Eric,
Broken crank snouts are not caused by any of the things that Lethal talks about in that link. The thing that breaks crankshafts is an aggressive clutch, a big blower, and blower overdrive.
Here is how it all goes down. You take off your Eaton and put on a bigger aftermarket blower. Then, to handle the newfound torque from the new blower and other mods, you go to a new über clutch with all the extra beans necessary to handle your newfound torque, and of course, you use every trick in the book to prevent belt slippage.
After a few cautious shakedown passes, you are ready to see how much quicker all those dollars have made your ride. This time you spin the engine up to 6500 rpm, change gears, and the experience is nothing short of spiritual. After a few passes, you decide to step up your game and go to 7000 and then 7500 before shifting. 7500 feels so good you just keep using that shift point each outing.
When your crank spins 7500 rpm, for example, your blower will spin 22,000 rpm or more. Your T-56 has a 2.66 first gear and a 1.78 second gear. When you change gears, that instantly drops your engine speed 33%. It also produces a 33% drop in blower rotor pack speed. The rotor pack goes from 22,000 rpm to 14,700 rpm. When you reduce the rotor pack rpm by 7,300 rpm literally in a microsecond, it is the functional equivalent of spinning your flywheel, to 7,300 rpm, and instantly stopping it. This is a monstrous, instantaneous torque hit opposite to the normal direction of crank rotation. The rpm drop between other gears is similar but does decrease slightly with each subsequent gear change.
The guy who takes the brunt of all this is the wimpy 1.25” diameter snout Ford puts on our cranks. The absolute fix is a super steel billet crank with a 1.400” or 1.500” diameter snout and a 5/8” or ¾” stud in the snout of the crank. An alternative would be an RCD style spline drive on the 1.500” snout. Spline drives look like this;
![Cylinder Gas Microphone Scientific instrument Flag]()
This is what the ¾" x 16 tpi 6-inch long snout bolt that is used with those style snouts looks like. Sort of reminiscent of our own crank stud mod.
![Auto part Engineering Metal Titanium Steel]()
The diminutive 8mm fasteners that we have on the front of our blocks do not even begin to meet the minimum strength requirements to prevent a bending moment style of breakage. More significantly, the girdle that Lethal offers provides zero protection against torsionally induced fractures or breaks.
Far and away, the best, most cost-effective fix for our cranks is the 9/16” Crank Stud mod that I developed years ago. It will not prevent the breakage, but it will push it far enough out in time that you can catch the damage and replace the wounded crank over a winter engine freshening before it kills your engine.
The absolute fix is a billet crank with a 1.400” or 1.500” splined snout, like in the pictures above. That will set you back about $4,000 in today's dollars — ask me how I know. Then get ready for another $1,000 or so in custom damper fabrication.
Over the years, there have been multiple girdles offered by multiple providers. They appear for a while, everybody has great enthusiasm and high hopes, and then someone’s crank breaks! Girdles are like sky hooks. They are fanciful solutions to a problem they can not resolve.
More often than not, girdles are purchased by someone who doesn’t want to take the time and effort to remove his crank and have it drilled and tapped for a stud. The fanciful crank support will typically cost somewhere between $1,300 and $2,000 and is pursued because the individual is too lazy to pull his crank out to get it studded. Instead, he attempts to fix the problem by throwing money at it.
Don’t waste your money.
Broken crank snouts are not caused by any of the things that Lethal talks about in that link. The thing that breaks crankshafts is an aggressive clutch, a big blower, and blower overdrive.
Here is how it all goes down. You take off your Eaton and put on a bigger aftermarket blower. Then, to handle the newfound torque from the new blower and other mods, you go to a new über clutch with all the extra beans necessary to handle your newfound torque, and of course, you use every trick in the book to prevent belt slippage.
After a few cautious shakedown passes, you are ready to see how much quicker all those dollars have made your ride. This time you spin the engine up to 6500 rpm, change gears, and the experience is nothing short of spiritual. After a few passes, you decide to step up your game and go to 7000 and then 7500 before shifting. 7500 feels so good you just keep using that shift point each outing.
When your crank spins 7500 rpm, for example, your blower will spin 22,000 rpm or more. Your T-56 has a 2.66 first gear and a 1.78 second gear. When you change gears, that instantly drops your engine speed 33%. It also produces a 33% drop in blower rotor pack speed. The rotor pack goes from 22,000 rpm to 14,700 rpm. When you reduce the rotor pack rpm by 7,300 rpm literally in a microsecond, it is the functional equivalent of spinning your flywheel, to 7,300 rpm, and instantly stopping it. This is a monstrous, instantaneous torque hit opposite to the normal direction of crank rotation. The rpm drop between other gears is similar but does decrease slightly with each subsequent gear change.
The guy who takes the brunt of all this is the wimpy 1.25” diameter snout Ford puts on our cranks. The absolute fix is a super steel billet crank with a 1.400” or 1.500” diameter snout and a 5/8” or ¾” stud in the snout of the crank. An alternative would be an RCD style spline drive on the 1.500” snout. Spline drives look like this;
This is what the ¾" x 16 tpi 6-inch long snout bolt that is used with those style snouts looks like. Sort of reminiscent of our own crank stud mod.
The diminutive 8mm fasteners that we have on the front of our blocks do not even begin to meet the minimum strength requirements to prevent a bending moment style of breakage. More significantly, the girdle that Lethal offers provides zero protection against torsionally induced fractures or breaks.
Far and away, the best, most cost-effective fix for our cranks is the 9/16” Crank Stud mod that I developed years ago. It will not prevent the breakage, but it will push it far enough out in time that you can catch the damage and replace the wounded crank over a winter engine freshening before it kills your engine.
The absolute fix is a billet crank with a 1.400” or 1.500” splined snout, like in the pictures above. That will set you back about $4,000 in today's dollars — ask me how I know. Then get ready for another $1,000 or so in custom damper fabrication.
Over the years, there have been multiple girdles offered by multiple providers. They appear for a while, everybody has great enthusiasm and high hopes, and then someone’s crank breaks! Girdles are like sky hooks. They are fanciful solutions to a problem they can not resolve.
More often than not, girdles are purchased by someone who doesn’t want to take the time and effort to remove his crank and have it drilled and tapped for a stud. The fanciful crank support will typically cost somewhere between $1,300 and $2,000 and is pursued because the individual is too lazy to pull his crank out to get it studded. Instead, he attempts to fix the problem by throwing money at it.
Don’t waste your money.
