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By Barry L - 11 Years Ago
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Picked up a 312 crank cheap with this repair ...keyway piece welded back in place, timing gear slides on without the woodruff key in place, seems to go on too easily. Question is, would you trust this repair or is this a scrap crank?
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By Hoosier Hurricane - 11 Years Ago
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I would trust that repair on a mostly stock street engine. I would be more concerned about the loose fitting gear. How loose is it? Is the damper also loose? Someone may have taken a light cut on the snout and made the components too loo
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By Barry L - 11 Years Ago
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The timing gear slides on easily and without the woodruff key, it also will spin easily. With the TRW gear there is less play as it has only one keyway slot. The multi-keyway gear is noticeably looser with less "meat" touching the crank. The damper slides on with little effort as well. With the damper key installed the damper takes little effort to seat and can be pulled back off by hand. The crank gear with a key installed can still be wiggled back and forth ever so slightly. The crank snout measures 1.249 at the front and decreases to 1.2483 as best I can measure. I think the damper would be OK, but the gear wouldn't be good.. I'll take it to a shop and see if there is some repair that is affordable and will give the proper fit.
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By 2721955meteor - 11 Years Ago
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the crank is cast iron,welding cast iron is very trickey,it can work on cylender heads if heated to near melt and re machined, but on crankshafts,especialy that aria that is weak to start with. my opinion is take it to the scrap and save your self alot of trouble down the road.It looks like the damage was from a timing gear failure. the key way will neve last.with the damper loose that makes the the crank worth its weight as good cast at the junkyard.
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By Hoosier Hurricane - 11 Years Ago
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It probably isn't worth the cost, but the snout can be chrome plated and reground to size. There are also places that can metal spray a shaft to repair a worn or undersize condition. Does not create the heat that welding does. Electric motor repair shops use these two methods to save the rotors in large motors.
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By NoShortcuts - 11 Years Ago
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I like John's thoughts. Plating the snout and then finishing it to size sounds like a reasonable approach with no heat involved. The flame spraying technique is interesting, too. We had a Eutectic torch unit for metal spraying at work. Heat was involved to accomplish bonding, but it was not a fusion weld to the base metal piece. We used the technique for building up shafts while they were spun on a lathe. The surface was turned down afterwards to the appropriate diameter.
Another out-of-the-box idea that crosses my mind is knurling the undersize surface on a lathe and then turning the surface to the correct diameter. I'd use a diamond pattern knurling tool rather than a straight knurl. -The idea is the same as what was once common practice on piston skirts. SLIGHTLY increase the diameter for refitting purposes. While the diamond knurling tool would be used, the impression in the crank snout surface would only look like an 'X', not the pointy gripping surface we see on tools like some ratchets or drive punches. The material next to the 'X' impression is displaced, i.e., pushed out to increase the diameter slightly.
As was suggested, I suspect someone took a light finish type cut to clean-up the surface perhaps related to the welding of the damaged keyway. On a metal lathe, IF the tailstock is not properly aligned with the headstock, the turned surface of a shaft will have a slight taper, i.e. one end will measure different than the other. Another possibility might be that the end of the crank positioned in the chuck was not accurately centered.
312 cranks are getting tougher to come by... Personally, I'd try to save the crank.  |
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By Pete 55Tbird - 11 Years Ago
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Would it be possible to turn the damaged snout down undersized an put a sleeve into it? Pete
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By 2721955meteor - 11 Years Ago
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industrial chrome could work if not for the key situation,but to chrome you need to true up the crank grind it afew thou then chrome then grind again. when i worked we had bucket pins and shafts when gears when pressed on. the proses was not sucsesfull on cranks,most broke,tho that was diesel engines.i would think very pricey endever.
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By NoShortcuts - 11 Years Ago
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Back-in-the-day, late '60s... early '70s before they closed, Crankshaft Company in CA used to offer hard chroming of crankshafts...
Gosh. That was a while ago! 
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By NoShortcuts - 11 Years Ago
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Barry L (8/12/2014)
...The damper slides on with little effort. With the damper key installed the damper takes little effort to seat and can be pulled back off by hand. The crank gear with a key installed can still be wiggled back and forth ever so slightly. The crank snout measures 1.249 at the front and decreases to 1.2483 as best I can measure.
Per John Mummert's web site @ http://www.ford-y-block.com/crankshaftid.htm, the crank snout is supposed to be 1.250! You're not 'off ' very much even if your mic calibration isn't spot on.
I'd pursue the notion of knurling the slightly undersize surface. Pushing a minimal 'X' pattern into the surface will grow the diameter AMAZINGLY well! With so little to be 'added' to the diameter, final fitting of the timing gear and damper may best be accomplished using just a long angle lathe file to smooth the knurled surface slightly afterwards and make the necessary 'fit' adjustment.
Let us know how you make out...
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By ian57tbird - 11 Years Ago
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Loctite has some fantastic products that might be suitable.
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By NoShortcuts - 11 Years Ago
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More thoughts on knurling the snout of the crank to adjust the fit of the timing gear and damper...
Because of the keyway for the timing gear, that area of the crank snout might best be done with perhaps three separate knurl bands... - Each band would start and stop on either side of the keyway opening... the operation would be done with the spindle turned by hand, not with the lathe power on... The crank would be rotated first in one direction and then in the other while the knurling tool is pressing against the snout surface. - After going first in one direction to the keyway opening and then back to the other side of the keyway opening, the knurling tool pressure against the surface would be increased by turning the cross-slide hand feed wheel. - With the small amount of material that needs to be displaced (raised) to accomplish the desired 'fit', I would expect that two depth adjustments of the knurling wheels against the crank snout surface for each individual band would suffice. ___________________________ For the area where the front damper rests when installed, knurling done on either side of the keyway area may be all that is necessary. IF this is the case, the usual process of making a continuous knurl with the lathe spindle under power and the lathe carriage driven by automatic feed may suffice. IF the knurl needs to be in a limited area for the damper unit, and the keyway is part of that, the same procedure used for the timing gear can be employed. ___________________________ What I've described may sound difficult for someone not familiar with metal lathe operation or the knurling process. A machine shop (not necessarily an automotive machine shop) will execute this fit adjustment of the sprocket and damper easily. -They will not look at you like you've got two heads when you request the work.
Hope this helps. |
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By charliemccraney - 11 Years Ago
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I think Jerry Christensen wrote in an article in Y block Magazine that he machines his dampers so they're not real loose but slip on by hand. Does anyone else remember that?
Further, aren't the damper, slinger, and timing gear longer than the crank snout? Once that bolt is tightened, it is all clamped in place and isn't going anywhere.
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By 2721955meteor - 11 Years Ago
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why risk all the resulting damage when this venture will fail,the reason the dampner is pressed on is it excepts the harmonic vibes, so the crank wont break,along with driveing the acesoryes.the timeing gear and chain requier lots of power,and vibrations as a resultof opening and closing of vave train. interesting coments,but put the crank up on the shop wall, or interduce it to the scrap dealer
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By Barry L - 11 Years Ago
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Thanks everyone for the input and ideas, but I've decided against trying to fix this iffy repair. I know I would never really trust it and should it fail, there would be too much carnage elsewhere. Coming soon...a new wall ornament. I can use it to explain to guys what to look for when trying to distinguish 292 from 312 cranks. It'll go next to the rod and piston labelled " it was runnin' when we parked it"
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By Y block Billy - 11 Years Ago
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I read somewhere that if you go around the area with a prick punch it raises the surface to do similar as knurling and I have done it before with success and also used lock tight with the install. However, your crank being welded on is another story to take into consideration. A loose cam gear will make it sound like you have a knock in your engine thats hard to diagnose, had a 4 cylinder boat motor that had that delema once.
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By NoShortcuts - 11 Years Ago
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2721955meteor (8/15/2014)
why risk all the resulting damage when this venture will fail,the reason the dampner is pressed on is it excepts the harmonic vibes, so the crank wont break,along with driveing the acesoryes.the timeing gear and chain requier lots of power,and vibrations as a resultof opening and closing of vave train. interesting coments,but put the crank up on the shop wall, or interduce it to the scrap dealer
Cliff, you're right! I can't imagine the calamity that took place that generated the force to displace the timing gear woodruff key in the snout of that crank. There's no real way to tell the underlying condition of the metal in that cast crank.
I've got a 312 crank kicking around that I THOUGHT about trying to have repaired. It has one throw that is badly beaten up AND blue from being run. I'd guess that the engine continued to be operated after the rod started knocking. Being an iron casting, welding is a gamble even with the proper preheat.
Some things are best relegated to being 'conversation pieces, only'...  |
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By CK - 11 Years Ago
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What about cutting a key way on the other side of the crank?
Then remark the crank gear with the according tooth to time.
I also agree with Charlie, as the balancer will press and hold the gear against the shoulder.
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