Changes are coming for the Road Runner.

Hurt the crank/rods/bores last year, so I will be replacing the rotating assembly.

Current setup is 0.030 over 440, OOTB Eddy Heads, 0.557 Solid cam, M1 Intake/950 Holley. Drive train is a 727 with trans brake, 8" Turbo Action convertor, Ford 9 inch with 4.11 gears.

3600 pounds with me in the seat.. Runs 11.00 on 275 Drag Radials, 10.80 on slicks.

I am planning to bore it a little more, and 4.150 stroke to crowd 500 cubes.

So, I am expecting more power and torque.

Still debating a gear change (3.89), but my question is how is the small torque convertor going to work with the horsepower and torque changes? What will happen to the stall speed?

Any insights will be appreciated.

Thank you, John

The stall speed is obviously going to increase, depending on by how much, may require an adjustment.

Stall speed will go up since you'll have more torque. If you are keeping the same top end (heads, cam, intake) then the power isn't going to increase much if any, but the torque will increase. By keeping the same top end but putting it on a bigger bottom end you'll run out of air faster. A gear change may be required depending on where it was running out of air before.

Switching to taller rear gears will make the stall even higher so you'll have to keep an eye on it.

look at using the 4.25 stroke kits with 2.2 rod journal sizes and 7.100 long BB Chevy type H beam forged steel rods and pump gas pistons, more HP and more torque
Maybe cheaper too
That combination works real well
As far as the converter working with the new combination why not leave it alone until you try it with the new motor
I have own and driven a bunch of different sizes and brand torque converters on the street and at the track.
The best one was a Turbo Action 8 inch Super Stock hemi automatic built for a NHRA SS/AH 1968 hemi Cuda race car, IT WAS GREAT on the street And great at the track also
The worst was a 10 inch Art Carr, street and strip, it was horrible

I agree with Cab. Also that cam will be on the small side for a 500 inch motor.
A bit taller drag radial might work better instead of a gear change, if one will fit. You can add a fair amount of cam duration and with a little luck it might even come close to a match with the converter. If not, you will have some info for a stall change.

Stall will go up and slippage will likely increase.

Drag radials are typically quicker & faster than bias-ply slicks. Is your chassis not dialed in for radials, or are your slicks taller and allowing the car to pull more MPH --> lower ET? A 2 tenths difference in favor of the bias-ply slicks only makes sense to me if you're over-geared with a shorter drag radial, which is exactly what I ran into years ago switching between 275/60R15 DRs and 9.00 x 29.5 slicks. The car was .2 quicker and 2 MPH faster on the taller tires cuz I was over-revving it on the big end with the shorter radials.

We run a really mild 11", 2800 stall RATED converter with a 3.54 gear behind our 505" stroker.
Still manages a 1.36 60 ft. on a small shot of spray. Usually mid 1.50's N/A.

What did it flash before? The stall is going to be higher but I bet it will be fine unless it was on the loose side with the 440. And IMHO many times over the years I have seen people size and stall converters too tight to begin with.

Like I always say loosen it up to the point you cant tell if the car shifted or not, then tighten it up a couple hundred, and roll with it...

Thank you all for your knowledge.

Plan is for a larger cam - 0.600+ lift and more duration. I have not bought rotating assembly parts yet, so going a little bigger is still an option.

Slicks are 30.0/10.5R-15 - Hoosier radial slicks. I may not have to change gear ratio.

I have never put the convertor on stall, so I am not sure.

At this point, keeping the set-up the same is probably a good game plan. If it does not work, start with a convertor change after testing the stall on the current set-up.

Thanks again for your input.

John

Nice looking car. It is all related so if you change one thing you end up changing other things. If you consider that fun then you'll have lots of fun. If you hate working on the car then you'll hate all the work!

Great looking car, John! Good luck with it. 👍

We moved from a 528 to a 572 and used the same converter that was originally built for the 528 by ATi. Rear gear / tire was also the same. The H/P difference was initially around 100hp, in favour of the 572. It worked fine, as has been said, we picked up 3-400 on the flash stall footbreaking the same. Going from 10.00 to mid 9's (135 - 142mph) the car put on some weight with the extra safety gear/ more cage and further mods. The converter was on the list to change but it worked good so it stayed.
HTH's

Thanks all for the comments.

I will give it a try with the current converter. If it does not work, not a lot of work to change it.

John

If you dont mind me asking, what is the part number on the Turbo Action Torque Converter? Just out of curiosity.

I agree with others who said keep running the same converter with the new combo. Everyone on my race team have gone from smaller cubic inch big block engines, to larger big block engines, and continued to ran the same Turbo Action converter with both combos. They worked just as good in the smaller engines as they do the big engines. We all run Turbo Action 8" opel converters. They are all fast and consistent.