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Old 11-22-2020, 07:41 AM   #1
rally 1
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Default Engine knock

Working with a new A owner on a car that has been stored for 30+ years.
Engine was rebuilt 30 years ago, sleeved to std. bore, one piece guides, adjustable lifters, new babbitt, pistons, etc.
Doesn’t appear to have more than a couple of hours run time.
Pronounced knock when running, increases with RPM.
Isolating knock to bottom end, we removed pan.
What was found, side clearance on rods was .020” +.
Further inspection found bearing clearance to be spot on at .0015”, however, the rod journal width measure 1.632” (1.620” spec) wide.
Crank thrust measures .004”

So, the question, can rod babbitt be pored and machined +.010 wider than stock, any shop suggestions?
Or do I need to just replace the crankshaft?
New owner has budget concerns, so thoughts on best avenue to solve this issue.
Thanks
ken
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Old 11-22-2020, 08:15 AM   #2
nkaminar
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Default Re: Engine knock

A rod knock with side clearance would indicate a bent rod. As the piston goes up and down it forces the rod back and forth on the journal. Take the rod to a good machine shop and have them check for a bent rod. Bring the piston pin too as they will need that to check the rod. If you want you can just leave the piston on as they can remove it. The rod can be bent to straighten it out. Otherwise, the 0.020 side clearance should not cause any issues.
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Old 11-22-2020, 08:37 AM   #3
rally 1
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Default Re: Engine knock

Thanks,
Will definitely check rod alignment. We just pulled all the piston/rod assemblies but havent disassembled.
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Old 11-22-2020, 11:56 AM   #4
Jack Shaft
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Default Re: Engine knock

excessive rod endplay a cheap fix is to dabble some solder on the rod thrust faces and fit them...
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Old 11-22-2020, 06:55 PM   #5
Jim Brierley
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Default Re: Engine knock

I agree with Nakimar. Check the alignment, don't worry about the side clearance. While you have it apart, insure that all parts are in the that are supposed to be there. I've seen more than one engine with missing parts, front crank slinger, hold-down spring for the dist. drive gear as an example.
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Old 11-22-2020, 09:16 PM   #6
Jack Shaft
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If the rod was bent the side clearance measurement wouldn't be true
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Old 11-22-2020, 11:36 PM   #7
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Default Re: Engine knock

I would think if the tolerances were that close, you wouldn't have a noticeable bearing knock. If engine was sleeved, it was also decked. I would also look carefully for any indication of piston interference with the head
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Old 11-23-2020, 06:28 AM   #8
rally 1
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Default Re: Engine knock

No indication of pistons hitting cylinder head.
Front oil slinger was missing, cam gear had a big gouge in it where the timing dimple was, we replaced both prior to starting the engine.
Internally the engine has new pistons/rings, camshaft and adjustable lifters, stainless valves with one piece guides.
As stated, the rod pin measures 1.632” on all four.
While watching rods/crank while turning engine over with pan off, all four rods move back and forth on the journal.
At this time, we’ve decided to pull the engine and inspect everything.
Better safe than sorry.
Thanks for the responses.

Ken
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Old 11-23-2020, 11:22 AM   #9
rally 1
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Default Re: Engine knock

Update:
All four connecting rods are twisted .003-.0045, pin not parallel to crank. When these rods were removed from the engine, excessive torque was required to loosen. Had to use a two foot breaker. OEM style nuts with cotter keys were installed.
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