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1989 Ford F-250 HD 4WD 460 EFI w/ ZF5 Manual
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Discussion Starter · #1 ·
Hi 460 Community!

This is my first post! I have an 89 F250 w/ 460 EFI & ZF5 Speed Manual - I bought it a week ago; owner said it had not run in 3 years. He claimed the mechanic told him that the cylinders were losing compression.

I tested all Cylinders and I am getting 125 + or - 5 on each Cyl 1-8. So Compression is good, but there is a loud knocking noise that sounded like it was coming from Cyl 4.
I read as much as I could on this forum about determining what it could be and this led me to a final ignition test to find out what the knock is or was, it is coming from a very low position in the engine below the Crank.

Based on another thread on here; I pulled each spark plug wire from the distributor cap while running, one at a time and found that Cyl 3 when disconnected stopped the knocking and vibration. As soon as I plug it back in the knocking resumes. I just changed out my oil this morning because I thought the knock was my Flywheel only to find it was my Piston/Rod Bearing.

My question is:
  • How feasible is it to replace the rod bearing while the motor is in the truck?
  • How do I determine the thickness of bearing I would need if I did it? I have seen videos on people doing it and it looks simple, but my mind says high risk.
  • I would do a complete rebuild but I am a beginner with mechanics and I plan to sell the truck and buy a 74 Gran Torino next week and I have a buyer lined up.
  • What do you recommend - is it prudent to just swap one rod bearing if possible? or should I do all of them? If I did, would doing it without pulling and resurfacing the crank be a bad idea?
  • Could I recycle my new oil? I just dumped AMSOIL Signature in there, and I regret not checking my cylinder beforehand.
  • To my knowledge the engine is original and the oil I pulled out of there was black.

Any help would be appreciated.

- Exodus BKG
Pacific Northwest Member
89 Ford F-250 HD 4X4 460 EFI
 

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Premium Member
Joined
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9,423 Posts
Hi 460 Community!

This is my first post! I have an 89 F250 w/ 460 EFI & ZF5 Speed Manual - I bought it a week ago; owner said it had not run in 3 years. He claimed the mechanic told him that the cylinders were losing compression.

I tested all Cylinders and I am getting 125 + or - 5 on each Cyl 1-8. So Compression is good, but there is a loud knocking noise that sounded like it was coming from Cyl 4.
I read as much as I could on this forum about determining what it could be and this led me to a final ignition test to find out what the knock is or was, it is coming from a very low position in the engine below the Crank.

Based on another thread on here; I pulled each spark plug wire from the distributor cap while running, one at a time and found that Cyl 3 when disconnected stopped the knocking and vibration. As soon as I plug it back in the knocking resumes. I just changed out my oil this morning because I thought the knock was my Flywheel only to find it was my Piston/Rod Bearing.

My question is:
  • How feasible is it to replace the rod bearing while the motor is in the truck?
  • How do I determine the thickness of bearing I would need if I did it? I have seen videos on people doing it and it looks simple, but my mind says high risk.
  • I would do a complete rebuild but I am a beginner with mechanics and I plan to sell the truck and buy a 74 Gran Torino next week and I have a buyer lined up.
  • What do you recommend - is it prudent to just swap one rod bearing if possible? or should I do all of them? If I did, would doing it without pulling and resurfacing the crank be a bad idea?
  • Could I recycle my new oil? I just dumped AMSOIL Signature in there, and I regret not checking my cylinder beforehand.
  • To my knowledge the engine is original and the oil I pulled out of there was black.

Any help would be appreciated.

- Exodus BKG
Pacific Northwest Member
89 Ford F-250 HD 4X4 460 EFI

You will have to pull the pan and assess the bearing journal and the rod.
If the bearing has spun in the rod big end the engine will have to come out.

Given the intensity of the sound you describe I would have doubts about repairing / salvaging the engine while installed.






Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
 

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Registered
1989 Ford F-250 HD 4WD 460 EFI w/ ZF5 Manual
Joined
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23 Posts
Discussion Starter · #3 ·
You will have to pull the pan and assess the bearing journal and the rod.
If the bearing has spun in the rod big end the engine will have to come out.

Given the intensity of the sound you describe I would have doubts about repairing / salvaging the engine while installed.






Scotty J. "AKA" The "Mad Porter"
"EMC 2006" 3rd place finisher
Ported BBF iron head specialist & Aluminum heads from all sources.
Custom ground cams
See our products in the Vendor for sale section
Customized crate engines
ParklandAutoMachine.com
R-H-P.biz
"Parkland Performance Auto Machine" Formerly RHP
(253)-988-6648
Parkland Auto Machine
Thank you for the input, you are right down the street from me! Could we collaborate on some work? I'd like to see some of your product offerings.
 
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