tech question

[davidhicks16]

I guy I work with has a 84 dodge 4x4 pickup. He has a 360ci crate motor roughly 400hp, It has 4:56 gears, 35/12.50/15s, 3800 stall, and a 3speed auto trans.
The truck is freshly put together and we are trying to get the kickdown adjusted. What I need to find out is what kinds of speeds and rpms this monster should be shifting at?

 

[IZwack]

It should probably be shifting at stock RPMs but I think that torque converter is mismatched - too high. Stall speed should never match or go above the engine's peak in the RPM curve or else the engine's power becomes useless. So unless that engine redlines at 12,000 RPM, I'd say a stock torque converter will probably be more useful.

 

[davidhicks16]

Im thinking that's not what he will want to hear.
he was running this same set up about a month ago and his trans blew up, It took out the floor pan when it went! You think that high of a stall could be the culprit?

 

[Maniak]

With a 3800 rpm stall speed that converter will not be anywhere near hydraulically locked up when cruising down the road. That means it'll be generating tons o heat.

~Mark

 

[davidhicks16]

What kind of converter should I direct him towards?

 

[Maniak]

What is its intended use?

Assuming its going to be a DD, figure out the rpms it will be turning on the freeway and make sure its stall speed (actual stall, not advertised) is less than that.

Also, you want to know what the torque curve is on that motor. You want the stall speed to be lower than the peak torque of the motor.

~Mark

 

[IZwack]

The stock RPMs - usually in the 1500 range.

 

[davidhicks16]

Do you think the paper work that came with the motor will give us good info? Or should we get the thing on the dyno?

 

[Maniak]

You would be safe going back to a stock converter especially if this is a DD.

If it was a race type rig then you would want to get the stall speed up some so you could get into the peak power sooner which would mean dyno it if you don't have the paperwork BUT I doubt that is the right way to go in this case.

~Mark

 

[davidhicks16]

Yeah It wants to be a mud drag truck, but all and all its a dd