Torque Converter stall question for 86' ho 5.0 in 73 bronco

[aklb43]

Hi Guys,

I have an 1986 mustang 5.0 HO stock cam with GT40 heads in my rebuild. Turns out I need a different torque converter to match the bolt pattern on my flex plate, so I'm taking the opportunity to match the stall speed to the engine/cam. Seeming that the Stock cam in a mustang has torque/hp curve further up the rpm range than a stock bronco cam, I'm considering moving the stall of the converter up to 2500 rpm, per suggestions I've read in mustang forums. No, I will not be on the trail unfortunately. I spent to much on this restore to go off road, so it will remain on the street.

What are you guys thoughts on this?

 

[brewchief]

Make sure you have the proper flexplate as well, I understand needing to swap the converter due to the oddball bolt pattern on the converter but make sure the tooth count on the flexplate is correct as well, mustang could be the 157 and the bronco sbould be 164.

Stall speed isn't an absolute, a converter sold as a 2500 could be higher with a heavier vehicle and more power or lower with the opposite. I wouldn't be afraid of a 2500 stall converter but there are some guys that would hate it.

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[aklb43]

Make sure you have the proper flexplate as well, I understand needing to swap the converter due to the oddball bolt pattern on the converter but make sure the tooth count on the flexplate is correct as well, mustang could be the 157 and the bronco sbould be 164.

Stall speed isn't an absolute, a converter sold as a 2500 could be higher with a heavier vehicle and more power or lower with the opposite. I wouldn't be afraid of a 2500 stall converter but there are some guys that would hate it.

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I have the correct 164 tooth 50z flex plate.

Why would they hate a 2500 rpm stall?

 

[toddz69]

I have the correct 164 tooth 50z flex plate.

Why would they hate a 2500 rpm stall?

Some people would consider that to be too high a stall for your truck. It appears you have 33" tires and I'm not sure what gears you have. I can tell you that I had either that stall (or maybe it was a 2300 rpm stall, I can't remember for sure) in my truck for about 7-8 years when I had my C4 behind my 91 5.0 HO. My trans guy looked at the 5.0 cam specs, my gearing, tire size, etc. and intended usage and determined that stall speed for my application. It worked well for me on and off-road. No overheating.

Todd Z.

 

[Broncobowsher]

Tire size and gear ratio are HUGE variables.

2500 stall is probably going to be too high. Mustang forums are generally going to give information based on quarter mile times, not off-road performance. All that matters to them is full throttle as they are driving through a crowd of bystanders.

The stock mustang cam really isn't a HP cam. It is a good lower RPM torque cam.

For a Bronco you are going to generally have better performance with a stock or +200 RPM over stock convertor.

 

[aklb43]

Tire size and gear ratio are HUGE variables.

2500 stall is probably going to be too high. Mustang forums are generally going to give information based on quarter mile times, not off-road performance. All that matters to them is full throttle as they are driving through a crowd of bystanders.

The stock mustang cam really isn't a HP cam. It is a good lower RPM torque cam.

For a Bronco you are going to generally have better performance with a stock or +200 RPM over stock convertor.

I looked at the powerband for my engine/cam and it started to output power around 2300 rpm. I'm not doing any off roading and my engine doesn't have an RV cam. My gears are stock 3.5:1 and my tires are 33s. The stock gear ratio for the 86 mustang was 3.27, so not to far off from what I have. Only big difference between my truck and a mustang is 33" tires. I'm just looking for a good get-go off the line at this point, since my truck will never see the trail due to the amount of money I threw at it.

Also, regarding the stock mustang cam, I intend to upgrade eventually.

I think the idea is to have the converter stall at an RPM when your HP starts, and looking at the graph below in the link, I should have my stall up around 2800-3000, which is what the mustang guys were saying. But, my torque converter dealer said he can only make them up to 2500 rpm stall, so that's what I was going to go with. Being the gears are slightly taller, im thinking the tire height will even things out to perform more like a stock mustang, but thats a guess.

http://www.dragtimes.com/1986-Ford-Mustang-Dyno-Results-Graphs-20608.html

 

[aklb43]

I just talked to Superior Torque in Oregon, which I was referred to by Wild Horses. They said stock stall will work best, so that's what I'll go with. He said they only stall out the converters at higher RPM with high HP engines so they don't lurch. WH also doesn't have the flexplate that mates upto a 10.5" pattern converter anymore, so I have to buy a converter. Turns out most places don't have a 26 spline 11 3/8 pattern converter, which is what I need, so I have to have it built, unless you guys know of something I can pull it off of from the local yard.

 

[Broncobowsher]

FYI, the stock 3.50 gears and 33" tires are not going to be happy with a C4. That gearing is good for stock size tires. Running 33s is a lot more fun with 4.10 gears.
The 4.10 gears will make the Bronco drive much like it did when it had stock size tires and the 3.50 gears.

I will agree with the convertor shops suggestion of a stock convertor.

 

[aklb43]

Dang, good to know. I'll have to fix that.

 

[aklb43]

I cant seem to find a 26 spline 11 3/8 bolt pattern torque converter at the regular parts stores. Is this something I have to have made by a transmission shop?