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#641864 - Thu Apr 29 2010 11:51 AM Crankshaft Snout Drill & Tap Guide
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 11316
Loc: Dellrose, TN
Most of us who build stovebolt engines have experienced situations where the harmonic balancer has gotten loose and worn out the crankshaft snout, the Woodruff key, or both. In some extreme situations, the balancer comes off entirely and does a lot of sheet metal and/or radiator damage. While it's possible to recondition a damper with new rubber parts, once one is worn or damaged where it fits the crankshaft, there's not much it's good for but an anchor for a canoe! The 235 splash engine I'm rebuilding has this type of problem, with the crank snout worn about .002" under normal diameter. This will make the press fit of even a good-condition balancer pretty marginal.

Fortunately, there's a fix available- - - - -drill a hole in the crank snout and tap it for the same bolt & washer small-block V-8's used from the mid-1970's on, and keep the damper from loosening up and doing any damage. The trick is getting that hole drilled straight and true, and tapping it correctly. There's only one chance to do it right! The simplest, safest way is to set the crankshaft up in a drill press or Bridgeport mill during a rebuild, and be absolutely sure the hole is straight and true. How about the guy who wants to do the job in the frame, without dismantling the engine? The drill/tap operation is difficult at best, and disastrous in a worst-case scenario.

I am in the process of building a set of two guide bushings to slip over the crankshaft snout, one for the tap drill, the other for the tap, which will assure the hole, and the thread, will be centered and straight on the first attempt, even with the crankshaft in the engine, and if there's enough clearance for a 1/2" drill motor, with the engine in the frame. I've also got a balancer press that can bolt onto the crank snout once it's threaded, to install the balancer without hammering on it. Once I've case-hardened the guide bushings, I'll make the whole setup available for loan to forum members, with maybe a small deposit required just to assure they find their way home in a timely manner! Anybody interested?
Jerry
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My best friends are Sam, Eli, Bill, and Gene:
Samuel Colt
Eliphalet Remington
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#641872 - Thu Apr 29 2010 12:02 PM Re: Crankshaft Snout Drill & Tap Guide [Re: Hotrod Lincoln]
tclederman Offline
Registered: Tue Sep 18 2001 12:00 PM
Posts: 20807
Loc: Castleton-on-Hudson, NY

Jerry,

This is a very generous and helpful offer. When I did my last one, the engine was on the frame and the radiator was removed. I held my breath and hoped for the best, drilling by hand. Luckily, it turned out OK. I'd prefer not to take any chances.

A substantial deposit and a modest "rental fee" would be quite appropriate.

Thanks,
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#641878 - Thu Apr 29 2010 12:15 PM Re: Crankshaft Snout Drill & Tap Guide [Re: tclederman]
bigbadswingdaddy Offline
Shop Shark
Registered: Fri Dec 31 2004 12:00 PM
Posts: 2319
Loc: san francisco
or you can put a long gmc motor in there that has already been drilled. just messing. That is a very nice offer. that job would make my b-hole pucker every time without it.
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#641885 - Thu Apr 29 2010 12:45 PM Re: Crankshaft Snout Drill & Tap Guide [Re: bigbadswingdaddy]
Hookalatch Offline
Shop Shark
Registered: Tue Apr 14 2009 04:30 PM
Posts: 367
Loc: Cottonwood, CA
I had already drilled mine too. I would have been glad to pay a rental fee for the peace of mind. It made me a little nervous to do it freehand but it worked fine and drilled much easier than I expected. I think anyone who has used a proper tool (balancer press) to install dampers will agree that this sure beats pounding them on. I would be very hesitant to try to pull one on with just a bolt.

Chuck
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#641888 - Thu Apr 29 2010 01:00 PM Re: Crankshaft Snout Drill & Tap Guide [Re: Hookalatch]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 11316
Loc: Dellrose, TN
I've re-tapped several race car crankshafts to a bigger thread after someone stripped the original thread trying to pull a balancer on. The balancer press bolts on tight, and uses a 1" diameter fine thread to do the pressing. Much safer, especially if there's room for an impact wrench to zip it on quickly! Fortunately, a stripped 7/16-20 thread makes a hole almost big enough to accept the next larger size tap, a 1/2"-20! All it takes is a slight enlargement of the hole before re-tapping. BTW, the same drill-tap guide I'm building for the stovebolt engines will fit the early V-8 cranks, 265, 283, and early 327, that came without the center bolt.
Jerry
_________________________
My best friends are Sam, Eli, Bill, and Gene:
Samuel Colt
Eliphalet Remington
Bill Ruger
Eugene Stoner

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#641903 - Thu Apr 29 2010 03:24 PM Re: Crankshaft Snout Drill & Tap Guide [Re: Hotrod Lincoln]
Pete52 Offline
Shop Shark
Registered: Tue Jan 06 2009 10:40 AM
Posts: 1689
Loc: melrose pk. il.
When I rebuild my 235 this winter I'd rent it from you,or send in a deposit, Thanks.

Pete
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1952 Chevy 3100
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#641930 - Thu Apr 29 2010 05:11 PM Re: Crankshaft Snout Drill & Tap Guide [Re: Hotrod Lincoln]
OldSub Offline
Extreme Gabster
Registered: Sun Oct 05 2003 12:00 PM
Posts: 6663
Loc: Seattle, Washington
Originally Posted By Hotrod Lincoln
BTW, the same drill-tap guide I'm building for the stovebolt engines will fit the early V-8 cranks, 265, 283, and early 327, that came without the center bolt.

Last time I dealt with this problem it was on an early 327. I did it free hand and don't believe I got it straight.

However it worked a couple years afterward before spinning a rod bearing while a friend was driving the car well over 100 mph for some miles on the freeway. Until today I've never wondered if my drill work had anything to do with that failure.
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Its true, I really don't do anything but browse the Internet looking for trouble...
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'55 1st GMC Suburban . '54 GMC 250 trailer puller project. '54 GMC 250 Hydra-Matic . '54 Chevy 3100 . '47 Chevy COE . and more...
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#641980 - Thu Apr 29 2010 07:00 PM Re: Crankshaft Snout Drill & Tap Guide [Re: OldSub]
waldo53 Offline
Shop Shark
Registered: Sat Dec 09 2006 12:00 PM
Posts: 1707
Loc: ID
Well, the Stovebolt "help your buddy out" spirit is alive and well. That's a very generous offer Jerry, thank you. Don't need it now but ya never know. I too think a rental fee would be in order to recoup some of your time and effort.
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#642108 - Fri Apr 30 2010 02:50 AM Re: Crankshaft Snout Drill & Tap Guide [Re: waldo53]
blanch53 Offline
Wrench Fetcher
Registered: Fri Apr 17 2009 08:02 PM
Posts: 137
Loc: Vancouver Canada
This posting is very timely as I've just posted the question concerning the lack of a threaded bolt for the damper. I have my crank out of the block and want to get it polished, I'm considering having it drilled and tapped while in a lathe. What would be an appropriate size bolt 1/2 NF? Nice offer with the tool idea to be lent out.
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#642133 - Fri Apr 30 2010 07:54 AM Re: Crankshaft Snout Drill & Tap Guide [Re: blanch53]
Hotrod Lincoln Offline
Extreme Gabster
Registered: Mon Feb 23 2004 12:00 PM
Posts: 11316
Loc: Dellrose, TN
The standard bolt that's used with the V-8's is a 7/16 X 20, with a heavy flat washer. That's the simplest option, and it uses readily-available OEM parts. I have rethreaded a few to 1/2", but it's not my first choice. The lathe idea is a good one, IF you've got a big enough lathe, and you do something to protect the front main bearing journal when you set up the steady rest on it. A piece of oil-soaked leather wrapped around the journal might be a good option.
Jerry

_________________________
My best friends are Sam, Eli, Bill, and Gene:
Samuel Colt
Eliphalet Remington
Bill Ruger
Eugene Stoner

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