FYI FORD MustangSteve's Ford Mustang Forum / Crank Casualty

**Posted by rpm** 6/11/2018 9:24 PM

I used the MS trick with RTV to fix the oil leaking from the pan after I gave up on the $40 one piece gasket. However I still had an annoying leak from the rear seal area. I was fed up enough that I tackled the leak by trying the replace the rear seal while it's in the car method. Dropped the pan and rear main cap easily. Couldn't get the seal half in the block to budge.

Took a break and inspected the rear main bearing. Hmm, say some marks and flecks that looked suspicious. Emaied the pics to my brothers and nephew, who is a mechanical engineer and gear head in Austin (see, I have Texas roots). None of my brothers thought it warranted further thought. My ME nephew said he'd have an oil analysis done on it.

I ordered an oil test kit from Blackstone, and while I waited on it I thought I'd check the other main bearings. The #4 main looked fine, but when I removed #3 which controls the end play, OY!

That lower crank journal edge should not have an outer edge me thinks. So how does an iron crank wear more than the soft non ferrous bearing? I bolted up the mains and checked the end play, .045". It was .005" when built.

Internet search showed this is a common problem, especially with aftermarket cranks, due to thrust caused by insufficient clearance between the flex plate, converter and crank, or a bad converter. My brother in Fresno called his machinist who also drag races, who said in his experience it's always been the converter. I measured and had plenty of clearance between the crank, flexplate and converter, so I'm hoping it's the converter. I'm praying it's the converter.

So I drove the crank to Fresno today for them to repair it. I'll tear the motor down for a cleaning, buy some bearings, a converter and maybe some head studs. Who's converter would you guys recommend? Ya Ya, I know, put a 5 speed in it. This Mach 1 came from San Jose with an auto, and I want to keep it bone stock

**Posted by TKOPerformance** 6/12/2018 4:09 AM

That's a new one. I agree that I can't see how the crank wears more than the bearing. Are you sure this wasn't a machining problem with the crank?

**Posted by Bolted to Floor** 6/12/2018 7:21 AM

Bob, that’s puzzling.

What brand aftermarket crank do you have? Is it still a stock stroke?

I’m having trouble picturing how the converter can cause thrust issues. I presume this is on the back side of the bearing and the crank has been pushed forward. The flex plate bolts to the crank with no real way to move. On the last auto I installed, the converter was pushed back on the input shaft as far as it would go while out of the car. Once the slush box was bolted to the engine, the converter was pulled forward to bolt to the flex plate. What am I missing here?

**Posted by TKOPerformance** 6/12/2018 7:50 AM

Its not uncommon for a converter to cause thrust issues, because if the converter is in effect slightly too long it is jammed in there and applies force to the weakest link in the chain, which is the soft thrust bearing. BUT, why is the bearing okay and the crank undercut? That's what makes no sense.

**Posted by Bolted to Floor** 6/12/2018 7:55 AM

TKOPerformance wrote:
Its not uncommon for a converter to cause thrust issues, because if the converter is in effect slightly too long it is jammed in there and applies force to the weakest link in the chain, which is the soft thrust bearing. BUT, why is the bearing okay and the crank undercut? That's what makes no sense.

Thanks for the explanation.

This brought up another question for Bob, what brand bearings were installed?

**Posted by Bullet Bob** 6/12/2018 9:23 AM

rpm wrote:
This Mach 1 came from San Jose with an auto, and I want to keep it bone stock

Really? You mean with that "bone stock" 393 stroker? And the "Bone Stock" beautiful home-brew front suspension? And uh, that that "bone stock" roll cage? Okay, I get it, Bob. Bone stock like I did the Heap...it came with an auto-box also.

BB

**Posted by MS** 6/12/2018 9:54 AM

Looks like the counterweight on the crank was forced or dropped on the side of the bearing when installing it as evidenced by the two dented areas on the edge of the bearing. That probably cracked the bearing.
The rest could be due to the damaged bearing having less clearance, or your torque converter theory.

**Posted by Greg B** 6/12/2018 12:23 PM

Bolted to Floor wrote:
Bob, that’s puzzling.

What brand aftermarket crank do you have? Is it still a stock stroke?

I’m having trouble picturing how the converter can cause thrust issues. I presume this is on the back side of the bearing and the crank has been pushed forward. The flex plate bolts to the crank with no real way to move. On the last auto I installed, the converter was pushed back on the input shaft as far as it would go while out of the car. Once the slush box was bolted to the engine, the converter was pulled forward to bolt to the flex plate. What am I missing here?

Excessive hydraulic pressure in the transmission pushing the torque converter forward. Like a valve body restriction, trans brake. Assuming the torque converter was installed properly.

https://www.dragstuff.com/forum/viewtopic.php?t=4869

Last edited by Greg B (6/12/2018 12:33 PM)

**Posted by rpm** 6/12/2018 12:23 PM

TKO
Some internet searches say that these Red China cranks have poor machining on the sides of the crank journals which slings the oil out. Even if true, it wouldn't account for the thrust damage on mine.

Bolted
The crank is a Scat 393 stroker.
The flexplate, as its name implies, flexes. If the snout on the converter isn't machined deep enough for the recess in the crank end, it will bottom out and push the crank forward. If the converter balloons at rpm, it will also push the crank forward. I had no idea these were common problems till I had mine.

TKO
The bearing is not ok, it's just not as bad as the crank I agree that the crank wearing more than the bearing makes no sense.

Bolted
The bearings are Clevite 77 P

Bullet Bob
See? You are one smart cookie. No explanation needed.

MS
My brother and I assembled the motor short block, clearanced the block in a few spots where the rod caps interfered at the oil pump mount and cylinder skirts, fly cut the piston tops, and thoroughly cleaned the block and parts. Before final assembly I installed a new set of bearings. While the crank was R&I'd several times duriing the build, it was never dropped, or dropped onto the bearings. I just had my hands on the damaged bearing and there are no dents on it. Not sure what area of the bearing caught your attention, maybe the pic below is it. Sometimes pictures are deceiving. Even if the bearing was damaged, I can't see how that would cause the thrust force needed to cause the wear to the crank. An engine alone does not make thrust.

This piece of bearing was separating from the thrust side which I pulled away before taking the picture.

**Posted by rpm** 6/12/2018 1:01 PM

Thanks for the link Greg, good to know info. I've no idea what my pressure is currently, but I will check it. I had a trans guy friend rebuild it years ago. The converter was installed by my neighbor, a Ford mechanic of 40 years. I did hear and see it click into its final spot.

**Posted by TKOPerformance** 6/12/2018 1:38 PM

Yeah, I'm stumped on that one. How cast iron or steel wears more than babbit is beyond me. I'd expect at the very least to see nothing but copper on that side of the bearing.

**Posted by red351** 6/12/2018 2:41 PM

Just pulled a 302 apart where the thrust side on the crank and bearing looked the same as pictured. The radius cut on the crank was taking a good share of the thrust load. Metal fragment off the crank radius was most likely (my guess) what cuts into the cast iron.

**Posted by TKOPerformance** 6/12/2018 3:47 PM

Was any iron material embedded in the thrust bearing surface? I'm wondering if it's getting the particles embedded and then working on the crank like oil lubricated sandpaper. That would explain why the bearing isn't as damaged as the crank I suppose.

**Posted by rpm** 6/12/2018 4:54 PM

The bearing thrush edge that was damaged is pretty darn smooth. The pics make it look like there are voids and built up chunks on it. The dark burned area is also smooth. An edge of transfer metal can be felt with a fingernail. The outer radius edge has what also looks like transfer metal, like the one in the first and third pic. The slivers can be pulled off, and the surface below is smooth. The slivers have the same magnetic attraction as the bearings, and not the main caps. I'm betting on it being part of the .020" worn of the edge of the main and being redeposited. My main area of concern is the cause of this meltdown. But ya, I've learned that the crank damage is common. Should've asked about it when I was at the shop. I'll try to remember asking when I pick up the crank.

I know a little about stick, mig and tig welding, but nada about welding cranks. So I axed them about what brand of welder they use. They use a Gleason, made for crank welding. Never heard of them before. The crank grinder guy said flux with the consistency of sand is sprayed on the arc, instead of an inert gas or a flux coated rod. Using different flux will change the hardness of the weld material. Crazy.

EDIT: I couldn't see or feel any iron on the bearing.

Last edited by rpm (6/15/2018 3:51 PM)

**Posted by MachTJ** 6/12/2018 7:06 PM

Two questions. How was the main cap orientated on the block- where the bearing tangs on the same sides on all caps . Lastly was crank endplay checked before or after the harmonic dampner was installed, and is there any wear on the back side of the timing chain gear?

**Posted by MS** 6/12/2018 7:22 PM

These are the marks I saw. If you installed the crank yourself, that is not likely the issue. Hope your problem gets worked out. I have the Scat forged crank. Is yours the cast or forged one?

**Posted by rpm** 6/12/2018 7:34 PM

MachTJ wrote:
Two questions.

How was the main cap orientated on the block-

-Correctly With the arrows pointing forward.

where the bearing tangs on the same sides on all caps .

-Yes, however with that tang metal forced back to the crank, I don't think you'd be able to rotate the crank if you were able to torque down the caps.

Lastly was crank endplay checked before or after the harmonic dampner was installed, and is there any wear on the back side of the timing chain gear?

-Yes, it was. The endplay was checked both before and after I installed the dampner.

-No damage or contact marks on the front cover.

**Posted by TKOPerformance** 6/12/2018 7:34 PM

The type of welding to which you are referring is spray welding; the best method for repairing cast iron. Its kind of magic.

**Posted by 6sally6** 6/12/2018 8:26 PM

rpm wrote:
, I know, put a 5 speed in it. )

My thoughts zak-lee!! J/K
Just the leak was the only indication you had sump-thin wasn't right?!!
If so............that's scary!
6s6

**Posted by 6sally6** 6/12/2018 8:29 PM

Bullet Bob wrote:
rpm wrote:
This Mach 1 came from San Jose with an auto, and I want to keep it bone stock
Really? You mean with that "bone stock" 393 stroker? And the "Bone Stock" beautiful home-brew front suspension? And uh, that that "bone stock" roll cage? Okay, I get it, Bob. Bone stock like I did the Heap...it came with an auto-box also.

BB

......OUCH!!!!!
6s6

**Posted by 6sally6** 6/12/2018 8:47 PM

I've "seen" stuff get spray welded(years ago!) butt know nothing about how it happens. I think there may be a little"black magic" involved!
What's the plan?
Spray weld/repair the crank and re install?!
How's the quality/cost of a new stroker crank?!? (Like Eagle?)
You kinda know what you got now....with new crank that advantage is gone.
Was the converter a "trick" piece or FoMoCo?!
From what I've read/heard most everything is Chinese-made....even if it sez Made in US of A.! (made there...machined here?!)
Sounds like you have some purdy-smart folks(and friends) on your side....That's a huge +! Hang-in-ther and let us know what happens.
6sally6

**Posted by rpm** 6/12/2018 9:50 PM

6sally6 wrote:
rpm wrote:
, I know, put a 5 speed in it. )
My thoughts zak-lee!! J/K
Just the leak was the only indication you had sump-thin wasn't right?!!
If so............that's scary!
6s6

Uh... Ya...
Somebody was definitely looking out for me. It very well could've been ugly, and expensive.

**Posted by rpm** 6/12/2018 10:10 PM

6sally6 wrote:
I've "seen" stuff get spray welded(years ago!) butt know nothing about how it happens. I think there may be a little"black magic" involved!

Black magic indeed. When I hear about stuff like those crank welders, I wonder how they got thinking to that point. Who even would think of spraying granulated flux into an arc???

What's the plan? Spray weld/repair the crank and re install?!

Yes, Weld the damaged area, polish the journals, then check and if they're within spec, if not, take them to .010 under.

How's the quality/cost of a new stroker crank?!? (Like Eagle?)

At least twice as much as a repair. Quality, who knows.

You kinda know what you got now....with new crank that advantage is gone.

Ya, I'm confident the repairs will be fine. That is, up until I fire it up.

Was the converter a "trick" piece or FoMoCo?!

Ya trick. It was the trick stock one delivered by Henry.

From what I've read/heard most everything is Chinese-made....even if it sez Made in US of A.! (made there...machined here?!)

That's also what I've read.

Sounds like you have some purdy-smart folks(and friends) on your side....That's a huge +! Hang-in-ther and let us know what happens.

Well, they're smarter than me, so...
I'll probably only let you know if all goes well. If not, I've got a 460/C6 combo I need to do sumpin wit.

6sally6

**Posted by Bentworker** 6/12/2018 10:20 PM

It’s only money...and it’s not even mine!

Some bearings and a crankshaft and you will be better than new.

**Posted by rpm** 6/12/2018 10:38 PM

MS wrote:
These are the marks I saw. If you installed the crank yourself, that is not likely the issue. Hope your problem gets worked out. I have the Scat forged crank. Is yours the cast or forged one?

Well, now that you point those out, yes I do see your point of view.

My Scat crank is cast. Shallow pockets. When I was first looking into the Scat crank, 393 was it. One day I googled scat, HOLY CRAP! I must have led a sheltered life by what I found.