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5.0L (1979-1995) Mustang Technical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.

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Old 12-18-2006, 02:59 PM   #1
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Default Causes of a broken crank...

What would cause a crank to break? From what I have been told, the car was slowing down from highway speeds to a stop and simply died. The harmonic balancer cracked and upon removal of balancer, it simply fell apart. Upon teardown of motor, I found that the crank had broken behind the rods of piston 1 and 2 (front most pistons) at the counterweight on the crank. The bottoms of pistons had slight damage from the breakage but nothing else looks too bad. What are the possibilities that my block is fubarred? I had planned on getting a 347 kit anyways so I am just worried about the block at this point. Motor had over 135K miles (speedo cable is broken and that is where the odometer stopped). Cylinder walls look good and no scratches that I can feel. I planned on getting the block checked out at a machine shop anyways, but am looking for an estimate of how bad this could be. Im kinda bummed but want to make sure I am going into this and not be surprised about anything. I like this forum so far and have found lots of info - thanks!

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Old 12-18-2006, 03:16 PM   #2
mattdel
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Default RE: Causes of a broken crank...

high rpm's with low oil will do that every time. compression was probably a little higher in those cylinders than the others, or maybe just happened to be firing those cylinders when it died. with failure like that, most times the block is no good. have it checked out, you might get lucky.
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Old 12-18-2006, 03:18 PM   #3
frdmstng1986GT
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Default RE: Causes of a broken crank...

take your block to the machine shop to have it checked out. a crank can break because of many reasons but seing as how you said the harmonic balancer fell apart when you took it apart i would say that was your reason. if a harmonic balancer slips.. or isnt exactly in perfict working order it can case harmonic vibrations throughout the crank and causeing stress cracks and such and possabily causeing the crank to break over time. probably the balencer was bad to begin with. just my guess.
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Old 12-18-2006, 03:27 PM   #4
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Default RE: Causes of a broken crank...

OK, so lets say that the block is bad or "on the edge of bad". What is a good company for blocks? Prices (thats gonna be scary - I have way too good of taste lol)? I need to start researching so I can have all this figured out before I take it to the shop and checked. I need the answers to all the questions that my GF will ask. I am sure some of you know what Im talking about.
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Old 12-18-2006, 04:27 PM   #5
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Default RE: Causes of a broken crank...

Depending on what you want to do, junkyard blocks are cheap and you can have it rebuilt or whatever. I got a junkyard longblock for $150 granted I had to basically pull the engine... Shortblocks that are built and ready to go are *quickly glances through 5.0Mustang Mag* around 1500-2500 depending on what you wanna get, displacement, internals, etc.

These are a few:
DSSracing.com
coasthigh.com
texashotrods.com
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Old 12-18-2006, 04:42 PM   #6
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Default RE: Causes of a broken crank...


Quote:
ORIGINAL: Scout2232

Depending on what you want to do, junkyard blocks are cheap and you can have it rebuilt or whatever. I got a junkyard longblock for $150 granted I had to basically pull the engine... Shortblocks that are built and ready to go are *quickly glances through 5.0Mustang Mag* around 1500-2500 depending on what you wanna get, displacement, internals, etc.

These are a few:
DSSracing.com
coasthigh.com
texashotrods.com
i have heard alot of bad things about dss motors.
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Old 12-18-2006, 04:44 PM   #7
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Default RE: Causes of a broken crank...

for the price it would cost for a machine shop to check out your block you could buy a new one and save yourself money in case they say its no good. You can get a block for $50 bucks.
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Old 12-19-2006, 02:49 AM   #8
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Default RE: Causes of a broken crank...

If my block tests out no good, I will look into a 1994+ 351 block.
Considered that route?
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Old 12-19-2006, 02:52 AM   #9
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Default RE: Causes of a broken crank...

Cranks don't like cogged blowers. Trust me.
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Old 12-19-2006, 02:58 AM   #10
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Default RE: Causes of a broken crank...

if ya wanna go bigger with the block, i'd probably go with an aftermarket one anyway. or just get a crate motor.

looking in my muscle mustang magazine, i found www.coasthigh.com

they have built 347's like u wanted.

shortblock...2000-2600

dynotech longblock....5800

dart (very strong block) powerblocks...shortblock 4900 and up longblock 9400 and up
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Old 12-19-2006, 02:58 AM
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50, 50l, 94, ballancers, break, broken, crank, crankshaft, detonation, dssracing, gt, money, mustang, shaft, time

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