The car: LS3 Swapped 1989 Formula, 550 crank HP, 440 RWHP.
The cam: 232/236, .600 lift.
The transmission: 4L60E, Yank 3400 9.5" converter

The problem: Tuning issues. The car has been to three different tuners in Vancouver and Tacoma, WA, and the issues have not been resolved.
The issues: Apparent inability to thread the needle between too much idle air (car will idle at 35 mph), and too little idle air (car will have a tendency to stall in certain low speed conditions). The [too much idle air] situation has been tuned out, but the car will stall in some low speed conditions (especially reversing) unless the throttle is managed just right. The latest tuner has arrived at the cam being "too big for what I want to do". For the record, what it is I want to do is to simply not have "hiccups" in stop & go traffic, or, at the very least, to be able to reliably back into my garage or onto a trailer without stalling out.

So, if a smaller cam could solve my tuning issues, isn't it likely that the less-drastic measure of a higher stall, looser converter could also be a solution by allowing more idle air into the equation while precluding the car from being able to run like a bat outta hell at idle?

The converter and transmission experts I've spoken to say that the Yank 3400 stall that I have should be the right converter.
But here I am having these issues and wondering if maybe a 36, 38, 4000 range Vigilante might give the tuners more leeway in finding better drivability for me.

I'm not sure if this thread would make more sense in a Tuning sub-forum. FWIW, the ECU is a factory GM unit from a 5.3 Silverado.

 

What throttle body are you using?

That cam is NOT to big for your Ls3.

Im running a much bigger cam with smaller cubes and mine drives just fine.

Although a converter change will improve your performance with your setup, it will not solve the high idle or stalling issues.

 

The right tuner could solve the problem.
The right converter builder "might" be able to loosen it up down low.
What if it was a manual, it would still stall out when you slipped the clutch while backing up. Therefore why would a 4000 rpm stall speed work better than a 3400 at garage speeds....
It's not impossible to make what you have work.

 

The throttle body is a 92 mm Nick Williams, cable driven.

 

My thinking (rudimentary as it may be) is that more idle air can be added to the equation with the looser converter & higher stall, preventing the car from stalling at/near idle, while still preventing the car from being able to idle at 25-35 mph.

I could be completely off-base, but that’s why I started this thread.

 

The hanging idle and stalling are absolutley tuning issues like Jays_SSZ28 also mentioned.

I really think this should be in the tuning section because that cam is no where near to big for a Ls3 and to try and mask tuning issues with a different converter would be the wrong route to take.

 

Thank you for the input.
However, there is a window of opportunity for me to replace the existing converter without having to pay for any labor costs, as the transmission may be undergoing some repairs under warranty. So, if there were a “more ideal” stall speed, I might can stomach dropping the 8-10 hundred bucks.

I will copy/paste this to the tuning section, as I seem to be getting nowhere fast with the tuning shops in my region.
I say “region” because I have to drive a minimum of 2.5 hours to get to a tuning shop which makes this all the more frustrating.

 

We have a way bigger cam than you. Not sure if this is your problem or not but we had a Yank 3600 stall. The motor would cough when you would come off the brake then rip, or just stomping on it too. Tried everything tuning wise. Got it close but it would still cough at launch. Finally called and talked to Yank and he said it needed to be loosened up but was 2 months out for return. Then I found out Coan was like an hour from my house and called them. They suggested a 5000 stall so we ordered that and was at our house in 4 days. Went from a 1.49 60 with a cough to a 1.27 without a cough just from changing the converter. No more cough in the least bit. Funny thing is when your not into it and just driving around, you can't even tell there is a stall. Yank was the same way driving around wise until you would hit it. I'm sure Yank could have done the same thing stall wise, but we didn't want to wait that long. The 5000 stall nitrous converter would take 900 fwhp but anymore it was too loose. Ended up tightening it up to 4500 and now it will take 1000 fwhp without blowing through it. We played with the 2step to see how low we could go on the launch before the cough would come back. We could drop it to 3600 before it would come back. 3800 and above no cough. We usually lauch at 5000 now on a decent track and only back it down to 4500 on a bad one. Hooks real good.

 

I agree with this and the other similar comments above. IMO, the real solution, although it will involve a chunk of money and a lot of time, is to purchase a tuning suite (HPTuners or EFILive) and and start playing with the idle air settings until you make it work.

There is a ton of great advice available out there. This will likely require a fair amount of tweaking to get right, and that just can't happen if you have to drive 2.5 hours to a tuner who is not going to take the time to tweak as needed. Or if he does, it'll cost as much as the tuning suite anyway.

 

you have a 3600 converter on an LS3 and only 232 degrees of intake duration...and your tuners are saying that the cam is too large? Really?
Find new tuners...

 

Make sure that you do not have a vacuum leak... They can be a huge pain to find sometimes.

 

^^^ that. A vacuum leak will 'confuse' the computer. A slight vacuum leak is like the throttle body being slightly opened, but that extra air will be read by the O2 sensors and increase gas amount for proper ratio. But since that extra air is not coming thru the MAF, that's where computer confusion occurs.