Author Topic: 427 failure analysis. I think I found the problem  (Read 3780 times)

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AlanCasida

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427 failure analysis. I think I found the problem
« on: September 07, 2019, 08:54:48 PM »
I got the motor out today and as I suspected the thrust bearing is bad. It has about .050" end play in the crank. It looked like the crank was pushed forward really hard as all the wear was on that side. It also wore a pretty good groove in the thrust surface of the crank, about .030", that I am not sure can be repaired or not. I did some measuring and found the convertor is about .100" closer to the front surface of the transmission than my spare stock c6/converter  shows. That leaves only about .010" clearance once it is all together.
 Looking closer at the converter I noticed marks in the paint on the engine side that match up perfectly with the flywheel bolts. I laid the flywheel on the converter with a flywheel bolt in it and measured the clearance and it had about .050" clearance which is almost exactly the same amount of end play I now have in the crank. So what I think happened is the converter ballooned on me, pushing the crank forward and the flywheel bolts were acting as a stop. I don't have much experience with this but will using the trans brake cause this?   
« Last Edit: September 08, 2019, 03:24:20 PM by AlanCasida »

338Raptor

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Re: 427 failure analysis.
« Reply #1 on: September 07, 2019, 11:04:42 PM »
It probably did balloon. But that wouldn’t remove thrust clearance unless it ballooned so much it pushed the converter stub into the transmission pump. You will see evidence of this in the trans pump gear. So you need to remove and disassemble the transmission pump to check. 
I see your converter doesn’t have an anti-ballooning plate. So I assume the converter is a budget part and your engine makes good power. It takes some decent power and a pretty weak converter to make it balloon.
ERA 427SC Cobra: Iron ‘67 482 SOHC, TKX 5 speed, TrueTrac 3.31 IRS, Magnesium Halibrands, Avon CR6ZZ tires. 

1969 Shelby GT350, 4 speed.

1967 Mustang Fastback: Close ratio T56 Magnum, Fab-9, Wilwood superlite brakes, Torque arm rear suspension, TCI-IFS with shock tower delete, (Coming soon, FE motor TBD)

1970 F250 4x4 Mud Truck, 557 BBF, as cast P51 heads, 900 hp @6700rpm, 801 tq, Q16, C6.

2012 Cobra Jet Mustang factory drag car, 5.4 liter 4.0 Whipple, 970 RWHP.

1964 Galaxie 500XL, 35 spline 3.70 Strange S-Trac, 6R80, (Coming soon: Pond Aluminum 525 SOHC, 800hp)

AlanCasida

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Re: 427 failure analysis.
« Reply #2 on: September 07, 2019, 11:11:41 PM »
It probably did balloon. But that wouldn’t remove thrust clearance unless it ballooned so much it pushed the converter stub into the transmission pump. You will see evidence of this in the trans pump gear. So you need to remove and disassemble the transmission pump to check. 
I see your converter doesn’t have an anti-ballooning plate. So I assume the converter is a budget part and your engine makes good power. It takes some decent power and a pretty weak converter to make it balloon.
Thanks for the reply. Actually my converter is a quality converter and is supposed to have the anti balloon plate built into it. Also I compared it with my c6 unit and the converter stub on it is about flush with the flexplate but on this one the stub sticks out about .070". I am going to get ahold of him next week and see if he can give me some insight into what might have happened.
 
« Last Edit: September 08, 2019, 03:55:22 PM by AlanCasida »

338Raptor

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Re: 427 failure analysis.
« Reply #3 on: September 07, 2019, 11:21:03 PM »
That picture shows it better.  It looks like it has a billet cover so ballooning sounds very highly unlikely.
ERA 427SC Cobra: Iron ‘67 482 SOHC, TKX 5 speed, TrueTrac 3.31 IRS, Magnesium Halibrands, Avon CR6ZZ tires. 

1969 Shelby GT350, 4 speed.

1967 Mustang Fastback: Close ratio T56 Magnum, Fab-9, Wilwood superlite brakes, Torque arm rear suspension, TCI-IFS with shock tower delete, (Coming soon, FE motor TBD)

1970 F250 4x4 Mud Truck, 557 BBF, as cast P51 heads, 900 hp @6700rpm, 801 tq, Q16, C6.

2012 Cobra Jet Mustang factory drag car, 5.4 liter 4.0 Whipple, 970 RWHP.

1964 Galaxie 500XL, 35 spline 3.70 Strange S-Trac, 6R80, (Coming soon: Pond Aluminum 525 SOHC, 800hp)

67428GT500

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Re: 427 failure analysis.
« Reply #4 on: September 08, 2019, 01:50:39 AM »
Alan, I truly feel for you.  I hope the answer is clear so you don't have to pull it again.

                                                                      -Keith

blykins

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Re: 427 failure analysis.
« Reply #5 on: September 08, 2019, 06:06:46 AM »
Generally, thrust bearing failures are due to driveline issues.  If there's significant clearance and careful assembly, the failure will come from the trans side. 

Torque converter issues will cause it.  Clutch issues will cause it as well.  On some of my pulling truck engines, I will add an extra oiling groove to the face of the thrust bearing so that it gets more oil because the clutch gets slipped considerably. 

I'm assuming you had clearance on both halves when you assembled (need to be checked individually), thrust bearing was set upon assembly, etc.  If you had one half dragging, then it could have failed which would have dumped material into the other half.  I have had situations where the block side half had plenty of clearance, but the cap side needed to be clearanced in order to have end-play.
Brent Lykins
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My427stang

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Re: 427 failure analysis.
« Reply #6 on: September 08, 2019, 07:26:27 AM »
My response is sort of all over the map here, maybe the converter ballooned, maybe it didn't have enough space to begin with, but I would likely be asking about pressures, stall speed options, and limiting feed to the converter too if they think its appropriate, lots of tricks guys do to make them live and be consistent

Before that I would look very close at pilot hole alignment, it seemed to take a beating too, to include size of the hole, flywheel and converter "marriage", but I do think something is certainly there

Option 1 - The flexplate/balloon plate/bolt head/relationship was bad and you tightened the converter against the crank bolts and pilot hole.  This would cause the marks, but only cause thrust bearing failure if there wasn't enough room on the backside of the converter, jamming the crank forward.   I'd ask what you see on the pump side of the converter, maybe there are some tracks

Option 2 - It all fit great and the converter grew. Possible, and happens, but IMHO you likely aren't making the power for that unless you have a tranny problem or the wrong converter, because it is an antiballoon converter.  Diameter matters, and maybe with the transbrake, the converter just doesn't have the capacity for the launch RPM and you were driving it to the limit for that size converter and it grew.  It also could be that you weren't binding, but didn't have enough room for it as it was at pressure.  There is movement there. 

The hard part is, regardless of the scenario above, indications will be the same, converter pushes on front pump and crank, thrust goes out, so you may not find THE answer, but you may find where your setup was marginal and give it wiggle room

I am not an AT guy, but I understand that dump valves and limiting converter feed is common, I also think that if you are at the limit of the converter, adding a couple hundred RPM or more of stall might help make things live longer.

Keep in mind, getting all the way to true stall speed (and the internal pressures associated with that) with a transbrake will be higher and greater than footbraking, so if the converter wasn't designed for that, it could be working pretty hard driving option 2 above

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Ross
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CaptCobrajet

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Re: 427 failure analysis.
« Reply #7 on: September 08, 2019, 08:26:18 AM »
Definitely take just the converter only and see if the pilot slides easily, all the way in the back of the crank.  If not, get clearance so it will.  When you put it all together, and the bolts(or studs) are all in place but not tight, and with the bell housing bolts tight,  you should be able to slide the converter all the way back towards the pump and get .120 between the flexplate and converter.   If more than .120, shim it.  If less than .120, this could be your issue.  If too tight, you may have to have Broader adjust the pilot length on the converter.  If you shim it, measure your shims carefully and get them all the same thickness within .001 of each other.  Wobble on a big circle like that can take out the pump bushing.
Blair Patrick

AlanCasida

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Re: 427 failure analysis.
« Reply #8 on: September 08, 2019, 12:02:44 PM »
I looked at it some more this morning and even with the input shaft removed the mounting flange on the torque converter is still about .080" closer to the mounting surface of the C6 than a stock converter. I also tried a B&M converter I had and it was the same dimension as the stock converter. I also noticed on the rear of the input shaft there are what looks like rub marks like it was bottomed out. When I pulled the motor I was able to pull it straight forward away from the trans and when I checked the converter it was pushed completely back. Also I think those bolt marks on the converter might be a little misleading. I briefly had my 428CJ motor in it and it had that reinforcement washer on the flywheels bolts and it is .120" thick so that might be where that came from. I just hope I didn't screw it up too. I just looks like the converter I am using is too thick dimensionally although I haven't found where yet.
 I guess the other question is, is my 428 crank salvageable and at what cost? Can the thrust area be welded up and remachined?
« Last Edit: September 08, 2019, 03:56:24 PM by AlanCasida »

AlanCasida

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Re: 427 failure analysis. I think I found the problem
« Reply #9 on: September 08, 2019, 03:29:06 PM »
I was looking at the converters I had real close to see where I was losing the distance and I noticed the stock and B&M converters had a chamfer on the part of the snout that engages the pump where the converter I am using did not. So I sanded/filed chamfers into the snout on it and lo and behold it now reads the same depth as the others.  Needless to say I am not real happy right now. Grrrrrrrr.
Thanks, everyone for your input. As always, it is greatly appreciated.
Here are a few pics.
Pic #1 is of the B&M converter
Pic#2 is of the converter I am using
Pic #3 is of the converter I am using after I sanded a chamfer into it.
 
« Last Edit: September 08, 2019, 03:54:38 PM by AlanCasida »

338Raptor

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Re: 427 failure analysis. I think I found the problem
« Reply #10 on: September 08, 2019, 04:59:31 PM »
You still need to pull the trans pump and inspect the pump housing/gear surface.  If it applied enough pressure to wipe out your crank, it definitely damaged the trans pump gear.
ERA 427SC Cobra: Iron ‘67 482 SOHC, TKX 5 speed, TrueTrac 3.31 IRS, Magnesium Halibrands, Avon CR6ZZ tires. 

1969 Shelby GT350, 4 speed.

1967 Mustang Fastback: Close ratio T56 Magnum, Fab-9, Wilwood superlite brakes, Torque arm rear suspension, TCI-IFS with shock tower delete, (Coming soon, FE motor TBD)

1970 F250 4x4 Mud Truck, 557 BBF, as cast P51 heads, 900 hp @6700rpm, 801 tq, Q16, C6.

2012 Cobra Jet Mustang factory drag car, 5.4 liter 4.0 Whipple, 970 RWHP.

1964 Galaxie 500XL, 35 spline 3.70 Strange S-Trac, 6R80, (Coming soon: Pond Aluminum 525 SOHC, 800hp)

winr1

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Re: 427 failure analysis. I think I found the problem
« Reply #11 on: September 08, 2019, 11:33:40 PM »
An oversized thrust can be had

How many thousands do you reckon the crank thrust would need to clean up ??

You could make a shim as well



Ricky.

AlanCasida

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Re: 427 failure analysis. I think I found the problem
« Reply #12 on: September 08, 2019, 11:45:36 PM »
An oversized thrust can be had

How many thousands do you reckon the crank thrust would need to clean up ??

You could make a shim as well



Ricky.

I think the groove in the thrust is around .030 deep. I haven't taken it out of the block yet. I am hoping it can be welded up and remachined. My machine shop does that on certain cranks but I am not sure if they can do it on this one.

manofmerc

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Re: 427 failure analysis. I think I found the problem
« Reply #13 on: September 09, 2019, 04:13:24 AM »
Sadly I have experienced something similar.On my 427 comet my flexplate was busted making a terrible noise .I pulled the engine and my crankshaft thrust was wiped out .I began to inspect the torque convertor (TCI) I could see where the input shaft was making contact inside the convertor .There was my smoking gun .Basically tci didn't make my convertor correctly it was to short .It wasn't an inexpensive convertor either .Well another crankshaft (428) bearings oil gaskets a bulletproof ATI flexplate and 10" ATI convertor .I was back in business .I come to find tci used a Chrysler convertor because it was furnace brazed and made it fit a c-6 .They just missed the mark by a few thousands .And then there was another tci convertor of mine that wiped out the crank in my 460 comet dragcar because it ballooned .After those issues with tci I went with ati no issues so far .So sorry for you Allan you will get it fixed .You really have to be aware of all dimensions with aftermarket convertors.Some how I think those flexplates bolts were rubbing from the beginning .A fellow racer has had the same issue with his c-4s and he lost a couple of cranks as well.Aftermarket parts are really let the buyer beware !Doug

gt350hr

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Re: 427 failure analysis. I think I found the problem
« Reply #14 on: September 09, 2019, 11:08:12 AM »
     Torque converter modifications can cause "forward pressure" when the fin angles are altered. That is a common way to gain stall ( obviously) along with stator alterations and clearances. This can happen in high stall and also low stall ( towing) converters. The "pump" ( back half fins welded to back cover) and turbine ( loose that are splined to the input shaft.) "should'' cancel out any forward thrust but this isn't always the case. Trans brakes also cause thrust bearing wear much like a super heavy clutch. Lack of end play is a very bad condition that certainly added to this failure. Both conditions can be fixed since obviously every racing converter doesn't cause this. Just my two cents of personal experience.
   Randy