Torque converter recommendation

[Daniel]

Hello all. I'm glad to join. I have lots of questions...hopefully not all stupid.

My first question involves the torque converter. I need one. I have yet to order a torque converter or rear gears for my project. I used the search tool to look thru the forums to see if anyone had asked my particular questions to no avail. So here goes.

I know there is a direct relationship between the cam and the converter, so I'll try to provide as many details as possible.

My build is a Spirit Cars '23 t-bucket
Turbo 400 tranny
Olds 400 big block bored .125 over to a 427 (4.0"bore x 4.25"stroke)
Compression 10.25:1
Edelbrock heads: heart shaped chambers, 2.072" intake/1.68" exhaust valve sizes
Offenhauser dual quad tunnel ram with a pair of Holley 4160 600cfm carbs.
Cam specs: Crower flat tappet .464/.485 lift 108lsa with 228 intake/238 exhaust durations. Powerband begins at 2500rpm.

Rear tires are Mickey Thompson 29"x18".
I have yet to determine a rear gear ratio.

Does anyone have any advice or recommendation for a torque converter? When I called different manufacturers such as TCI and B&M they recommend similiar 2200-2600 converters. However, when I called Boss Hog I actually ended up talking to the owner of the company. He gave me a recommendation (Boss Hog Bandit 47015) after asking lots of detailed questions that the others didn't ask, but more importantly he recommended going down a rear gear size for every 1.5 inches of tire diameter over 26". So in my case with my setup a 29" tire at 60mph would get me 2579rpm with a 3.71 rear gear. Keep in mind that my powerband begins at 2500rpm. So he recommended dropping two gear sizes going from a 3.73 or 3.9x to a 3.4x-3.5x rear gear. But with those ratios the rpms are slighly below my powerband. Can anyone validate or refute this info?

A proven converter/rear gear ratio with a similiar setup would be a big help.

Also, would anyone care to venture a guess about the weight of the vehicle?

Thanks in advance.

-Daniel

 

[fletcherson]

Weight guess around two thousand, from what I've heard on average. Spirit likely has more accurate info as they know their product. The light weight will also figure into your converter as far as lock up. There have been several guys experiencing the car pulling at idle (like at a red light)with a lower stahl speed, so when you narrow it down, keep that in mind. Also keep in mind, with your power band, are you figuring the rpm in second gear or third? You will likely downshift at that speed to hammer down, so that may change your numbers a bit. olds is a torquey motor, you shouldn't have any lag at lower rpm, within reason.

 

[Swampdog]

You are going to find torque converter recommendation are like , well everyone has one I have a 350 SBC with nearly the same cam. It has 3.25 gears and I originally has a stock converter but I replaced it with a Hughes GM25, which is a 2500 stall in some vehicle. It really woke up the bucket. It flashes about 2500 rpm. I would add to consider getting one that is furnace brazed. I would think that would work for you.

My bucket weighs 1980. (that not what I think it weighs, that is what it weighed at the feed store). I would guess that yours may be 60 pounds heaver .

With a 4.25 inch stroke I would worry about the piston speed with a low rear end ratio. With the torque that thing will make I wouldn't go lower than 3.50.

 

[SRM1952]

Hello all. I'm glad to join. I have lots of questions...hopefully not all stupid.

My first question involves the torque converter. I need one. I have yet to order a torque converter or rear gears for my project. I used the search tool to look thru the forums to see if anyone had asked my particular questions to no avail. So here goes.

I know there is a direct relationship between the cam and the converter, so I'll try to provide as many details as possible.

My build is a Spirit Cars '23 t-bucket
Turbo 400 tranny
Olds 400 big block bored .125 over to a 427 (4.0"bore x 4.25"stroke)
Compression 10.25:1
Edelbrock heads: heart shaped chambers, 2.072" intake/1.68" exhaust valve sizes
Offenhauser dual quad tunnel ram with a pair of Holley 4160 600cfm carbs.
Cam specs: Crower flat tappet .464/.485 lift 108lsa with 228 intake/238 exhaust durations. Powerband begins at 2500rpm.

Rear tires are Mickey Thompson 29"x18".
I have yet to determine a rear gear ratio.

Does anyone have any advice or recommendation for a torque converter? When I called different manufacturers such as TCI and B&M they recommend similiar 2200-2600 converters. However, when I called Boss Hog I actually ended up talking to the owner of the company. He gave me a recommendation (Boss Hog Bandit 47015) after asking lots of detailed questions that the others didn't ask, but more importantly he recommended going down a rear gear size for every 1.5 inches of tire diameter over 26". So in my case with my setup a 29" tire at 60mph would get me 2579rpm with a 3.71 rear gear. Keep in mind that my powerband begins at 2500rpm. So he recommended dropping two gear sizes going from a 3.73 or 3.9x to a 3.4x-3.5x rear gear. But with those ratios the rpms are slighly below my powerband. Can anyone validate or refute this info?

A proven converter/rear gear ratio with a similiar setup would be a big help.

Also, would anyone care to venture a guess about the weight of the vehicle?

Thanks in advance.

-Daniel

hello

when this guy from converter company said drop down on rear axle gear---did he explain what he meant --when most car guy say drop down in gear it would be to a larger number. Like 3.70 to 3.90 or 4.10 not to a more highway gear like 3.4 or 3.5 . When going to a taller tire one would go to a lower gear ( bigger number ) .

Just make sure ,no miss under standing . Because of the light weight of a t bucket 1800---2000 lbs a higher stall speed converter maybe needed so as not to fight the converter to stop and hold car slowing down and a stop lights.. Stall speeds are at lower speeds the lighter the car gets ex. a 2500 stall may pull hard at 200 rpm in a light car .

 

[Daniel]

Thanks for the replies.

SRM1952, when I talked to the gentleman that recommended a lower gear ratio, I thought what you mentioned....that he meant 3.90 or 4.10....so I asked him what gear he would use if it was his project, and thats when he said 3.4x or 3.5x. This threw me for a loop. I think it would be wise for me to call again and see if I was right.

Fletcherson, the rpms I quoted in the initial post were for 60mph in 3rd gear. I was always under the impression that you wanted to be at the bottom, but inside your cam's powerband when cruising in the tranny's final gear to prevent surging and downshifting...I might have that wrong though....

Anybody have a converter that works for them with a similar setup... a TH400 mated with a torquey motor in a bucket???

Thanks

 

[fletcherson]

Thanks for the replies.

SRM1952, when I talked to the gentleman that recommended a lower gear ratio, I thought what you mentioned....that he meant 3.90 or 4.10....so I asked him what gear he would use if it was his project, and thats when he said 3.4x or 3.5x. This threw me for a loop. I think it would be wise for me to call again and see if I was right.

Fletcherson, the rpms I quoted in the initial post were for 60mph in 3rd gear. I was always under the impression that you wanted to be at the bottom, but inside your cam's powerband when cruising in the tranny's final gear to prevent surging and downshifting...I might have that wrong though....

Anybody have a converter that works for them with a similar setup... a TH400 mated with a torquey motor in a bucket???

Thanks

Here's my take on the power band, and I have checked several manufacturers sites to verify that I am not misleading anyone. The power band is where the cam will produce the most power. Sort of like those old two stroke bikes, it will still make drivable power below and above, it's just optimum in those ranges. Ideally you want to run in that range when you want the power, but in the example of cruising at hi way speeds in a light car with favorable gears and a torquey engine, you won't need the optimum power, so running a bit below is no problem and will likely save some fuel. When you want the power, like to show that punk in that new mustang next to you what's up, you will downshift, now you want to be inside the band, and in my preference, be near the bottom of is so I can use as much of it as possible before shifting so I can optimize all of the advantages of the cam and gears, but that's my preference. In my way of thinking, if the car is cruising in third gear inside the power band and I step on it, the downshift will raise the rpm and basically eliminate a chunk of the power band, limiting the cars potential power by shortening the band. If it was a heavy car or a truck that has large tires or pulls a trailer, I would want to be inside that band at cruising speed. It all depends on the purpose of the car, when you need the power, what your driving habits are, etc. There is a "Hugh's" site that does a good job explaining it if you want to look at it.

 

[Indycars]

but in the example of cruising at hi way speeds in a light car with favorable gears and a torquey engine, you won't need the optimum power, so running a bit below is no problem and will likely save some fuel.

My Crower camshaft(560 lift, 236° duration) starts to really come on about 3000 RPM, but on the highway at 1800 RPM at 65 mph I'm getting over 20 mpg. At 75 mph it drops to about 18.5 mpg. Therefore you are right about cruising at an RPM lower than your powerband.

 

[409T]

A proven converter/rear gear ratio with a similiar setup would be a big help.-Daniel

I have a 327 with a turbo 400, 3.55 rear end and 31" tires. Actually it is in my wife's T-bucket but that is another story. You can play all day with cam lift, duration, expert information from people who have never even seen a T-bucket, and so on, I guess that's what makes horse races. My wife's T-bucket now has a 3200 rpm stall converter and she loves it. With the original (I'm going to guess "stock" what ever that is) converter she had to use both feet on the brake pedal at a stop light to hold the car. The 3200 rpm stall converter solved that problem. You would be fine with that setup, but I have 3.89 gears in my T-bucket (409 engine) and I like that much better. I almost forgot, congrats on the Olds. If you ever get tired of it PM me.

 

[Daniel]

Hello all, I have an update.

I talked once again to the owner of of ACC Performance, Nelson, about his previous recommendation of his Boss Hog Bandit torque converter. He recommended a converter (47014)... he explained to me that the specs on the converter say that it stalls between 3600-4200rpm (those specs are for a vehicle weighing 3680lbs), but because of my weight it will stall between 1800-2000rpm and will fully flash between 2600-2800rpm. Furthermore he recommended a 3.73 rear gear saying that it will perform like a 3.42 rear gear. He explained to me what I had previously misunderstood, that ring and pinion gears are designed with a 26" tire in mind and that for every 1.5" over that size its like losing a gear set. I'm not competent enough to determine if thats a big load of crap or if there's truth in that. I would be interested in your opinions though.

Much thanks,

Daniel

 

[tfeverfred]

Makes sense. I learned, from my first Bucket, that a lot of performance figures have to be recalculated, when it comes to light weight cars like ours.

 

[ellis8500]

I went to O'Reilly's and bought a "higher than stock" stall speed converter for the Ford 302 with AOD. Worked out fine. No hard pull at idle. I did this because as I read about stall speed and all the factors that have been mentioned in this post it became apparent that there is no definitive way to determine a "correct" value for these cars. Besides, stall speed is a relative number dependent upon the total system. So forget all the analysis just get one that says it's 2,500 or so and you'll be good. Or if you have a Ford engine like you're supposed to in these Ford cars, just get one that's rated "Higher than stock".

 

[2old2fast]

If you have a clutch , you don't have worry about any of this !!!
dave

 

[fletcherson]

Nothing against ford engines, the olds idea is unique, I like it! Even ford uses GM parts, lol. (Just poking at ya, Bill)

 

[409T]

Hello all, I have an update.

I talked once again to the owner of of ACC Performance, Nelson, about his previous recommendation of his Boss Hog Bandit torque converter. He recommended a converter (47014)... he explained to me that the specs on the converter say that it stalls between 3600-4200rpm (those specs are for a vehicle weighing 3680lbs), but because of my weight it will stall between 1800-2000rpm and will fully flash between 2600-2800rpm. Furthermore he recommended a 3.73 rear gear saying that it will perform like a 3.42 rear gear. He explained to me what I had previously misunderstood, that ring and pinion gears are designed with a 26" tire in mind and that for every 1.5" over that size its like losing a gear set. I'm not competent enough to determine if thats a big load of crap or if there's truth in that. I would be interested in your opinions though.

Much thanks,

Daniel

I think you would be happy with that converter and the 3.73 gears. In the extreme, I have a friend who has been running 4.11 gears on 29" tires in his T-bucket for the last 25 years and he thinks it is just fine.

 

[Daniel]

Thanks for all the replies.

2old2fast, you're right, if it was a manual.....but my wife would kill me. I recently shelled out $6k convering my 442 to a six speed tremec. Lol

Thanks all.

Now on to my next question...... exhaust.

-Daniel

 

[Gary49]

Boy am I glad I read this thread! I have an LS1 with a 4L60E in my T and I thought my rear brakes weren't working. Then I thought my torque converter lock-up solenoid was stuck in the locked position, even though I wasn't getting any fault codes, but now I realize it must be the stock converter in the light car. What a relief.

 

[Spanky]

I'm using a "1900-2100" stall speed unit in my mildly modified 350 Chevy powered T and it works just fine. No stomping on the brakes at red lights or anything, and very quick off the line.

 

[PotvinGuy]

Anybody have a converter that works for them with a similar setup... a TH400 mated with a torquey motor in a bucket???

My bucket has a crate SBC with a TH400, and I use a B&M Holeshot (2600 stall) converter. Been doing fine for 20 years. Motor torque is only a factor if you have a monster motor idling at 2000 rpm. For us buckethead cruisers our motors make little torque at idle. So here's the deal for us: if you have to stand on the brakes hard to prevent moving, the stall is too low. Higher stall will make it easier to hold, but too high will be wasting power (and making heat) by slipping excessively. I think anything marked 2400-2800 should make you happy.

 

[Indycars]

I'm using TC rated at 2800 rpm. I definitely needed at transmission cooler. When running
70 mph, the temps would climb over 210°F when the TC was not locked up. Ideal temperature
is 175°F. Temperature needs to be measured where the fluid is the hottest and that is the
transmission output line to the cooler. Also around town it was a problem also.

The point I want to make is, plan on leaving room somewhere for a cooler if you need it. Better
to plan for it and not need it, then to not plan and need it.

 

[railroad]

FWIW, I am building a Cobra Kit and considered an auto trans. Under advise of the chief cook and bottle washer of the company, do not use less than a 3000 stall converter. I spoke to their main supplier for their auto equipped kits and he concurred.
The car has a similar weight of a T, about 2200 lbs. The tires will be 40 series on 18" wheels, so the tall tire issue will not be considered and accordingly no gear compensation. I doubted the 3000 stall, some what, but would rely on experience rather than a gamble.
Not sure if this helps, but I was almost in the same boat, decided to go 5 speed TKO 600.