This is a pic from my girdled stroked 109 block, notice the discoloration on #1 journal? I believe this is a cat forged crank, I did drive the car about 4 miles after it broke. I didn't know at the time that I had broken the crank, can that be the reason for discoloration ?
Broken crank
- Thread starter seeya v6
- Start date
- Joined
- May 26, 2001
For the crank to be discolored, it must have been really hot, and there was not sufficient oil flow to keep it cool?
There are various other possibilities such as the main line bore being off, or a cap, or the girdle putting the crank in a bind?
Check closely on every step of the tear-down and inspect each part. It will require a bore gauge to check the main line though.
It would be nice to know how many miles, and how the car was used since the build was completed?
There are various other possibilities such as the main line bore being off, or a cap, or the girdle putting the crank in a bind?
Check closely on every step of the tear-down and inspect each part. It will require a bore gauge to check the main line though.
It would be nice to know how many miles, and how the car was used since the build was completed?
3.8L V-8 eater
Well-Known Member
- Joined
- Jul 22, 2006
I feel for ya man!!! The time and money it takes to build a stroker motor is no joke!! Good luck going forward!!
Thanks for input Nick......Second time this motor was built..first time I broke a piston and wasted #1 rod had crank fixed,Roughly 8,000 street miles on current build. Mostly roll racing on street, motor is being sent to machine shop for tare down for accurate diagnosis of death! I will post more pics as I receive them. It broke on a lite boost acceleration to check tranny down shift..then the car had a distinct vibration like the u joint was bad.
I had a crank break in the exact same location #1 and the exact same way. It ran, just like yours and only made a slight knocking sound I heard one day in a parking garage. It was on my wife's escort though, not a GN.
I think that that portion of the crank gets loaded some from the accessories on the front of the car, the front main bearing reacts the up and down load, but there is some bending that reaches that portion of the crank. That's why at the crack, you can see in the picture what looks like a 1/8" gap there. I bet, like mine the #1 bearing is torn up really well now and probably now if you remove all accessories you can move the broken snout of the crank up and down pretty well. Once cracked as that crank rotates, those surfaces rub relative to each other just like you see when you pull up and down on the detached end. I'm guessing that maybe the heat from the friction of these surface rubbing together has caused the discolorization you see. The portion towards the rod has much less material and would probably get a bit hotter. It's tough to see but I think there is a litte discolored area on the other beefie side as well. Just a guess.
In my case, I never found what was wrong for sure. I just put another crank and bearings in it, cleaned everything, put it together and drove it for a few years and maybe another 30k miles or so. The motor always ran like new after that. I never did allign hone the block, and the new crank rotated as it should, and all clearances checked OK ( for an escort of course). I have a feeling if there is excessive clearance in the #1 bearing it will load up that area of the crank and that extra clearance will contribute to cracks in that area. The problem is you can't really check it very well because that journal and bearing is destroyed when the crank snaps.
I think that that portion of the crank gets loaded some from the accessories on the front of the car, the front main bearing reacts the up and down load, but there is some bending that reaches that portion of the crank. That's why at the crack, you can see in the picture what looks like a 1/8" gap there. I bet, like mine the #1 bearing is torn up really well now and probably now if you remove all accessories you can move the broken snout of the crank up and down pretty well. Once cracked as that crank rotates, those surfaces rub relative to each other just like you see when you pull up and down on the detached end. I'm guessing that maybe the heat from the friction of these surface rubbing together has caused the discolorization you see. The portion towards the rod has much less material and would probably get a bit hotter. It's tough to see but I think there is a litte discolored area on the other beefie side as well. Just a guess.
In my case, I never found what was wrong for sure. I just put another crank and bearings in it, cleaned everything, put it together and drove it for a few years and maybe another 30k miles or so. The motor always ran like new after that. I never did allign hone the block, and the new crank rotated as it should, and all clearances checked OK ( for an escort of course). I have a feeling if there is excessive clearance in the #1 bearing it will load up that area of the crank and that extra clearance will contribute to cracks in that area. The problem is you can't really check it very well because that journal and bearing is destroyed when the crank snaps.
- Joined
- May 28, 2001
What balancer is on that crank? Loose?
Check the fillets on the other mains and rod throws.
Was that crank damaged at the same throw as we're seeing now?
Check the fillets on the other mains and rod throws.
Was that crank damaged at the same throw as we're seeing now?
I can see the black line in the picture that appears to separate the area that has been affected by the heat and not. However, it's not clear to me now which side of the black line has been affected by higher temperatures. When I first looked at it, it looked like the volume towards the crack had been at higher temps, but on second look, it seems that maybe the affected area is the other side of the black line. If this is the case then the "surface rubbing" theory is wrong as far as heating up the crank. If the area around the #1 rod bearing is where the discoloration is, as it appears to me now, then it seems consistent with heating up from a spun bearing.
- Joined
- May 28, 2001
Stock balancer?? IMO, a stock balancer has no place on an engine that's beat on as are most TR's.[Double/triple the designed HP/TQ] .Being a v6 doesn't help. V8's are bad enuf.
First failure could well have had affected the heat treat/integrity of the throw/main area.
750H.P.V6
Brutal 6 Racing
- Joined
- Sep 4, 2001
X 2 on this. What did they do to "fix" the crank the first time it was damaged? If the fix involved weld repairing the rod journal I'd suspect it played into the 2nd failure for the reason Chuck stated.
Neal
Last edited:
- Joined
- Feb 18, 2006
Something fishy going on.....
Flyin Brian
Member
- Joined
- Jun 18, 2011
I am leaning towards spun #1 rod bearing caused heat and then breakage.
- Joined
- Feb 18, 2006
The discoloration is a result of the crack IMO or the rod would be blue as well.
Honestly I would say there was some problem with that crank before it ever went into the motor. It took a hard hit somewhere....
Rick
Honestly I would say there was some problem with that crank before it ever went into the motor. It took a hard hit somewhere....
Rick
750H.P.V6
Brutal 6 Racing
- Joined
- Sep 4, 2001
The discoloration is more than likely from when the rod bearing spun last time since the crank was ground not weld repaired. If the discoloration was from something going wrong with the current engine build the big end of the rod would be blue also.
If I'm right, the fact that the crank got hot enough to discolor when the rod bearing spun originally changed the heat treatment and made it brittle leading to the subsequent failure on the 2nd engine build.
Neal
If I'm right, the fact that the crank got hot enough to discolor when the rod bearing spun originally changed the heat treatment and made it brittle leading to the subsequent failure on the 2nd engine build.
Neal
- Joined
- Feb 18, 2006
I don't know any builder that would reuse a crank that was blued like that without making it known upfront what the deal was.
Rick
Rick
With the cost of 4340 forged cranks now being very reasonable and the availability of stock vs stroker, I don't think that there will be any more crank repairs going on, other than minor cleanups, not journal /fillet repairs. I received a BMS crank back from Crankshaft Specialties in Memphis and it was returned in horrible condition on a journal repair. It is actually worse now than it was.The price to get it re-repaired is within a $150 bucks of a new crank. I don't think that crank will ever see oil again. I have never seen a crank break there before.
750H.P.V6
Brutal 6 Racing
- Joined
- Sep 4, 2001
I agree with you but I've always been amazed at what some people try to "save" over the years. Without knowing the condition of the crankshaft after it was originally damaged and what it looked like prior to installation it's anyones guess. It does seem coincidental that it was damaged on the #1 rod journal and then broke in the same area.
Neal
