The Ford Barn

jhowes · 04-03-2018, 08:33 AM

I am wondering how the shade tree mechanic tests the wrist pins ( piston pins) If the engine is still in the car and the pan is removed

WRIST PINS OR PISTON PINS ARE SUPPOSED TO HAVE A VERY CLOSE TOLERANCE, SO HOW DOES THE SHADE TREE MECHANIC TEST THAT TOLERANCE??? THE PAN IS OFF THE ENGINE AND THE ENGINE IS STILL IN THE CAR?? I HAD A MACHINE SHOP DO MY PINS ON ANOTHER ENGINE AND THEY SEEMED TO BE VERY TIGHT BUT HOW TO CHECK THIS ON MY OWN IS THE PROBLEM. JACK

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100IH · 04-03-2018, 08:52 AM

First there 2 fits to look at, The fit of the pin in the piston and the fit of the pin in the rod bushing. For my money, the rod caps should be removed and the piston assy. needs to come out. At that point it's a feel thing. What does .0006 - .001 feel like. These are general ballpark numbers but are so slight that measuring ID & OD won't be practical unless you have your Sunnen pin fitting hone with the gauges in the garage.

jhowes · 04-03-2018, 09:32 AM

100IH, What does .0006-.001 feel like? I suspect "feels like no movement at all". So there is no way for the shade-tree mechanic to do this. Jack

jhowes · 04-03-2018, 09:35 AM

Sorry about the double post. Jack

100IH · 04-03-2018, 09:58 AM

No sense of wobble. sideways movement. pin to rod and pin to piston. A fair amount of drag when sliding in or out with light oil. A written description not as good as feeling the real thing and not as good as using the tools that are on the hone.

40 Deluxe · 04-03-2018, 10:51 AM

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The 'feel' of the fit varies with the individual. There is a "palm fit" and a "thumb fit", for example. Next, what is the temperature of the piston when you're checking it? Are you reaming or honing the pin bushings? Lots of variables! As 100IH says, best to let a machine shop measure if you have the slightest doubt.

George Miller · 04-03-2018, 11:13 AM

You would have to take them out. The best way is lessen to your engine before you tear it apart. If it has noise find out which cylinder. Then by sound at different rpms you can tell what it is. I never tear a engine apart with wrong noise going on tell I know what it is.

Kurt in NJ · 04-03-2018, 01:08 PM

By rocking the crankshaft and looking for movement, also a finger spanning both surfaces can feel slight movement--- sometimes even watching the oil squish out-- if it squirts out the side it's most likely too loose

Kahuna · 04-03-2018, 01:30 PM

With piston & rod removed, when piston is held horizontal, rod should drop slowly.

04-03-2018, 08:33 AM	#1
jhowes Senior Member Join Date: Jul 2010 Location: upstate NY near Mass border Posts: 789	Wrist pins I am wondering how the shade tree mechanic tests the wrist pins ( piston pins) If the engine is still in the car and the pan is removed WRIST PINS OR PISTON PINS ARE SUPPOSED TO HAVE A VERY CLOSE TOLERANCE, SO HOW DOES THE SHADE TREE MECHANIC TEST THAT TOLERANCE??? THE PAN IS OFF THE ENGINE AND THE ENGINE IS STILL IN THE CAR?? I HAD A MACHINE SHOP DO MY PINS ON ANOTHER ENGINE AND THEY SEEMED TO BE VERY TIGHT BUT HOW TO CHECK THIS ON MY OWN IS THE PROBLEM. JACK ///

04-03-2018, 08:52 AM	#2
100IH Senior Member Join Date: Dec 2011 Location: SW Idaho Posts: 970	Re: Wrist pins First there 2 fits to look at, The fit of the pin in the piston and the fit of the pin in the rod bushing. For my money, the rod caps should be removed and the piston assy. needs to come out. At that point it's a feel thing. What does .0006 - .001 feel like. These are general ballpark numbers but are so slight that measuring ID & OD won't be practical unless you have your Sunnen pin fitting hone with the gauges in the garage.

04-03-2018, 09:32 AM	#3
jhowes Senior Member Join Date: Jul 2010 Location: upstate NY near Mass border Posts: 789	Re: Wrist pins 100IH, What does .0006-.001 feel like? I suspect "feels like no movement at all". So there is no way for the shade-tree mechanic to do this. Jack

04-03-2018, 09:35 AM	#4
jhowes Senior Member Join Date: Jul 2010 Location: upstate NY near Mass border Posts: 789	Re: Wrist pins Sorry about the double post. Jack

04-03-2018, 09:58 AM	#5
100IH Senior Member Join Date: Dec 2011 Location: SW Idaho Posts: 970	Re: Wrist pins No sense of wobble. sideways movement. pin to rod and pin to piston. A fair amount of drag when sliding in or out with light oil. A written description not as good as feeling the real thing and not as good as using the tools that are on the hone.

04-03-2018, 10:51 AM	#6
40 Deluxe Senior Member Join Date: May 2010 Location: now Kuna, Idaho Posts: 3,779	Re: Wrist pins Sponsored Links (Register now to hide all advertisements) The 'feel' of the fit varies with the individual. There is a "palm fit" and a "thumb fit", for example. Next, what is the temperature of the piston when you're checking it? Are you reaming or honing the pin bushings? Lots of variables! As 100IH says, best to let a machine shop measure if you have the slightest doubt.

04-03-2018, 11:13 AM	#7
George Miller Senior Member Join Date: May 2010 Location: NC Posts: 2,975	Re: Wrist pins You would have to take them out. The best way is lessen to your engine before you tear it apart. If it has noise find out which cylinder. Then by sound at different rpms you can tell what it is. I never tear a engine apart with wrong noise going on tell I know what it is.

04-03-2018, 01:08 PM	#8
Kurt in NJ Senior Member Join Date: May 2010 Location: on the Littlefield Posts: 6,159	Re: Wrist pins By rocking the crankshaft and looking for movement, also a finger spanning both surfaces can feel slight movement--- sometimes even watching the oil squish out-- if it squirts out the side it's most likely too loose

04-03-2018, 01:30 PM	#9
Kahuna Senior Member Join Date: May 2010 Location: NorCal Posts: 2,617	Re: Wrist pins With piston & rod removed, when piston is held horizontal, rod should drop slowly.