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Old 07-17-2015, 08:45 AM   #1
oldwoodsman
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Question engine knock question

Just curious, at what clearances do rod and main bearings start to knock?
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Old 07-17-2015, 11:16 AM   #2
Patrick L.
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Default Re: engine knock question

I've seen [heard] them knock at .003" on other engines. These model A engines seem to be able to handle a little more before they get noisy.
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Old 07-17-2015, 05:03 PM   #3
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Default Re: engine knock question

Depends on oil viscosity, too. And oil temperature.
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Old 07-17-2015, 05:11 PM   #4
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Default Re: engine knock question

They put up a pretty good knock when the Babbitt in a rod decides to fall to the bottom of the pan in little bitty pieces.
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Old 07-17-2015, 05:28 PM   #5
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Default Re: engine knock question

RE; 29 Business Coupe -my engine was rebuilt before I bought the project , when I finally got it together and running it had a knock, determined it sounded like it was # 2 cylinder. I pulled the pan rolled the engine over and was able to see the rod was tight against the piston Boss , just had to pull that piston and had the boss machined for clearance , good as new now. might not be your problem , just sharing my results
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Old 07-17-2015, 08:36 PM   #6
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Default Re: engine knock question

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Quote:
Originally Posted by Dave Mc View Post
RE; 29 Business Coupe -my engine was rebuilt before I bought the project , when I finally got it together and running it had a knock, determined it sounded like it was # 2 cylinder. I pulled the pan rolled the engine over and was able to see the rod was tight against the piston Boss , just had to pull that piston and had the boss machined for clearance , good as new now. might not be your problem , just sharing my results

most likely this means the rod is bent, and that the piston is cocked in the cylinder
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Old 07-17-2015, 08:42 PM   #7
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Default Re: engine knock question

Hi Kurt,
What would cause tods to bend?
Regards
Chris
Cape Town
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Old 07-17-2015, 09:43 PM   #8
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Default Re: engine knock question

Quote:
Originally Posted by Dave Mc View Post
RE; 29 Business Coupe -my engine was rebuilt before I bought the project , when I finally got it together and running it had a knock, determined it sounded like it was # 2 cylinder. I pulled the pan rolled the engine over and was able to see the rod was tight against the piston Boss , just had to pull that piston and had the boss machined for clearance , good as new now. might not be your problem , just sharing my results
Dave I don't have a problem with my engine, just curious for future reference.
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Old 07-17-2015, 09:43 PM   #9
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Default Re: engine knock question

I've heard tell uf a "ROD BENDIN' GREMLIN"!--Sum times, he fills one cylinder clean full uf WATER & WHAMO!
Bill W.
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Old 07-18-2015, 08:48 AM   #10
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Quote:
Originally Posted by BILL WILLIAMSON View Post
I've heard tell uf a "ROD BENDIN' GREMLIN"!--Sum times, he fills one cylinder clean full uf WATER & WHAMO!
Bill W.
Probably dog Pee
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Old 07-18-2015, 10:28 AM   #11
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Default Re: engine knock question

Rod NOT Bent , machinist inspected , aftermarket piston problem
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