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Repairing a Rod Journal on a Callies Aftermarket Forging
By Paul Savadin
During more than 30 years in my small but comfortable shop, I have repaired thousands of crankshafts by welding. One thing I have learned in that time is that when a customer brings a crank to be repaired, you must take note of exactly what type of crankshaft you will be working on.
Many of the aftermarket cranks being used today are very different than the original stock crankshaft. The aftermarket crankshafts are usually made of much better grades of steel, so it is not uncommon to have two cranks that look exactly alike.
But if one is a 5140 grade of steel and the other is a 4340 grade, the price of the 4340 crank may be as much as $200 higher just because of the quality of the steel. Knowing the difference is critical – for example, I would not want you to weld on my 4340 crankshaft with mild steel rod.
Another thing that is critical is the radius on both sides of the journal. Most small block Chevy cranks use a .125˝ radius. On most aftermarket cranks or racing cranks it is very obvious that the radius is much larger than on the stock unit. Why? The larger the radius, the more strength the crankshaft will have and so the more durable it will be. For this reason, successful racers look for shops that specialize in high performance work and are familiar with this type of technology.
Many an unsuspecting racer has taken his shaft to be ground at a general automotive type of shop and ended up with all the radius cut out of it. Most shops with a good reputation do not mind answering customer questions. The ones that do not want to talk or explain anything are the ones customers should stay away from.
Does the crankshaft have to be nitrided to get it back to a 50 Rockwell hardness? Not always. The rule here is to consider what the crank will be used for…what is the application? Certainly, if it’s to be used in a Top Fuel car, then it needs the works. But for a street-driven street rod type of application, a stock crank with a good grind and polish will work great. If you take it to the track and stand on it weekly, it should be hardened or nitrided.
I have found that it never hurts to build anything “over-kill,” as long as you have the funds. My 18-year-old son P.J. has a 1967 Chevy truck. It is set on a 1980 model Chevy station-wagon frame and is lowered. It has a 377 small block Chevy with H-beam rods and a Scat 377 nitrided 3.480˝ stroke crank fit in a 400 block. It could be said the H-beam rods were not a must, and surely we could have gone with a less expensive crank. Like I said, it is all in what your customers can afford. Your customers all want something as nice and as cool as their funds allow.
During racing season I get many small block Chevy cranks of all types to repair. Most of the time the damage is only on one rod and the rest of the crank is perfect, so we work on making that bad journal as good as the others on the shaft. We do not pre-grind the bad journal unless it is all jagged or looks real bad. Most of the time they are smooth and just discolored.
After the crank has been cleaned so it is free of oil I place it on the V-blocks on my welding bench. I take a reading with my dial-gauge to see just how much the crank is bent. The journal on the Callies small-block Chevy crank featured in this article is damaged on the rear rod journal. This is the easiest to repair, as the closer the journal is to the outside the less it will bend from welding. If the crank is bent I always like to straighten it back to zero where everything is running true. It also gives me an indication of how easy it will move when I straighten it after welding.
I use a Miller Gold Star TIG machine, also known as a Heli-Arc machine, to do all my repair work. I used to use my Linde MIG welder, but it is much easier to do the repair with the TIG. The only time I use the MIG is for the few welded strokers that I still do.
It should be noted that I use only straight Argon gas on my TIG machine. I have experimented with tri-mix gases, but found out that while they are very good to weld aluminum, for steel, straight Argon will do the job, and is about half the price of a tri-mix gas.
To begin welding I lay the crank in the V-blocks on my welding bench with the snout to the left and the rear seal to the right, as I face the crank. I always weld the top half of the rod journal first, then, after letting the crank cool for five minutes, weld the bottom half.
I discovered years ago that by welding the top half of the journal first it is much easier to keep the crank straight and have less bend to straighten.
Because most of the bending comes when you weld on the bottom of the crank in the radius, by welding the top first it pulls the journal upwards, greatly minimizing the amount the crank will bend. I have done repair jobs on stock 350 small block Chevy cranks using this procedure. When both top and bottom halves of the journal were welded the shaft was straight to within .001˝. Usually journals on the end, which would be number one or number four journals, will bend about .020˝. The center journals, number two and number three, can bend as much as .060˝.
I begin the weld on the left side of the journal. I rotate the crank to where the oil hole is almost straight up towards me and begin my first pass of weld about an inch below the oil hole, which is the bottom of the top half of the journal. Start in the left radius and follow the radius all the way across the top of the journal and down the other side to where the pass of weld is half way around the journal.
Now go back to your starting position and do the same thing on the right side of the journal. Start even with the weld on the left, but now you are welding the right side of the radius. Once you have completed the weld on the right, place a second bead of weld right next to the one you just welded. This will widen your weld. Then place a second bead of weld on the left side.
After welding two beads of weld half way around the crank on both the right and left side go back to where you began your first weld. Now weld from side-to-side filling between the two beads on the right and left.
Be generous in the amount of weld you lay on. It is always better to have too much than to get to .030˝ above standard size and have to do a bunch of patching on low spots. Weld from side-to-side filling across the top of the journal and down the other side. When the weld is completed allow five minutes to cool.
Now it is time to weld the bottom half of the journal. Start on the right side and run a bead of weld from the center of the bottom of the journal to the spot where you finished your previous weld. Then run another bead next to it. Next run two beads on the left side. Now fill in by welding side-to-side.
When you have completed this you may now weld the final quarter of the journal. Weld two beads of weld in the right radius, then two beads in the left radius and fill by welding from side-to-side. Your journal weld is now complete.
It is very important to do your straightening while the crank is hot. So as soon as you finish that last weld be ready to hammer and chisel to get your crank straight.
Yes, even in a high technology world, I prefer a hammer and chisel. In my humble opinion every straightening press should be scrapped. Besides, why buy a press when all you need is a hammer and chisel?
The straightening process requires a straightening table made of heavy steel plate with two V-blocks. The Vs on the V-blocks should be coated with brass to keep from scratching the good journals on the crank.
All pressing a shaft to get it straight does is fracture it internally. The crank has a pretty good chance of failure too. Also, a shaft that is pressed to straighten will not stay straight. It will relieve stress and bend after it is installed and, again, cause engine failure. Yes folks, that is why some of you scratch your heads over those unexplained engine failures, so, in my opinion, under no circumstances should a crankshaft ever be pressed.
To straighten the just-welded shaft by peening with a hammer and chisel, place a dial-indicator on the number four main and rotate the shaft to get a reading. Go to the lowest reading. This will be in the bottom of the journal. The chisel that you use should be rounded and polished to about an eighth-inch radius. This will minimize the dings put in the weld.
Strike the journal in the bottom with the hammer and chisel. Give it three to four good hard raps on both sides of the radius. Rotate the shaft and take a reading with the indicator. It should be bent less each time you hit it. Always hit it in the low position. After a few raps the crank will be straight enough to rough grind.
The ideal situation is to knock the journal where it is about .003˝ to .005˝ over center, as the journal will relieve when metal is ground off of it. Grind the journal to within .020˝ of standard size then place it back in the V-blocks and check it for straightness again. If it is off a few thousandths go to the low spot and hit it again to straighten it. You will put marks in the radius where you hit it to straighten it, but they will be removed when you grind off the final .020˝ of material and go to standard size.
It should be noted that straightening a crankshaft, welded or otherwise, by peening with a hammer and chisel on V-blocks is an art. It must be practiced, and the more a person does it the better he or she will get. I have told many people how to straighten cranks by peening and have not had one person yet who was not happy with the results or who said that he could not do it.
Be sure to redress your wheel before removing the final .020˝ of material so you get a super smooth finish. It is best to grind off .010˝ of the remaining .020˝ in case a pinhole in the weld or some imperfection should show up. That way you still have some material left before reaching finished size to do any correcting if needed. If no imperfections show up at .010˝, then proceed onward to the finished size.
Once the journal reaches finished size, place the shaft in the V-blocks one more time for a final check for straightness. The shaft may be straight or may be out as little as .003˝ or less. If it is off, rotate the crank to the minus position on the indicator and, using a polished chisel that matches the radius, give a rap in that low spot and it will come right out.
You may not have to hit the bottom of your freshly welded journal to get the shaft straight, as often the low spot will line up to where you have to hit the main radius. In either case, a light rap with your hammer and chisel will get the indicator to zero.
As proof of the value of this method of straightening cranks, I have a true experience to relate. A Top Fuel racer from Indiana was staying at J.E. Kristek’s shop in San Antonio, TX, several years ago to compete in the A.H.R.A. Nationals being held there. He had installed a brand new crank several races earlier, but the bearings looked terrible on the mains ever since. J.E. told him to have me check the crank for straightness. As J.E. had guessed, it was bent. When the racer got back to Kristek’s shop with the newly straightened shaft, he placed it in his block. J.E. told me that he noticed the racer rotating and indicating the crank many times and that he was becoming irritated. When J.E. asked him what was wrong, the racer said that the indicator must be broken because he could not get any reading at all. Kristek only laughed and told him there was nothing wrong with the indicator – the crank was so straight it would not read. The racer raced the nationals and told me that was the best his main bearings had ever looked.
So this is how I repair all the race cranks that come through my shop. The procedure is the same on a 426, 454, 350 or whatever. It has worked for me for 31 years with no comebacks at all. If the same cranks do come back, it may have another journal damaged, but it is rarely the one that I repaired.
I use the TIG welder exclusively to do repairs and I use 1/16˝ 308 or 309 stainless rod. With the stainless rod you can weld right over nitride and never get a pinhole. It truly makes a great weld and has about a 60 Rockwell hardness. The stainless also holds oil well in its molecular makeup.
Anyone who has a little TIG welding experience, or is willing to gain some by practice, should be able to make crankshaft repairs of this type, but be prepared to work at doing it well. Crank grinding is an art, and like artists there are good ones, bad ones and great ones. It seems that crank grinders all have work, but the good and the great ones have a bunch more and always stay busy.