C6 bolt diameter for torque converter and stall recommendation

[73 SGM Mach]

How do I tell what type of c6 torque converter I have in my 73 Mach 1? There seems to be a 11 inch and a 11 7/16 bolt diameter. I am looking to put a larger stall converter in my factory c6. It was originally a 2 barrel 351c with c6 in it. I am looking at a B&M hole shot 2400-2600 rpm stall to replace the one I have. The motor is currently a 4 barrel car but I am looking to get more power in the lower rpms. Any help would be greatly appreciated!

https://www.cjponyparts.com/b-m-tor...1-7-16-inch-bolt-circle-c6-1967-1973/p/ATC28/

 

[73 SGM Mach]

I was doing some looking and finally found Don's spreadsheet on torque converter selection. The recommendation is in line with what I thought. Any other thoughts out there?
Jeff

 

[73 SGM Mach]

I went in and relooked at torque converters. B&m has a torque converter with 1900 to 2200 stall. Will this work a little better for the street? Also it says it fits a 1973 c6. Any help appreciated!
Jeff

https://www.jegs.com/i/B-M/130/40427/10002/-1

 

[secluff]

Hey Jeff,
The production-installed stock torque converter in your original '73 351C 2bl C6 is D1AZ-7902-A. My Ford specifications show a nominal size of 12" and a stall speed of 1,600-1,800 RPMs. This is the same torque converter that was in my parent's 400 C6 LTD and my '71 M code Mach1. It was great in my parent's LTD but was not worth a #@*!Ø& in my Mach1. I have posted in the past about how I tried to beat my Mach1 to death. I did what you could categorize as some very illegal out in the country, run what 'cha brung, no holds barred, ball$ to the wall drag racing. There was lots of racing, fighting, and money passing hands. I held my own and did pretty well, but you had to be a magician to get that car launched. There was a very small sweet spot in launching. Just under, it would leave like I was pulling a load of bricks and a little too much, and it would smoke the tires off the rims. I fixed that nonsense when I ordered a flywheel and torque converter like the one used in a '72 Q code Gran Torino I owned.
The Ford specs on this converter are 10 1/4 nominal diameter and a stall speed of 2,750-2,950. It made all the difference in the world. All I ever heard is how the 4bl Clevelands are pigs on the bottom end; the valves are too big, and they make good boat anchors (plus a few I'll leave out)! The same insults I'm sure others here have heard. But now....I could launch at a higher RPM where that sweet spot had been hiding and waiting to be unleashed, and I could let my "Too Big" valves work!

The specs on the converter you posted are close to the bottom numbers on the 351CJ-style torque converter. With the B&M converter, you should be able to use your existing flywheel. The Ford CJ converter from '71-74 was a smaller diameter and used a unique flywheel. The early versions had eight studs and were a PIA to remove. In May '72, Ford replaced the converter with a Gran Torino-sourced version with four studs.
To keep your car with good street manners, the torque converter is one of the easiest and most effective changes you can make to your transmission, and notice the difference in performance. It definitely made a difference in my "Boat Anchor, with the Too Big Valves"! That money was well spent, and I never looked back.

Please keep us posted on your decision and how it works out for you.

 

[73 SGM Mach]

Thanks for the too "BIG" valves i can really appreciate that as I have the same and I'm having the same issues. I have actually posted 2 converters.
1. 1900-2100 rpm
2. 2400-2600
But the 3rd is 2300-2500.
My concern is street drive ability. I do plan on drive ins and maybe some longer driving like a Route 66 highway cruise. I'm so undecided and really just don't know what to do.
Don's spreadsheet helped tons with not going to high but should I drop the rpm range if the longer drives are going to be what will be done mostly? But I still really want those Big valves to smoke someone off the line!

 

[Paul M]

Hey Jeff,
The production-installed stock torque converter in your original '73 351C 2bl C6 is D1AZ-7902-A. My Ford specifications show a nominal size of 12" and a stall speed of 1,600-1,800 RPMs. This is the same torque converter that was in my parent's 400 C6 LTD and my '71 M code Mach1. It was great in my parent's LTD but was not worth a #@*!Ø& in my Mach1. I have posted in the past about how I tried to beat my Mach1 to death. I did what you could categorize as some very illegal out in the country, run what 'cha brung, no holds barred, ball$ to the wall drag racing. There was lots of racing, fighting, and money passing hands. I held my own and did pretty well, but you had to be a magician to get that car launched. There was a very small sweet spot in launching. Just under, it would leave like I was pulling a load of bricks and a little too much, and it would smoke the tires off the rims. I fixed that nonsense when I ordered a flywheel and torque converter like the one used in a '72 Q code Gran Torino I owned.
The Ford specs on this converter are 10 1/4 nominal diameter and a stall speed of 2,750-2,950. It made all the difference in the world. All I ever heard is how the 4bl Clevelands are pigs on the bottom end; the valves are too big, and they make good boat anchors (plus a few I'll leave out)! The same insults I'm sure others here have heard. But now....I could launch at a higher RPM where that sweet spot had been hiding and waiting to be unleashed, and I could let my "Too Big" valves work!

The specs on the converter you posted are close to the bottom numbers on the 351CJ-style torque converter. With the B&M converter, you should be able to use your existing flywheel. The Ford CJ converter from '71-74 was a smaller diameter and used a unique flywheel. The early versions had eight studs and were a PIA to remove. In May '72, Ford replaced the converter with a Gran Torino-sourced version with four studs.
To keep your car with good street manners, the torque converter is one of the easiest and most effective changes you can make to your transmission, and notice the difference in performance. It definitely made a difference in my "Boat Anchor, with the Too Big Valves"! That money was well spent, and I never looked back.

Please keep us posted on your decision and how it works out for you

How do I tell what type of c6 torque converter I have in my 73 Mach 1? There seems to be a 11 inch and a 11 7/16 bolt diameter. I am looking to put a larger stall converter in my factory c6. It was originally a 2 barrel 351c with c6 in it. I am looking at a B&M hole shot 2400-2600 rpm stall to replace the one I have. The motor is currently a 4 barrel car but I am looking to get more power in the lower rpms. Any help would be greatly appreciated!

https://www.cjponyparts.com/b-m-tor...1-7-16-inch-bolt-circle-c6-1967-1973/p/ATC28/

W/a original 2b, you most likely have the larger 12" converter with the larger "common" bolt circle. It's the Q codes that had the smaller "odd" just under 9 1/2" bolt circle flywheel and 10 3/4" converter. I wouldn't etch that in stone, since A friend of mine has a few of these cars and we have seen the Ford factory mix and swap everything. Needless to say, the stock flywheels for the larger bolt circle converters are very flimsy. 1900-2100 will barely make a difference.

 

[Paul M]

Hey Jeff,
The production-installed stock torque converter in your original '73 351C 2bl C6 is D1AZ-7902-A. My Ford specifications show a nominal size of 12" and a stall speed of 1,600-1,800 RPMs. This is the same torque converter that was in my parent's 400 C6 LTD and my '71 M code Mach1. It was great in my parent's LTD but was not worth a #@*!Ø& in my Mach1. I have posted in the past about how I tried to beat my Mach1 to death. I did what you could categorize as some very illegal out in the country, run what 'cha brung, no holds barred, ball$ to the wall drag racing. There was lots of racing, fighting, and money passing hands. I held my own and did pretty well, but you had to be a magician to get that car launched. There was a very small sweet spot in launching. Just under, it would leave like I was pulling a load of bricks and a little too much, and it would smoke the tires off the rims. I fixed that nonsense when I ordered a flywheel and torque converter like the one used in a '72 Q code Gran Torino I owned.
The Ford specs on this converter are 10 1/4 nominal diameter and a stall speed of 2,750-2,950. It made all the difference in the world. All I ever heard is how the 4bl Clevelands are pigs on the bottom end; the valves are too big, and they make good boat anchors (plus a few I'll leave out)! The same insults I'm sure others here have heard. But now....I could launch at a higher RPM where that sweet spot had been hiding and waiting to be unleashed, and I could let my "Too Big" valves work!

The specs on the converter you posted are close to the bottom numbers on the 351CJ-style torque converter. With the B&M converter, you should be able to use your existing flywheel. The Ford CJ converter from '71-74 was a smaller diameter and used a unique flywheel. The early versions had eight studs and were a PIA to remove. In May '72, Ford replaced the converter with a Gran Torino-sourced version with four studs.
To keep your car with good street manners, the torque converter is one of the easiest and most effective changes you can make to your transmission, and notice the difference in performance. It definitely made a difference in my "Boat Anchor, with the Too Big Valves"! That money was well spent, and I never looked back.

Please keep us posted on your decision and how it works out for you.

yep the Cleveland 4V head (same as 70 boss 302 except slight water passage difference and slight chamber size) was designed for some kind of Can am racing. You'd have to crank it up to 8k to actually use them. It's not necessarily the valve size, as much as it is a mammoth intake port size. This is why 90% of the new aluminum heads have slightly smaller port sizes and valve sizes, they also want you to buy their intakes for them. Aside the point, without having a completely modified 351 w/stall n gears to accompany it, the problem was the dead air on the bottom of the port. Some used tongues on the bottom, others epoxy filled the floor up to 1/4" or you build a high RPM monster to fill the void. For my application the 4v heads are beasts. My buddy broke into the high 9's w cast iron Cleveland heads & swapped to aluminum & hardly noticed any difference in times. I'm talking he made upgrades to quite a few areas and he's still running w/in a few 10ths of the same times. Of course, he's running a stroked - alcohol injected Cleveland w/over 13:1 compression.

 

[73 SGM Mach]

yep the Cleveland 4V head (same as 70 boss 302 except slight water passage difference and slight chamber size) was designed for some kind of Can am racing. You'd have to crank it up to 8k to actually use them. It's not necessarily the valve size, as much as it is a mammoth intake port size. This is why 90% of the new aluminum heads have slightly smaller port sizes and valve sizes, they also want you to buy their intakes for them. Aside the point, without having a completely modified 351 w/stall n gears to accompany it, the problem was the dead air on the bottom of the port. Some used tongues on the bottom, others epoxy filled the floor up to 1/4" or you build a high RPM monster to fill the void. For my application the 4v heads are beasts. My buddy broke into the high 9's w cast iron Cleveland heads & swapped to aluminum & hardly noticed any difference in times. I'm talking he made upgrades to quite a few areas and he's still running w/in a few 10ths of the same times. Of course, he's running a stroked - alcohol injected Cleveland w/over 13:1 compression.

Wow! Thanks for the info. I was looking at changing the top end heads, cam, possibly manifold, but with what your saying I'm on the right path to start with the rear end change out and converter change. I have a new 3rd member already with trac-loc 3:50 gears. I'm getting anxious to get started!
Jeff

 

[Paul M]

Yep I'm right behind you on the rear end. The trac loc is the friction type. Nothing wrong with them as long as they aren't worn out. I'm kinda leaning tru track at the moment. That 3.50 gear ought to be nice.

 

[c9zx]

Paul, Your comments about your friends race car not going much faster when he switched from factory heads to aftermarket heads makes the point that the factory heads, from 1970, are pretty darned good. Making all the other parts work well with them is the key to good performance. And, you don't need to turn the engine to 8000 RPM to use the 4V heads effectively. You do need someone who really knows the 351C well to help with parts selection.
SGM, You need to decide what you want the most. Cruise at 2300 RPM on the highway, or better acceleration around town. I'd vote for around town smiles. Just my opinion. Chuck

 

[Paul M]

Paul, Your comments about your friend's race car not going much faster when he switched from factory heads to aftermarket heads makes the point that the factory heads, from 1970, are pretty darned good. Making all the other parts work well with them is the key to good performance. And, you don't need to turn the engine to 8000 RPM to use the 4V heads effectively. You do need someone who really knows the 351C well to help with parts selection.
SGM, You need to decide what you want the most. Cruise at 2300 RPM on the highway, or better acceleration around town. I'd vote for around town smiles. Just my opinion. Chuck

ye the 8k is a bit exaggerated. lmao The Q codes at least brought up the rpms a lil w the converters add a lil gear and these things rip. Most ordinary daily drivers don't need my opinion since I like over 3k on the converter 3:70 -3:91 for the gears. I had a 350 Chevy and had to go Dart pro1 to make hp, the Cleveland here w/ stock 4v heads not even 70 heads, built nicely is the stronger motor.

 

[73 SGM Mach]

Once I change the rearend and converter I am still leaning towards a bigger cam. Does anyone have recommendations? Attached is a picture of the cam specs. I have an edelbrock performer manifold, with a holley sniper set up and the 4v heads. I understand with a bigger cam I may need a bigger stall converter so I don't want to go to big. Thanks for the help on this.
Jeff

 

[Sheriff41]

I had a 268 cam in my car with a C6, 2800 stall, and 3.25 gears. It was a nice setup,though I would call the cam on the mild side. It did have a nice idle and created enough vacuum. Whatever cam you decide on get a pre-72 timing set since the 72 and later used a 4° retarded design.

 

[c9zx]

The low compression of the open chamber 4V engine is a problem if you want to install a meaningful more aggressive cam. The dynamic compression would suffer and it would exhibit poor idle quality, low manifold vacuum, and the lower RPM range would be soft. I think the static compression ratio is somewhere around 8.5:1. There is more to it than a new cam and lifters. New springs and pushrods would be needed (the stock pushrods are too thin walled for real performance work with modern cam profiles). The stock valves are a known catastrophic failure waiting to happen (the tops break off and the valve get pulled into the bore). I'm not trying to discourage you. I just want you to know what you are getting into. Also if the car was originally a Q code it should have the higher stall convertor.
On another note, you really shouldn't have 8 lines of coke in a photo you post on the internet.
I hope your project goes well. Chuck

 

[73 SGM Mach]

Lol!
Thanks Chuck!
Jeff

 

[Paul M]

There's nothing wrong with that cam, it should match the rpm range of the performer nicely. Note the 2 posts before me. Sheriff41 used a 2800 stall converter to accompany it. If your car was a base model not Q code it will most likely have the large 12" converter. You will not want to use it. At least you have the large common bolt circle that allows you to purchase a torque converter at a decent price. I also used the 4v open chambered heads, however, replaced the pistons w/ forged alum aftermarket ones to bump up the compression. (I also milled for my app which you don't have to mess with) Now back to Chucks statement. After you've bumped up the compression, you'll want to buy new pushrods, not stock since they are only 5/16, you'll want a performance pushrod. Get matching lifters & springs w/ the cam. I also don't like the stock valves for performance. Get new stainless w single groove keepers and have a reputable machinist do the valve job. If you have milage chances are your guides are showing wear. Do not waste your time to knurl, replace the guides. The crank and stock rods are fine with fresh machining. Oil pump, use a Melling hv with a hardened shaft. Everything gets balanced w/ your balancer & flywheel. Since it's a Cleveland and was only made a few years, don't be surprised to wait on some parts for weeks. Yes, to the 350 gear w/ this combo. 8 lines reminds me of the 80's lmao before mannitol & baby laxative took over.