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#1
03-23-2014, 01:55 AM
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428 Crank Broke
Well I got around to tearing into my 428 after last falls failure.
This is what we found as we pulled the engine. 2 bolts gone on the pulley balancer end. The damage inside I found was a crank broke . All bearings Mains and rods looked nice and Silver. There is some minor Angel hair like gauling around on of the main caps. the bearing on Main # 2 spun a 180 . When I cut the filter aprt and inspected Nothing Bad ...looked just normal for the miles. I clean and strip down block inspect ......any cracks ? certain spots I should check ? To Repair ? New Crank Forged ......Yes. All new bearings mains and rods. gaskets and seals. Rebalance . Anything else to add to or check for ? Any and all advice is Welcome  .
__________________
 http://www.youtube.com/watch?v=DtKk5GNtWH0 Life is tough. Life is tougher when you're stupid. -John Wayne 
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#2
03-23-2014, 07:08 AM
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Check #1&2 Rods for straightness, free movement of rod-piston pin swing.
Mag block Mains 1&2. |
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#3
03-23-2014, 07:23 AM
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Glad you caught it before it could do any more damage.
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Carburetor building & modification services Servicing the Pontiac community over 25 years |
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#4
03-23-2014, 07:34 AM
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If the #2 main bearing spun the main bore needs to be align bored to clean that up.
Also could you post a picture of the bearings, they should not be silver, if all is well most of the dark gray break in coating should still be seen!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#5
03-23-2014, 11:10 AM
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Had a 455 crank break in the same location years ago. Stock balancer had a crack in the hub @ the key way. I'm guessing but I suppose the crack came from running up the rpm's much too high for a stock balancer. If it's a stock type balancer check the hub for cracks. Larry
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#6
03-23-2014, 11:45 AM
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ive got a 400 that looks like that.
all the old timers said it was a bad balancer that caused it on mine
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67 gto 400/400/3.90(sold) 69 lemans vert 400/400/2.78 89 trans am 350/700r/3.27 67 lemans custom |
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#7
03-23-2014, 11:51 AM
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It doesn't necessarily take high RPMs to break crankshafts. Bad balancers will break cranks quickly. The 6.5 Detroit Diesel turbo diesel is redlined at 3500 and will break their cranks under that RPM with bad balancers. Many sitting in scrap yards with broken cranks due to bad balancers at rather low RPMs. Once the rubber starts to deteriorate, your on borrowed time.
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Brad Yost 1973 T/A (SOLD) 2005 GTO 1984 Grand Prix 100% Pontiacs in my driveway!!! What's in your driveway? If you don't take some of the RACETRACK home with you, Ya got cheated    
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#8
03-23-2014, 12:15 PM
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Check your block very closely. When I had that problem it also cracked my block.
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#9
03-23-2014, 01:40 PM
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Quote:
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#10
03-23-2014, 02:04 PM
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This is exactly why balancers should be pressed onto the crank snout, NOT a slip fit as Pontiac did. Some aftermarket Pontiac balancers have a press fit now. Pontiac relies on bolt torque to hold the balancer tight on the crank, which is absolutely the wrong way to think on balancers.
Slip fit makes changing this stuff easy[which is why Pontiac designed it that way when they first designed these engines], but it's not the proper way to do it.
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Paul Carter Carter Cryogenics www.cartercryo.com 520-409-7236 Koerner Racing Engines You killed it, We build it! 520-294-5758 64 GTO, under re-construction, 412 CID, also under construction. 87 S-10 Pickup, 321,000 miles 99Monte Carlo, 293,000 miles 86 Bronco, 218,000 miles |
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#11
03-23-2014, 02:47 PM
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A Pontiac Balancer Bolt torque is something that should be checked a lot more than the average guy dreams about doing. Between the two piece design (early style) and the slip fit if anything is not right, a "loose" balancer will kill the crankshaft.
Some people on race type stuff will torque their crank hub bolt over 200 lbs/ft. Deal is the crank snout to hub inner diameter has to be correct. If the press is right then the keyway just helps index the hub to the crank. Sorry to hear about another crank issue. I am a fan of the ATI Balancers, Some like others. Tom Vaught
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
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#12
03-24-2014, 11:49 AM
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Quote:
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“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
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#13
03-24-2014, 12:27 PM
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I also wonder if you had the journals cut and if the radius was cut properly. That's exactly where a sharp cut radius will let go if the radius is too sharp, especially if not radiused at all.
Mark
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My Gasser '63 Catalina build. Oh sorry, it's a Street freak. Either way it's a fun build. |
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#14
03-24-2014, 10:48 PM
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Wow !!!
Thanx everyone. The balancer is a one peice Powerforce Bonded rubber. 5500-6000 miles is all on motor. It was COLD this onwe morning when I was staerting thwe Beast and I MAY HAVE got stupid with the throttle......... It will get a Block heater and a pan heat pad too. ShellRotella is NASTY OIL to work with too.....just like the Diesel crap at the Rig !!!! Now I need to get to Work and Gather parts and Stuff . Thanks All and everyone .
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http://www.youtube.com/watch?v=DtKk5GNtWH0 Life is tough. Life is tougher when you're stupid. -John Wayne
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