Purchasing a Stall Converter

[Dugan]

The question I've been dreading while building my TH350. The trans is now setup for atleast 500HP.

I bought a car with what I was told a 12.8second 400 SBC in it. Ran under a th350 2500 stall 3.73 rear malibu.

I am running a similar vehicle, less weight 84 monte.

I have two options for rear gears in the 9", 4.11 Factory posi, 4.88 spool.

The motor information is unkown sadly. It is a SBC 400 with what appears to be factory heads, aftermarker RPM performer intake and a 770 holley street avenger carb dual inlet single feed carb. I also have a 650 for it. Long tube headers.

Car is gutted for racing still has inner fender wells, but no interior and custom dash.

Anyone have an idea what stall converter I would be safe chosing with little to no information on the car?

I was told it has a .480 lift cam though and the motor with no resistance will rev to easily 6k with a snap of the throttle.

Ive been looking at the 2700-3000 converter here which is 10":
http://www.jegs.com/i/JEGS+Performance+Products/555/60401/10002/-1

But was wondering if i would be safer with the 2300-2700 which is a 12" and usually not for racing.
http://www.jegs.com/i/JEGS+Performance+Products/555/60400/10002/-1
I didnt want to go to much or too little, the 2700-3000 seems good but I thought I would get some opinions, This car will be trailered to the track for fun on test and tune nights with the occasional gamblers races.

 

[projectnitemare]

Without knowing engine specs especially the cam, heads and compression it's going to be hard to give a good choice. Roller or flat tappet? What's the rocker ratio? Nitrous? I can't remember where the SBC head casting numbers are exactly but that is something you should try to look up what you have. In my excerience there aren't all that many great chevy heads. Also the weight of the car is going to be a factor so that will be good to know as well. What size tires are you looking to run? There are a lot of factors for getting the right stall. An out of the box converter can get you close if you know what you have. You have to remember those stall speeds are usually determined for an average fullsize car and it will stall lower in a lighter car. I ran a mild 350 s-10 with about similar specs and pulled a 13.3. To be a drag truck it needed more stall at least 3000. With what you have listed my best guess would be 3000 and will probably need a few hundered higher being it's not a custom converter in a lighter car.

 

[Dugan]

Without knowing engine specs especially the cam, heads and compression it's going to be hard to give a good choice. Roller or flat tappet? What's the rocker ratio? Nitrous? I can't remember where the SBC head casting numbers are exactly but that is something you should try to look up what you have. In my excerience there aren't all that many great chevy heads. Also the weight of the car is going to be a factor so that will be good to know as well. What size tires are you looking to run? There are a lot of factors for getting the right stall. An out of the box converter can get you close if you know what you have. You have to remember those stall speeds are usually determined for an average fullsize car and it will stall lower in a lighter car. I ran a mild 350 s-10 with about similar specs and pulled a 13.3. To be a drag truck it needed more stall at least 3000. With what you have listed my best guess would be 3000 and will probably need a few hundered higher being it's not a custom converter in a lighter car.

Yea, I still have to lift off a valve cover and check that. Ill get the casting numbers when I check the rockers. I believe they are stock components nothing roller.

Not running NOS, and I have a place that will weigh the car problem is transmission is out, no converter, and a few more frame mods need to be done. The car has 26" tires in the rear right now, and 28" up front. I will be going to 28" once these are dead. They were brand new for 100$.

I had looked at like a 3100-3500 stall but didnt know if it would be too much etc.. I wish I knew the cam specs. I guess I could remove the intake, rods, lifters and pull the cam and check for markings?

Ive built a lot of things, but never tore into a motor other then the basic intake and carb, oil pump, timing chain type deals. Just about finished my first trans build and other then the pump bolts being PIA's and the aluminum stripping its been pretty smooth.

 

[Dugan]

I measured the cam off the push rod and multiplied by the rocker ratio. I was getting closer to a 1.6 rocker ratio rather then the stock 1.5s.

I did the math for both. The numbers for the exhaust seem kinda high.

I got .310 for the intake on #1 cyl
and .406 for ex on #1 right off the push rods.

multiplied by each rocker arm and those are the numbers I got. Anyone have any input to if they seem off or what? I did rotate the motor back and forth on those values to make sure the dial caliper wasnt reading wrong.