anyone else ever have have an issue with an SC crank breaking?

[Drozz30]

A few weeks ago i was on my way home from work when my car made a loud noise and died. When i started checking things out i noticed it turned over very easily. Come to find out the remanufactured crank i just put in last sumer snapped off between the first two rods. Damn thing only had around 15000 miles on it. Is this a common thing to happen with remanufactured crank shafts?

[getblown]

Yeah, just recently (month ago) with a REMAN FROM JASPER!

Before the 5spd swap, I backed out of the driveway, stomped on it and spun, so I let off and got back into it and I guess getting back into it broke it into 2 pieces. Its an odd feeling when your cranking, but your belts arent moving.

Right between the 1-2 journals, fortunatly for me (again) jaspers broken motor is under warrenty.

http://i18.photobucket.com/albums/b140/getblown/DSCF2045.jpg

http://i18.photobucket.com/albums/b140/getblown/DSCF2042.jpg

jOe

[Hock]

I have issues with Reman'd cranks for our cars. Most I'm sure are welded which really does nothing for the strength. We should try to find a company that will make them new for us and anybody else with a 3.8/4.2 based engine.

[the-big-e]

You can get replacements from someone here on the boards...

I have three or four of them (SC engines) out on the floor with at least three more still in my parts cars.....

I do have one crank that is not within specs and it serves as a door stop right now.....

[Jim Demmitt Jr]

Stock 90 SC Crank

I never broke a crankshaft I had mine re-chromed and radious ground it stood up to 7000rpm's running 11.90's and 10.60's 5 years of hard running

[Hock]

Stock 90 SC Crank

I never broke a crankshaft I had mine re-chromed and radious ground it stood up to 7000rpm's running 11.90's and 10.60's 5 years of hard running

Jim, their talkin about those reman jobs.

There really shouldn't be much of a problem with a stock crank unless its stressed from over use and to much power. At least thats my opinion, I could be wrong.

[Mike8675309]

My guess is that nearly every block that shows up at a generic rebuilder has had the crank stressed. if they grind them and put oversize bearings in them, they could easily get through the nitride hardening which will make it much more fragile. If they don't redo the fillets when the grind the crank, and do them properly, they'll also add a new point for stress to focus.

My crank came out of the 93 with over 150k miles still in great shape. I actually had them try to polish it a little to loosen up stock bearing clearances which mic'ed out a bit tight.

[Drozz30]

Yeah, just recently (month ago) with a REMAN FROM JASPER!

Before the 5spd swap, I backed out of the driveway, stomped on it and spun, so I let off and got back into it and I guess getting back into it broke it into 2 pieces. Its an odd feeling when your cranking, but your belts arent moving.

Right between the 1-2 journals, fortunatly for me (again) jaspers broken motor is under warrenty.

jOe

Yeah thats pretty much the same way mine went. got into it a bit then let off and when i started to step on it again it shut right down.

[getblown]

Yeah thats pretty much the same way mine went. got into it a bit then let off and when i started to step on it again it shut right down.

Yeah, i figured it was just the loading and unloading that did it, glad I'm not the only one.

jOe

[Tim Groth]

I'd say mine might be added to the list once I get to tear into it...its FUBAR'd and threw a rod or two out of the pan...been to sick to even start tearing it apart to be honest.

-Tim

[pro street rich]

Both broke between the first and fourth rod area. One broke clean thru, the other broke so that it all still turned, but it moved forward and the crank pickup was then out of range. Both of these engines were never apart before they broke. Also for what it is worth. both engines were not running stock blowers or other bolt on's........Rich

[dwayne]

no i never broke a crank.

[al35thsc]

In the same boat as Rich. Broke 2 in the 35th within a year of each other :D I figure they didn't redo the fillets.

[XR7 Dave]

In the same boat as Rich. Broke 2 in the 35th within a year of each other :D I figure they didn't redo the fillets.

This is a very good point. As you can see the above crank broke right on the fillet. I've seen some pisspoor crank grinding jobs from some supposedly very reputable shops (not from any SC specialists mind you). Just another one of those "not familiar with the V6" things that we run into all the time. There are some very high HP motors out there running just fine on .010" under cranks but I think that the grinding process may be key here.

Another tidbit that may or may not apply is that the bearing companies only offer up to .020" under main bearings but they offer up to .040" under rod bearings. I only use a max of .010" for either for the engines I build. Ford recommends not cutting the rear main at all because of it being already cut .010" from the factory but I have never heard of any rear main failures.

[quick35th]

Both broke between the first and fourth rod area. ........Rich

My old 35th that Sean now owns snapped its crank in the same place.

Shane
Glynn Motorsports

[BlackbirdSC]

If reground properly, a .040" under rod would be stronger than std. If the extra space was used to make the fillet larger, it would be stronger. The diameter has nearly nothing to do with it. Even .040" is a fraction of a fraction of a % of material being taken away.

There's a reason race cranks run .125" fillet radi. And how SB Chevy's can make 800-1000 HP on 1.8-1.88" rod journals.

And alot of shops don't pay attention to fillet's. They make the grinding wheels nice and sharp on the sides which cuts away the fillet and weakens the cranks. Some crank grinders have wheels that are 4' or more in diameter and shops don't like refacing them to grind 1 or 2 performance cranks. So you almost have to know someone to get it done 'right'.

Ford made a rolled fillet on the 4.6 cranks that's recessed below the journal surface. That's how a stock cast 4.6 crank can withstand 100s of HP over stock.

P.S. GM 4.3 V6s have problems with cast cranks breaking in the same 1-2 rod journal area. The tech bulletins claim the belt tensioners are too strong and years of pulling the crank snout to the side make them break. So it's just a even fire V6 thing.

[19TbirdSC91]

Yep, just put a new motor in that 35th cuz it broke in that same spot at just over 1000 rpm... i'll post a pic of the broken piece later.

Sean

[dirtybird91]

I swear I just came from Ikey Maynard's house today (can't remember his user-name) and he showed me how his crank was snapped. Weird
I have an old shortblock stored away at my freind's barn. I will be gathering that for him so that he will have a good stock crank now that I don't own an SC.
:o
Frank