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Old 11-18-2014, 09:04 PM   #1
Marshall V. Daut
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Default Wrist pin holes in connecting rod upper end

I searched the archives for an answer to my question du jours, but no luck. So...
I'm replacing the wrist pin bushings in a friend's engine during an overhaul. The brass bushings I removed had two holes drilled through them in the connecting rod's upper end, one on either side of the center. There is also a hole in the center of the rod and it's slightly larger than the two holes on either side. The bushings I removed were not drilled through in the center hole, i.e., only two oil holes were drilled by a past rebuilder. Shouldn't the middle hole in the connecting rod top part also be drilled out? What other purpose would this center hole serve if not to allow additional oil to enter? It's just a dead hole otherwise.
So, drill it or leave it alone and rely upon the two oil holes on either side? I'm leaning towards drilling it because you can't get enough oil to the wrist pins in my opinion.
Marshall
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Old 11-18-2014, 09:22 PM   #2
James Rogers
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Default Re: Wrist pin holes in connecting rod upper end

Pretty sure the answer is yes but, I can look at the shop tomorrow. I have 8 or 10 sets of new rods in stock.
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Old 11-18-2014, 11:18 PM   #3
Marshall V. Daut
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Default Re: Wrist pin holes in connecting rod upper end

Thanks, James. I can't trust ANYTHING that was done to this poor motor. How about .008" clearance on the exhaust valves? Or the two flywheel dowel pins missing? No front oil slinger behind the LOOSE pulley? NO piston ring end gaps??? ZERO sign that cylinder walls had been honed in the last rebuild? It goes on and on. That's why I can't rely upon only the two holes being drilled into the wrist pin bushings, but not the middle one. I await your reply.
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Old 11-19-2014, 05:28 AM   #4
Marshall V. Daut
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Default Re: Wrist pin holes in connecting rod upper end

"1930 coupe" -
Aha! That would very neatly explain the presence of that center hole, which is now a dead hole with the long one-piece bushing installed. Of course! Now it all makes sense. When the two-piece bushings were in place with the original pistons, that center hole was a pathway for oil to enter between the bushings, while the two outer holes drilled into the two bushings fed oil to each one individually. So, the oil entered through those three holes. With the long one-piece bushing setup in the modern pistons that this engine has, however, that center hole is now blocked by the bushing and appears to be useless. Because the upper part of the connecting rod fed oil to the bushing through those three holes, I believe I will go ahead and drill out the center hole in each rod to replicate this design. What could it hurt? I can't see how the integrity of the bushing will be compromised by the addition of one more small hole drilled through the bushing. And the holes are far enough apart from each other that the bushing material shouldn't shred away between them.
Thank you for what I believe to be the definitive answer to my question.
Marshall
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Old 11-19-2014, 01:30 PM   #5
J and M Machine
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Default Re: Wrist pin holes in connecting rod upper end

These holes that you are mentioning are for alignment purposes when the rod was machined at the factory. Also on some aftermarket rod lathes used these for support.
These don't need to be drilled out as the two holes are sufficient for oiling of the wrist pin.
Flat head Fords also utilize this drilled alignment bosses.
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Old 11-19-2014, 02:44 PM   #6
James Rogers
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Default Re: Wrist pin holes in connecting rod upper end

I looked at a dozen sets of rods today and the holes were drilled in several different patterns. The one thing I did notice was, the holes on the side were NOT drilled on any of them. There were some drilled in both top holes and some drilled in only one top hole. I did have one set with the clips still installed and they were drilled in one hole plus the center top hole, none of the others were drilled in the top hole.
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Old 11-20-2014, 10:01 AM   #7
Marshall V. Daut
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Default Re: Wrist pin holes in connecting rod upper end

Thanks to all, who provided input. Two of the rods had side holes, two didn't. None had center grooves in them for a clip. Dunno whether these mixed rods came from the factory this way or whether some restorer mismatched them. "wouldn't surprise me.
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Old 11-21-2014, 06:43 AM   #8
James Rogers
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Default Re: Wrist pin holes in connecting rod upper end

Marshall, if none had center clips or 2 piece bushings, they are not Ford factory issue and probably are from aftermarket sources. I believe, like you, they are mismatched repro reconditioned probably by garage mechanics that did not check them or didn't know the difference.
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Old 11-21-2014, 12:56 PM   #9
Marshall V. Daut
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Default Re: Wrist pin holes in connecting rod upper end

I misspoke. Two of the rods do have the center groove, two don't. I don't recall if the two rods with grooves have the side holes, or whether it 's the rods without grooves that have the side holes. 'Doesn't matter now, though. Thanks for checking, James.
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Old 12-29-2014, 05:38 PM   #10
bmodeltman
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Default Re: Wrist pin holes in connecting rod upper end

I have the same problem as OP.Supposably rebuilt years ago.Decided to check it out and found it not to be to my stardards.I did find the wrist pin holes in my rods on either side are not drilled out.I`m confused if they should be or not.
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Old 12-29-2014, 06:15 PM   #11
George Miller
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Default Re: Wrist pin holes in connecting rod upper end

I bet those rods are not all the same weight. Sounds like you got your self a mess. Good luck with the engine.
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Old 12-29-2014, 06:44 PM   #12
bmodeltman
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Default Re: Wrist pin holes in connecting rod upper end

I did send the rotating assembly out and had it balanced.Took them apart and found the holes on top of the rods were drilled.Quess I should have looked before asking.
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Old 12-29-2014, 11:20 PM   #13
Ron W
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Default Re: Wrist pin holes in connecting rod upper end

The angle on the three locating points (one top center and two near studs on lower end of rod) should be retained in case future work might be needed. Those three points hold the rod for any machining. Ron W
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