Cam: 2,800-6,500 rpm
296/302, Lift .600/.600, (.650 lift now?)
Rough idle, Hot Street/strip, good midrange torque.


I think I need to be closer to the first stall. I'm open to any thoughts or experiences, I know it is a real science for people to get it right, but most times lots of variables with stall converters.

I'd like to know if anyone here figured it out.



The shop that sold me the engine suggests "3200-3400 max and a 3.73- 3.90 gear and the car should really wake up, but for sure lower the stall to that"

 

I don't know how much help I'll be, but i went through some of this trying to decide on a new stall for my car.

I was told that you target your stall where the engine makes the most power.

From there the converter will do all of the work in between.

I went with a 3200 rpm stall in the end, but i get what they were telling me now.
no matter what gear I'm in, if i punch it, i have instant acess to the powerband.

If i had gone with a higher stall, that instant acess to power would have been greater.

It's still a weird feeling, it almost feels like clutch slippage...

 

Also, if i were to do it over again, i would still pick the 3200rpm stall.

i also like that i can do a little engine revving while in gear and driving down the road...

I pretty much use it as my horn...

 

One more thing, think about where your envine really starts to pull.

For me, i noticed an almost boost, or 2stroke dirtbike power band beginning at about 2900-3000rpm, so i put my stall a tiny bit after...

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I'm not totally sure to be honest. I'm just not been analyzing the car that much until lately. I was just happy it was built and running due to Bjankuski. Now it's time to think about maybe dialing it in, I spent too much to not finish it right and enjoy it's full potential.

It was on the dyno, but it was not running good and shutting itself off, so hard to tell, but if I remember it was making like 525wtq at 1800 rpms? IDK anymore, but I know that was on fuel injection with a stock plenum on top of a carb base. Now it's carb, intakes can change alot of stuff too.

Either way the cam is a little on the low end I think for this stall and unfortunately the gears I have always felt are a little tall, but great compromise for normal driving and still able to be fun.

I agree about the access point, but it's too far past the good torque I think. The car really used to pull hard to me from down low, but the stall was just a tad low for the motor, then it would come on hard to me, or even the tires would just start to rip off. Now it will blow them off of course, but the thing just accelerates, and you don't feel the g's. Hard to explain.

I think this is where stick really is a major advantage, really takes out a lot of variables that can interfere with a car's character.

 

If it helps any...

My camshaft specs specified power 2600rpm - 5500rpm if i remember correctly...
i felt that in the seat pretty close...

 

This ^^^ I don't do this much, but I sell a lot of them.

Ideally it's matched to the cam. The guys want them to flash up into the power band like Gibbles says.

 

Okay, so as i posted my cam is rated 2800-6500, but the 2800 stall I had was not perfect, but could definitely use the torque better.

Since you sell them,.. What are your thoughts?

The race shop I bought the motor from said gears alone with even the 2800 would not make it right, they said 3200- 3400 and gears would make it work right. They are active in all types of racing in the business and personal lives so I have to somewhat trust them.

Maybe a proper set up 2800 for my car would work better?

This is the part I am missing, The only thing I can think of is the way the yank was set up was not quite right for the weight and power of the car.

Again it's not a race car, but obviously you can tell the parts are not a matched combo.

 

I install what customers ask me to. I typically recommend they interface with their engine builder, because the power curve of the engine is the determining factor when selecting stall speed.

But, advice from what I have seen here? If you think the Yank pulled harder.. Take what you have to the track and then try the Yank again and compare.

The fact that it is a "truck" converter is of no consequence whatsoever. One of the favorite mods when we were kids was the Chevy Vega converter in our TH350's. Many of the S10 Truck converters are employed here just because the quality is high, and so is the stall speed.

I am at a disadvantage here because I don't race, but if I had to make a choice, it would be something in the 24-2800 rpm range for a street car.

 

PS: Stall is slip, and slip is heat. It should have a trans cooler.

There's all kinds and they give you vehicle weight calculations and such. But in a temperate climate? Ignore that. Just use the biggest one that will fit.

WAY UP NORTH, over cooling may become an issue, depending? But anywhere else, you're fine.

 

Thanks, I have a larger transcooler and the track, would be interesting, but I know this stall will get as good as a time or better, but I can't feel the toque. Hard to explain. No real throwing you back in the seat, the other one did. It felt like a muscle car, this just moves out quick.

I have it for the sound and feel, not times, so to me even if it was slower at the track with the right stall, as long as it was fun driving it I'm happy.

I can always add power to go faster, I just want to feel the going fast I already have. Must just be a little high is all.

I guess that is the other thing, I don't know if the other one was tight and this is loose, not sure but definitely there was like no slip in the other one.

So is that based on slip, or something else when they say tight or loose? For example: can you have a tight 4K stall ?

One more point... the other stall was rated for like 400hp I think, this TCI I'm not sure, but I know the guy I got it from here ran like 600-650hp through the TCI. My motor is "supposed to be" 650-700 on the stand. What I mena is how does power affect how something stalls? If I get a trans that can handle it and pump 1000-1200 hp using nitrous how will the stall act?

 

In my experience? No..

There's a couple of different ways of explaining fluid dynamics in a torque converter, but when you are talking about stall, all of them boil down to: It's doing very, very little in terms of moving your car till it approaches that number. It is horribly inefficient (And builds a LOT of heat as a result) till it approaches that number.

I can't imagine a street car with a 3500 RPM converter.. Let alone 4K

IMO, no.

 

Okay, that makes sense now.

 

Power doesn't change the stall much, if at all. It's about vanes in the converter housing.

There is a part of the converter called the stator, and it has a one way clutch on it. It's a sprag type clutch. It's complicated, but you can think of it as what you "launch on" for practical purposes.

NORMALLY, this isn't an issue. With your power levels? The high HP converters probably have a stronger clutch.

 

With those power levels, if you overpower the stator clutch? You don't go anywhere.

So, it is an issue for you.

You want an HP rated converter.. Because you're way past stock, or even hot, and out there in lala land.

 

Okay, so maybe that explains the ******* out of the hole with the 2800 stall, until it caught up and pulled hard, almost like boost kicking in on a small motor.

 

No.. That's the powerband.

If you overpower this clutch even once? It blows up and you stop..

Right now.. It explodes.

You will not slip a sprag clutch for very long till it just fails catastrophically..

 

IMO, Talk to your engine builder. That guy can recommend the perfect stall. Then buy a high quality converter to match.

 

I appreciate the help.

 

I'm sorry I don't know more.

I don't do a lot of race stuff here.

But if I can help with some question, PM me..

All the best!