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post #1 of 27 (permalink) Old 07-05-2008, 08:28 PM Thread Starter
 
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Snapped Crankshaft

Guys just bought a immaculate 90 5 spd sc. When I tore into it I found out this car had a reman'e Ford engine installed in it. This car does not have one part on it that isn't ford. Hell even the PCV valves are ford. Anyways, I pulled the motor and found the crank was snapped right after the number 1 and 4 rod journals. I was just curious if this was common. I have another motor I am going to throw in it for right now but this motor is to clean to not rebuild. Open to suggestion on a crank. Also who knows wha they are doing on valve jobs for heads as well as porting them and matching the intake plenum to them. Was going to have the blower reman'ed with some slight mods to flow better. I am not looking to soup it up where it breaks every time I start it just want it to flow better. Was going to put SCP downtubes and exhaust as well as cold air intake and MAF and bigger TB. Appreciate any help and response. Look forward to getting this bird on the road it is really to nice to prt out. Thanks for reading,

John
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post #2 of 27 (permalink) Old 07-05-2008, 08:44 PM
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might be better to post this on sccoa if you can, they would probably answer faster and have a larger base for this thing...but im sure someone will know on here as well, just less scers view it as far as I can tell.
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post #3 of 27 (permalink) Old 07-05-2008, 09:51 PM
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i have 2 90 s/c's and yes its not an uncommon problem.... it does happen

typically the harmonic balancer starts wobbling and after going so long it snaps the crank

good luck finding another crank, there not that easy to source these days, you may have to go aftermarket with a different bore and stroke it.

no need for a new throttle body, the stock tb's can get you in the 12s

do a simple port job on the heads yourself, and the intake, a few hours with a hand grinder can do alot, port that blower too, no need to take it somewhere you can do it yourself just be patient and don't rush. also don't try to stay up till the wee-hours of the night to finish it that causes accidents to happen

ask me how i know?

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post #4 of 27 (permalink) Old 07-07-2008, 09:56 PM Thread Starter
 
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Thanks for the input guys
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post #5 of 27 (permalink) Old 07-07-2008, 11:29 PM
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And do not port anything of the exhaust side.

You can cleanup the intake and intake ports.

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post #6 of 27 (permalink) Old 10-21-2008, 09:12 PM
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Quote:
Originally Posted by decipha View Post

typically the harmonic balancer starts wobbling and after going so long it snaps the crank
What causes this?

Just picked up a car (94 Cougar V6) that vibrates horribly and I can see the crank pulley moving. A shop diagnosed it as having a bent crank and/or a bad pulley. First thing I'll try is putting a pulley from another 3.8 on it, but any heads up before that would be excellent!
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post #7 of 27 (permalink) Old 10-21-2008, 09:57 PM
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Quote:
Originally Posted by Faster7 View Post
What causes this?

Just picked up a car (94 Cougar V6) that vibrates horribly and I can see the crank pulley moving. A shop diagnosed it as having a bent crank and/or a bad pulley. First thing I'll try is putting a pulley from another 3.8 on it, but any heads up before that would be excellent!
If the crank pulley is wobbling, check the center bolt and see if it's even there. Usually it'll snap the head off. Anyways, the rubber core of the harmonic balancer fails, which causes excess vibrations, etc etc.

Anyways, the best way around it is to buy a new BHJ unit from SCP. DO NOT reuse a stock harmonic balancer. Very few people have had any luck with doing that. They all fail sooner or later.

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post #8 of 27 (permalink) Old 10-21-2008, 10:17 PM
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Quote:
Originally Posted by 95XR7 View Post
If the crank pulley is wobbling, check the center bolt and see if it's even there. Usually it'll snap the head off. Anyways, the rubber core of the harmonic balancer fails, which causes excess vibrations, etc etc.

Anyways, the best way around it is to buy a new BHJ unit from SCP. DO NOT reuse a stock harmonic balancer. Very few people have had any luck with doing that. They all fail sooner or later.
Right on. Between a friend and I, we probably have 800k combined miles on our 3.8 cars without any issues with the balancer (bolts, yes) and hadn't seen this! ~$400 for an aftermarket balancer for a $200 car, I'm not so certain about yet. $125 for the new dorman, or $10 for the sleeve I may think about. Sure it would have been a $1500+ car if it didn't "need a crankshaft"


Is there any actual balance built into the damper/pulley? Like one would find on an "externally balanced" V8 like a Chevy 400 small block or 454 big block.

Thanks!
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post #9 of 27 (permalink) Old 10-22-2008, 12:13 AM
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that happened to my uncles tahoe going up a mountain pass with a boat and trailer and over loading it the harmonic balancer wobbled and snapped the crank shaft right before the first bearing then a rod got thrown and ruined the entire block.

my other ride is an ambulance!
1997 V8 sport - first car - sold 6/7/10
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post #10 of 27 (permalink) Old 10-22-2008, 03:58 AM
 
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I love to look at carnaige? like that. When I went to pick up my friends block from a shop i noticed a pile of metal in the corner. Long story short, some Dumb AZZ ran someone elses built 442 for 10 min at WOT with no oil. words can't decribe how mangled it was. took four trips to find out what car it was in, and the name of the interior shop that F'ed up big time.
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post #11 of 27 (permalink) Old 10-22-2008, 10:09 AM
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Finding another crank really isn't too hard. A lot of guys on sccoa have several spare engines from aprts cars and would be willing to sell one.

If the crank pulley is wobbling, your balancer needs replaced. Replace it and KNOW you fixed the problem. Buying a Dorman balancer will do just fine. No need to go and spend $400 on a balancer.

-Thomas

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post #12 of 27 (permalink) Old 10-22-2008, 11:54 PM
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Quote:
Originally Posted by Thomas View Post
Finding another crank really isn't too hard. A lot of guys on sccoa have several spare engines from aprts cars and would be willing to sell one.

If the crank pulley is wobbling, your balancer needs replaced. Replace it and KNOW you fixed the problem. Buying a Dorman balancer will do just fine. No need to go and spend $400 on a balancer.

-Thomas
im surprised that you could do this sually when ever i buy cheaper stuff i get screwed over x 2. i mean every time too. i would think that you could do this with a balancer

my other ride is an ambulance!
1997 V8 sport - first car - sold 6/7/10
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post #13 of 27 (permalink) Old 10-23-2008, 08:04 AM
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I wouldn't use a used balancer because the rubber can dry rot. Sometimes they're cracked from setting the engine down on it too. Just not worth it for the peace of mind.
-Thomas

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post #14 of 27 (permalink) Old 10-24-2008, 04:37 PM
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Used BHJ balancer with steel inner hub...is okay to reuse. OEM balancer with aluminum inner hub...not okay to reuse. The aluminum hub is the biggest problem with the stock balancer.

David

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post #15 of 27 (permalink) Old 10-25-2008, 12:37 AM
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Snapped cranks suck. That's what killed my SC-- except, the black guy who had it before me put a N/A bottom end in mine.

-Ghost

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post #16 of 27 (permalink) Old 10-25-2008, 02:11 PM
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wow that blows

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post #17 of 27 (permalink) Old 10-26-2008, 07:53 PM
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Thumbs down That is sucky

Quote:
Originally Posted by The_Ghost View Post
Snapped cranks suck. That's what killed my SC-- except, the black guy who had it before me put a N/A bottom end in mine.

-Ghost
That does suck - take it you don't like him too much. I bought a car from a rich white guy who said he did stuff to my car to fix it and found that he paid for the cheapest parts avail. and they broke pretty soon after I got the car.

Stephen

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- I'm sure more to come... TOTALED

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post #18 of 27 (permalink) Old 10-28-2008, 06:23 PM
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Well, the car was at the end of its life, it had just shy of 200,000 miles when it died. But it is a mystery what the hell was put on that car, it was a mess when I bought it. When I bought it, the dashlights didn't work. After installing a set of fuses it was fixed-- until I started working on the stereo system and saw the nightmare that awaited me there.
And then there was the fun of trying to smog it

it was a 5-speed SC. Best car ever. RIP supercoupe

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post #19 of 27 (permalink) Old 11-02-2008, 08:00 AM
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Quote:
Originally Posted by David Neibert View Post
Used BHJ balancer with steel inner hub...is okay to reuse. OEM balancer with aluminum inner hub...not okay to reuse. The aluminum hub is the biggest problem with the stock balancer.

David
And... it's all fixed! Installed used '88 tbird 3.8 V6 OEM balancer with STEEL inner hub. (This only applies to 3.8 NA cars as it would seem NA=externally balanced, SC=fully internally balanced?)

Why ford switched from steel to aluminum at some point..... And ESPECIALLY on supercharged models with the additional pulley load as well ????? WTF!
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post #20 of 27 (permalink) Old 11-07-2008, 04:43 PM
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Good work!

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post #21 of 27 (permalink) Old 11-09-2008, 09:56 AM
 
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My crank was new reman from Atlanta Crankshaft, and is definitely a forged SC crank.

Mine snapped in the same spot after 10k miles.
I built the motor myself, about my 30+ full rebuild that I've done over my life so I have experience.

I found that three main things seem to cause this...
1- Using a crankshaft that has been turned more than .020 on the journals, especially the rods. They claim to be weakened to the point of failure, even with stock boost pressures.
2- The crankshaft has been machined but the radius is not cut correctly on the rod journals.
The radius for these cranks I'm told, requires special stones that unless you do Ford 3.8 cranks, the radius will be wrong, causing a binding effect. I'm not real sure about this but SCCOA has some more info on the topic.
3- Unknowingly using a cast crank from an NA motor. This can only be done by purposely regrinding the rear main to a different size than a standard crank. It was made different by Ford so they can't be mistakenly used in the SC block.

Forgot one big one, DETONATION... I did not have any issues with this, but it appears to be a real crank killer.

There are easy ways to test if you have a forged crank, but the easiest way is to tap with a hammer and see if it pings. If it does it's forged, if it thuds it's likely cast. Also the cast will be duller then a forged which is shinier from the maching done vs. the cast surfaces.

Be careful finding another crank.
As I found, they're not all as good as they appear, even the forged.

Last edited by Go_SC_Go; 11-09-2008 at 09:57 AM. Reason: added content
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post #22 of 27 (permalink) Old 11-08-2013, 08:01 AM
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alot of guys have tried swaping in a cast 4.2 truck crank as a stroker kit, some have more luck than others, thats the first thing id make sure of because if its a truck crank you will need most likly rods and pistons too. you cant just bolt a new crank in a its good to go.

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post #23 of 27 (permalink) Old 11-13-2013, 07:53 PM
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Hmmmm.....this post was from 2008.......

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post #24 of 27 (permalink) Old 11-13-2013, 09:38 PM
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Hmmmm.....this post was from 2008.......
LOL

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post #25 of 27 (permalink) Old 02-23-2014, 07:20 PM
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oh yea.....2008 im just trying to liven things up a bit here..... I don't see anything recent and I cant post new topics yet.

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post #26 of 27 (permalink) Old 02-24-2014, 09:35 AM
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FWIW, I've seen two snapped crankshafts in two vehicles I've owned in my time.

One in a 1986 Ford Thunderbird with a 302 and one in a 1969 Pontiac Grand Prix with a 400.

~Rick

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post #27 of 27 (permalink) Old 04-05-2014, 10:27 AM
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Is the balance issue the same on the 4.6L? I'm installing underdrive pulleys and wondering if I should have a new balancer on the way. Sorry if I'm lacking posting etiquette.
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