Wrist Pin Failure - Why and Now What?
#2407209
11/22/17 03:08 AM
11/22/17 03:08 AM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
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Morrow, OH
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To try and make a long story short, at least 4 wrist pins and associated rod ends are galled (I only took one apart and the galling was severe in the rod end and the pin was also toast).
This is my old detuned race motor that was in my street/strip car. Has old Arias dome pistons that had the dome cut down - the pistons look fine. I had the motor rebuild (and detuned) and it does not have a lot of time on it since the rebuild. The motor has home ported 906 heads on it and 9:1 compression.
Took the motor apart because it had a very annoying noise in it that was driving me nuts and the converter went south so I decided to go back with the original 383.
Was getting ready to reassemble this motor (no plans for it other than a viable spare and was tripping over the parts) when I found the bad wrist pins.
The pins are floating. What would have caused it and now how do I fix it on the cheap?
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2407220
11/22/17 05:05 AM
11/22/17 05:05 AM
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Joined: Aug 2003
Posts: 43,163 Bend,OR USA
Cab_Burge
I Win
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I Win
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Bend,OR USA
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Two things can lead to galling, lack of oil and lack of adequate clearance for the oil to go into the pistons, wrist pin bores and rod pin bores Or maybe even bad oil I would see about honing the pistons, rod pin ends and polishing the pins to see if they are savable I hope so I like loose wrist pin to rod pin bushing clearances, .0010+ on .990 pins, more for bigger pins
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2407235
11/22/17 07:55 AM
11/22/17 07:55 AM
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Joined: Sep 2014
Posts: 4,457 Washington
madscientist
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I've seen pins that were bending gall like that.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
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Re: Wrist Pin Failure - Why and Now What?
[Re: B G Racing]
#2407342
11/22/17 01:25 PM
11/22/17 01:25 PM
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Joined: Nov 2003
Posts: 1,839 NW Indiana
fbs63
top fuel
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top fuel
Joined: Nov 2003
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NW Indiana
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Are they 1.094 or .990 od? Trend and others have oversized wrist pins available. IDK about 1.094 but I know they have them in .991 to .994. Also look and see if the pins have forced pin oilers. On a street car you need it for sure.
Last edited by fbs63; 11/22/17 01:27 PM.
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2407398
11/22/17 03:50 PM
11/22/17 03:50 PM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
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Thanks for all the replies. Since those are stock rods they owe me nothing and they have not had an easy life.
For $400 I will put in a set of Scat rods that are bushed. I wonder if some of the issue was the fact that the rod was not bushed.
Will suck it up and re-balance the assembly.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2407406
11/22/17 04:00 PM
11/22/17 04:00 PM
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Joined: Feb 2005
Posts: 20,174 PA.
pittsburghracer
"Little"John
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"Little"John
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Thanks for all the replies. Since those are stock rods they owe me nothing and they have not had an easy life.
For $400 I will put in a set of Scat rods that are bushed. I wonder if some of the issue was the fact that the rod was not bushed.
Will suck it up and re-balance the assembly. When we used to run our stock rods like that (unbushed) years ago we would drill a 1/8 hole in the top of the rod and champher it to give the pin some oil. it helped some but not totally.
1970 Duster Edelbrock headed 408 5.984@112.52 422 Indy headed small block 5.982@112.56 mph 9.42@138.27
Livin and lovin life one day at a time
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Re: Wrist Pin Failure - Why and Now What?
[Re: pittsburghracer]
#2407410
11/22/17 04:06 PM
11/22/17 04:06 PM
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Joined: Mar 2006
Posts: 2,675 Mt. Eden Ky.
Hemi Allstate
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Mt. Eden Ky.
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Thanks for all the replies. Since those are stock rods they owe me nothing and they have not had an easy life.
For $400 I will put in a set of Scat rods that are bushed. I wonder if some of the issue was the fact that the rod was not bushed.
Will suck it up and re-balance the assembly. When we used to run our stock rods like that (unbushed) years ago we would drill a 1/8 hole in the top of the rod and champher it to give the pin some oil. it helped some but not totally. I know that some SBC and BBC came from the factory with floating pins and without bushings. 69 302 for example. The drill the top and chamfer was a common mod for those too. Mark
1996 Ram 1500 Sport 1968 road runner 1952 Sears Allstate licensed, pump gas, Hemi 5.98 @ 115.73 1.33 60 ft. The best is yet to come. Painless Performance / Street RODDER magazine Top 100 for 2019
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2407463
11/22/17 05:30 PM
11/22/17 05:30 PM
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Joined: Aug 2003
Posts: 43,163 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,163
Bend,OR USA
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Thanks for all the replies. Since those are stock rods they owe me nothing and they have not had an easy life. You have learned a valuable life lesson from this ,huh Buynig or choosing cheap parts in a non stock Hi Po motor will buy you future problems, usually Good luck from now on
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: Wrist Pin Failure - Why and Now What?
[Re: pittsburghracer]
#2407469
11/22/17 05:40 PM
11/22/17 05:40 PM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
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Morrow, OH
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[
When we used to run our stock rods like that (unbushed) years ago we would drill a 1/8 hole in the top of the rod and champher it to give the pin some oil. it helped some but not totally. These rods do have that mod.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Wrist Pin Failure - Why and Now What?
[Re: Cab_Burge]
#2407474
11/22/17 05:47 PM
11/22/17 05:47 PM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
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Thanks for all the replies. Since those are stock rods they owe me nothing and they have not had an easy life. You have learned a valuable life lesson from this ,huh Buynig or choosing cheap parts in a non stock Hi Po motor will buy you future problems, usually Good luck from now on You need to understand that when this motor was originally put together cheap aftermarket rods and cranks did not exist. It was a great motor. When we detuned it the crank went THUD when put on the ground so it got replaced. Other than that was a great motor for a very long time. The replacement motor is a 2001 megablock with Eagle parts. The new build is a new "The Block" with all Molnar internals. This is just a low power spare motor now.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Wrist Pin Failure - Why and Now What?
[Re: DoubleD]
#2407916
11/23/17 04:31 PM
11/23/17 04:31 PM
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Joined: Jan 2004
Posts: 8,255 fredericksburg,va
cudaman1969
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Back in the 80's we all ran the stock rods, heavy TRW pistons and floated the rods the same way - steel on steel with the 1/8th inch oiling hole. just about every engine I ran like that eventually galled the pins at the rod - we just changed the pins honed the rod and kept going. Nothing wrong with that old set-up it just had its limitation back then. Maybe the clearance changed as the pin got hotter and made it gall?
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2408015
11/23/17 08:56 PM
11/23/17 08:56 PM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
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For some reason I don't remember the pins to be floating when the motor was originally built but I could be wrong on that. Perhaps they got converted at some point.
I do remember that very early on during a rebuild found several pins blued. The machine shop honed the pistons/rod (not sure which) replaced a couple pins and cleaned one or 2 up. Never had a repeat problem until now.
These rods have seen 6800 rpm far too often - it might be a good omen for them to fail like this just so that I replace them with a reasonable rod.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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Re: Wrist Pin Failure - Why and Now What?
[Re: markz528]
#2408049
11/23/17 10:48 PM
11/23/17 10:48 PM
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Joined: Mar 2006
Posts: 2,675 Mt. Eden Ky.
Hemi Allstate
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You said the torque converter went bad. How is your thrust bearing looking. I have seen the wrist pins blue when the converter shoves the crank forward and rear face of the thrust gets it too of course.
Mark
1996 Ram 1500 Sport 1968 road runner 1952 Sears Allstate licensed, pump gas, Hemi 5.98 @ 115.73 1.33 60 ft. The best is yet to come. Painless Performance / Street RODDER magazine Top 100 for 2019
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Re: Wrist Pin Failure - Why and Now What?
[Re: Hemi Allstate]
#2410441
11/29/17 12:20 AM
11/29/17 12:20 AM
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Joined: Jan 2003
Posts: 4,270 Morrow, OH
markz528
OP
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OP
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Morrow, OH
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You said the torque converter went bad. How is your thrust bearing looking. I have seen the wrist pins blue when the converter shoves the crank forward and rear face of the thrust gets it too of course.
Mark Thrust bearing is not great and needs replacing. Not total toast but not good.
67 Coronet 500 9.610 @ 139.20 mph 67 Coronet 500 (street car) 14.82 @ 94 mph 69 GTX (clone) - build in progress......
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