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Discussion Starter · #1 ·
Hey everyone, I'm in the process of building the engine for my cobra and I was looking in to studding the crankshaft. I believe its something I can myself in my shop but i wanted to find out mainly how deep to drill the hole and how deep do u relief the hole for the threads or do u thread it the entire distance. has anyone else done this there self and if so how did u do it, lathe, mill, hand drill. I'm also going to cut it for 3/16 square key do I need to do one 180 deg from the original. with all that done do u do away with the press fit on the balancer and make it a slip fit. I was going to modify my lower pully support until i read that snots break from a torsional event and the pully support doesn't prevent that, and with the stud u really don't have a support. I called a couple of local automotive machine shops and they said the could doubled key the crank but they have never studded a snot before. So any help I can get from u guys will be much appreciated.
 

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Jimmy,

Check out the Terminator Table of Contents (TToC) at the top of this forum. Go to the Engine Section and go down to the Crank Tech I post and minimally read posts 1 & 3. Look at the pics. They will answer all your questions.

At the time I originally did this, the 9/16 ARP stud was a very good solution. Today I would use an ARP Gen IV LS7 Damper bolt, ARP part number 234-2504. It has an under head length of 5.185 inches and a shank diameter of 16mm (0.623") with a recommended torque of 235 ft/lbs using ARP UltraTorque according to ARP.

Ed
 

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For those who are reading this thread you should know that the crank snout studding technique was developed by none other than me in late 2010 to mitigate the snout breakage problem Terminator engines were experiencing. The technique requires the stud anchor point to go all the way back to the #1 main bearing. If it does not reach the #1 main bearing the breakage problem is, you guessed it, still a problem! I documented this modification in the ModFords 03/04 SVT Cobra TToC in 2011. I believe my fix development and documentation publishing substantially predates the Kinetic MotorSport crank snout modification.

The correct way to do this modification is in the TToC posts I have identified in post #2 above. The guys at Kinetic MotorSport have attempted to copy the technique using a fattened up multi diameter stud with 12mm threads and a larger center body with a factory drilled and tapped snout. This will not fix the problem and it will lighten your wallet by the $120 they are charging (at this time) for their modification.. The basic fastener replacement they promote indicates they do not understand either the dynamics of the snout failure problem or a workable fix for the problem. All they do is replace the OEM fastener with an ARP fastener. That is not the proper fix. The stud needs to be anchored in the #1 main not in the crank snout.

You will be both money and broken parts ahead in the game if you follow the fix documented in the ModFords 03/04 SVT Cobra TToC. You will continue to risk snout and massive engine failures if you use the Kinetic MotorSport fastener replacement that attempts to copy the original modification I developed in 2010 and documented for everyone to use in 2011. It is important to recognize that while the crank snout stud modification will prevent perhaps 99% of the broken snout failures it is still possible to break a studded snout if a sufficiently aggressive clutch is used. The best fix available at this time, is in the Crank Tech II write up in the Terminator Table of Contents (TToC). It involves increasing the diameter and length of the crank snout and is fully documented in the TToC post Crank Tech II.

While there are multiple ways to achieve the larger, longer snout of Crank Tech II the best way at this time is the construction of a billet crank using the new snout specifications. A word of caution about any modifications you make to your engines; whenever the source of the modification has copied their modification from someone or somewhere else you should be cautious. If it was necessary for them to copy, it means they do not understand the underlying dynamics of the physical phenomena they are attempting to control or modify — and you should be cautious about using an uninformed design / fix for the design challenge you are attempting to resolve in your engine.


Ed
 

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Discussion Starter · #5 ·
Hey Ed, I had read both your crank tech forums, and some other forums were u offered insight on this subject. In your drawing it looks like the the hole 15/32 hole is going into the #1 main cross hole. I it supposed to break in to that cross hole or stop just short of it, would that weaken the crank any if u do break into the cross hole. I also seen where u talked about increasing the press fit on the balancer in one forum but on another u mentioned to have it honed to a slip fit. Also is the 15/32 what u are drilling to before u tap it, none of my chart call for a tap drill that small for a thread tap or a form tap, what tap would u use with what class fit.

Thanks Jimmy
 

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Hey Ed, I had read both your crank tech forums, and some other forums were u offered insight on this subject. In your drawing it looks like the the hole 15/32 hole is going into the #1 main cross hole. I it supposed to break in to that cross hole or stop just short of it, would that weaken the crank any if u do break into the cross hole.
You can just come up to the edge of the #1 main cross drilling or you can go into the passage. If you just come up to it and the chip ever breaks off it will kill #1 main. If you drill through to #1 main but thread only down to the od of the oil passage w/o entering the oil passage you will have the best anchor for the stud. You will also have a nagging drip of oil at the snout of the crank. When you assemble the stud to the crank use some blue locktite to both lock the stud but also block oil from working its way between the threads and dripping off the front of the crank.

I also seen where u talked about increasing the press fit on the balancer in one forum but on another u mentioned to have it honed to a slip fit.
For a street application my preference is 0.0015" press fit and two 3/16" square, full length keyways 180˚ apart on the snout. Street engines do not get disassembled regularly like race engines do, so the press fit is not the same type of PITA as on the race engine. On the race engine the slip fit provides for easy maintenance. If you use a slip fit the keys need to be a hardened tool or spring steel not an as annealed key. The absolute best attachment is a splined snout and a splined damper hub but no one offers that today and it is pricey to do a one off.

Also is the 15/32 what u are drilling to before u tap it, none of my chart call for a tap drill that small for a thread tap or a form tap, what tap would u use with what class fit.

Thanks Jimmy
A tap drill chart will call for a 31/64 drill for a 9/16 x 12 NC thread. I went 1/64 smaller for an increase in the percentage of thread engagement using a cutting tap.

If I were studding a factory crank today I would give some thought to using an ARP Gen IV LS7 Damper bolt, ARP part number 234-2504 instead of the 9/16 stud. The stud diameter is 0.5625 and the 16mm LS7 damper bolt is 16mm (0.623) or about 0.060" larger in diameter. The big deal is not the larger diameter, the big deal is the ready availability. That said the 9/16 studs are readily available at ARP today and noticeably less expensive than the LS7 damper bolt.

Something to keep in mind about the OEM crank; The snout diameter is 1.25" and the press fit length is 0.700 inches. That amounts to 0.56 diameters of press fit. This is one of the reasons the dampers spin on the snout mucking everything up. When I did the billet crank I went to a 1.400" diameter snout and increased the snout length by 0.700" to provide for one full diameter of press fit on the new 1.400" snout. With a 0.0015" press fit the damper fits very tightly.


Ed
 

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Discussion Starter · #7 ·
Ok, thank u for all the help. I looked at the ARP-2504 part # and it pulls up gen III lS7 as well as gen IV lS7 damper bolt. Do u know if these are the same, I'm assuming so because of the same part #.

two 3/16" square, full length keyways 108˚ hart on the snout.
Was this supposed to be 180deg apart on the snout

I have have taps for a 9/16 thread but not the 16mm, I'm sure the LS7 damper bolt is stronger then 9/16 stud because of the increased diameter. Is 9/16 stub enough and the lS7 over kill, if really benefits the assembly I don't mind spending the money to get the what i need.

After the stud mod do u need the front support, or get one of the after market ones like from j2fab. On my previous build I was running all stock lower components manley pistons comp cam and springs, with a ported Eaton blower, 2.76 upper and the metco 2lb lower. This engine only had about 10,000 miles on it when I removed it to do this build. when I disassembled the engine I noticed the #1 main bearing had a good bit more wear on it than all the other bearings including the rods. I was using the Clevite 77 h series race bearing that were calico coated. The #1 had worn all the way through the coating. I was thinking the was caused from the stress on the crank from the blower without the front support. then I also thought this just might be normal when running all the modifications, The upgraded valve springs and increased lift and duration of the cams have to be a lot of increased stress on the front of the crank.
 

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Jimmy,

The correct ARP part number for the LS7 snout bolt is 234-2504. It is (according to their catalog) 5.185 long and uses a 16mm x 2.0 thread. Interestingly if you look at the ARP Catalog it spec's the bolt's UHL at 5.185". Other places on ARP website will spec it ~0.100" different — go figure? The big deal is the bolt is priced at $37 on the Summit site. The stud is about ⅓ that cost. Drilling and tapping the crank is the same either way — your call.

Front supports are a joke. They are the automotive equivalent of a sky hook. You need to remember they are held in place by four 8 x 1.25 metric fasteners — essentially 5/16 hardware. Years ago the blown alcohol crowd got their panties all in a wad over crank supports. In the end it made no difference. The snout of the crank is pretty robust in terms of bending moment. Four 5/16 fasteners on a Modmotor or four ⅜ fasteners on a Blown Hemi make exactly zero difference. Now that I have said that we should get some incoming about so-in-so says and had this experience. Bottom line don't waste your money. There are plenty of other much more needy items to spend money on.

Your bearing woes are because of the bearings you were using. Blown motors like soft metal not hard metal and not soft metal with a hard metal overlay. Use King Bearings and use either of their tried and true SI or HP series bearings (identical except for the oil holes and oil channel (HP is better but 2x the price). BTW which half of your bearing was showing the wear, upper or lower?


Ed

p.s. To put it into perspective, the load on the crank's main bearings from the valve springs, cam duration and lift is comparatively less than the load on an elephant's rear legs when a sparrow lands on its butt.

p.p.s In the oh by the way category this is what an OEM Terminator crank looks like with a stock length, 1.400 diameter snout;

Gas Composite material Engineering Fixture Machine


Look at the size of the snout and then look at the size of #1 main.

Here is a pic of the big and long snout on my Winberg billet;

Liquid Drinkware Cylinder Gas Bicycle part
 

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Discussion Starter · #9 ·
Sorry I can't believe I forgot to say that it was only the upper bearing showing the wear, there was none on the bearing in cap.

Are all the part #s still the same for the 9/16 stud nut and washer as what they are in ur Crank Tech post.

How did u increase the diameter of the snot on a stock crank. I sleeve bearing or bushing surface all the time, and normally u have a .004 to .005 interference fit and heat the sleeve red hot and drop it on and let it slow cool. Then finish turn to ur specs so the sleeve e is true to the shaft. I'm not sure how good this would work on a crank. If u used the right material and everything I don't see why it wouldn't work.

That billit crank is absolutely amazing. I've seen the CNC machines that they use to make a billit crank and it is a work of art. To think that someone designed and built a machine that can take a solid raw peice of steel and turn it into a crank with the oiling holes drilled is just mind blowing.
 

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Sorry I can't believe I forgot to say that it was only the upper bearing showing the wear, there was none on the bearing in cap.
OK that is what I suspected. Now think about this for a moment. I am not sure what size blower you have but lets say it's a 3.3L or smaller. That blower takes about 100 hp or less to drive. Lets say you have a middle of the road engine, power wise, i.e. 650 RWHP. 650 RWHP is about 764 FWHP (650/.85) which works out to 95 HP per front cylinder or 190 HP total. You blower is tugging upward with 100HP and your front two pistons are pushing downward with 195 HP. Who wins the tug of war, obviously the motor. However because you use a PD blower it always has XX lbs of boost so the tug on the crank is almost always the same and at low engine speeds the crank is going to have a greater tug upward from the blower than a push downward from the cylinders.

The wear you are seeing on the upper bearing insert is caused by the oil film being pinched off from time to time. The easiest fix for this is a step up in oil viscosity and the use of an oil additive called ProLong <=clickable. The higher viscosity will help sustain the hydrodynamic oil wedge and the ProLong will protect the crank and the bearings when or if the hydrodynamic wedge is breached.

Are all the part #s still the same for the 9/16 stud nut and washer as what they are in ur Crank Tech post.
Go to the TToC and go down to the Engine Build Threads section. The first post will be The Complete ModMotor ARP Fastener Listing. This is a downloadable PDF listing of all the ARP ModMotor fasteners, including the crank stud, nut and washer. The listing includes torque specs and stretch specs where appropriate. All part numbers are still good.

How did u increase the diameter of the snot on a stock crank. I sleeve bearing or bushing surface all the time, and normally u have a .004 to .005 interference fit and heat the sleeve red hot and drop it on and let it slow cool. Then finish turn to ur specs so the sleeve e is true to the shaft. I'm not sure how good this would work on a crank. If u used the right material and everything I don't see why it wouldn't work.
This is not easy. It requires the use of a submerged arc welding process and a very good crank shop. The guy who originally did it for me died. I have since found another crank shop in Denver that I think would do it equally well if they were asked. Their repair work is to die for. This is a pic of a journal repair they did for the PRI show three years ago. They intentionally destroyed both sides of this rod journal and then repaired one side to demonstrate their capabilities. The guys are absolute magicians!

Bumper Automotive wheel system Auto part Gas Automotive exterior


If I were going to have this work done today this is unquestionably where I would go. The name of the company is Mile High Crankshaft, located in (appropriately) Denver Colorado.


That billit crank is absolutely amazing. I've seen the CNC machines that they use to make a billit crank and it is a work of art. To think that someone designed and built a machine that can take a solid raw peice of steel and turn it into a crank with the oiling holes drilled is just mind blowing.
You are spot on Jimmy. Stunning falls short of the mark.


Ed
 

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Discussion Starter · #11 ·
That's great work, they can bring a crank back from the dead like that. With the new stud do I need to do double keyways or will making the original 3/16 and using a tool steel key be enough. I read on another forum that the double key way takes to much material off the snot of the stock crank.
 

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If your crank is a stock length 1.250" diameter snout you will need two keys. They not only need to be spring or tool steel, they should be hardened spring or tool steel 3/16 square and run the full length of the snout. Absent your ability to get the hardened spring or tool steel key stock the next best alternative is a hardened 8630 steel square key from ATI. The Keys are available through Summit and Jegs. The ATI part number is 916325. In Summit speak it is ATI-916325. In Jegs speak it is 085-916325. Be sure to use two keys 180˚ apart.

You should do your own research on crank snouts, crank snout failures, crank snout failure fixes and select the solution you like best. My personal preferred solution for my current build is a 1.400" diameter snout 0.700" long with a ⅝" diameter ARP 8740 stud anchored in #1 main and torqued to 285 ft/lbs of torque. Your preferences may be different and driven by ease of access, cost or strength considerations.

What you will decide is appropriate for your application will not necessarily turn out to be the same solution someone else might select — hence my admonition to select the solution you like best. The next time I do this (if there is a next time), I will design it with a Chrysler sized 1.531" snout diameter, 0.700 long using a splined snout and damper engagement. The crank uses a splined snout and the entire assembly (if it is RCD) looks like this;

Line Font Cylinder Automotive tire Parallel


The splined snout requires a new lower timing gear and blower drive hub that will need to get integrated into the harmonic damper. The snout bolt you will need to hold the whole mess together is a ¾ x 16 RCD bolt that is six inches long and anchors in #1 main (is this starting to sound familiar?)

Now if you use all commonly available existing RCD Chrysler hardware you can keep the cost down to several thousand dollars — but, and this is the big issue, it is virtually indestructible because it is designed for a much more abusive environment than we will be using it in.

BTW just because I do it does not mean you should do it or you can do it. Back to my original recommendation, "You should do your own research on crank snouts, crank snout failures, crank snout failure fixes and select the solution you like best."

You have gotten several fixes in the course of this thread some more robust than others and some more pricey than others. All you need to do is decide which is the better fit for your intended usage and budget and then go for it.


Ed
 
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