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JPG AUSTRALIA 
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 Topic: Slotted / non slotted shells
Posted: 24 Jan 2024 at 7:55am |
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Trying to refresh myself on the slotted conrod replacement bearings for the 426,which is what i have to install ,cant find the info. Can anyone help? The new rod bolts i have to use are nos ones from awhile back as well,mid 80s but i havent got paperwork to go with them either.
The shells the dealer sent me are all slotted,only the top half shell should be ,correct?
Thanks
Edited by JPG AUSTRALIA - 24 Jan 2024 at 8:25am
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NEVER green
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Posted: 24 Jan 2024 at 8:16am |
On the mains both halves should be slotted so the rods get constant oil pressure.
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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JPG AUSTRALIA
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Posted: 24 Jan 2024 at 8:24am |
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Just talking about rod bearings,ill edit my post
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Alvin M
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Posted: 24 Jan 2024 at 9:01am |
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Only the top need to but some brg companys sent both slotted
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DrAllis
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Posted: 24 Jan 2024 at 9:04am |
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Conn rods are to be turned 180 degrees when using slotted bearings in old engines.
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I M Fedup
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Posted: 24 Jan 2024 at 9:36am |
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My memory on the subject is rather vague. It's been too many years since I last worked on those engines, but it seems to me the slotted bearings were brought into play along with drilled rods for piston cooling jets in higher HP versions. If his rods aren't drilled for that the slots are a moot point. Why would they need to be reversed 180 degrees?
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DrAllis
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Posted: 24 Jan 2024 at 10:16am |
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Because that's what A-C said to do in an official Service Bulletin because they discontinued the old no-slotted rod bearings. Turn the (old style) rods 180 degrees when using slotted bearings.
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I M Fedup
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Posted: 24 Jan 2024 at 10:31am |
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I'm not arguing the point that it should be done. It's more that I haven't seen those bulletins in possibly thirty years, I'm just questioning the "why".
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DrAllis
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Posted: 24 Jan 2024 at 11:02am |
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I'd assume to put the bearings "sweet spot" in the best possible position for longer bearing life when using an old rod that isn't configured exactly like the rifile drilled rod is.
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tbran
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Posted: 24 Jan 2024 at 11:05am |
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The straght up con rods AC used has a greater thrust on one side - this needs to be the side that has the most brg surface. The bulletin was put out just after the slotted brgs went into replacement with the rifle drilled rods.
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When told "it's not the money,it's the principle", remember, it's always the money..
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JPG AUSTRALIA
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Posted: 24 Jan 2024 at 5:06pm |
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Thanks for the reply’s
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SteveM C/IL
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Posted: 24 Jan 2024 at 6:35pm |
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From the manual....Engines in the S/N range of 70-15255 through 70-22076 were built with the slot away from the camshaft. Lab testing has revealed improved oil film retention is achieved when slot in bearing is on the camshaft side of engine. Engines built this way must have rods rotated during any major engine work.
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HudCo
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Posted: 24 Jan 2024 at 7:45pm |
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how would any one ever know about critial info like that without this forum, and having poeple with experance toknow that because those bullitons dont always show up in the revised service manuals somthing that needs to go to the knowlage base
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JPG AUSTRALIA
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Posted: 24 Jan 2024 at 10:37pm |
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Just got hold of set of nos shells 4025253 which after a lot of searching should be 002 under and not slotted .
Thoughts? Hopefully not too tight! But would save conrod turning
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SteveM C/IL
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Posted: 24 Jan 2024 at 11:45pm |
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If your crank is not 2 under you are asking for trouble. At least plasti gage them. My latest 426 w/ 5000hrs is less than half a thou under on rods.
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injpumpEd
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Posted: 25 Jan 2024 at 7:23am |
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can check clearance, and just use the upper half of the .002 unders, and the std in the caps. It's pretty common mixing .001 or .002 bearing halves in the racing world to get the desired dimensions. Only down fall is buying 2 sets of bearings lol! I think these are sold each shell come to think of it. Now, as mentioned above, your crank may not have enough wear on it to allow even .001" tighter clearance.
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210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!
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JPG AUSTRALIA
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Posted: 25 Jan 2024 at 8:03am |
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Hey Ed, i was seriously thinking of doing that ,not a fan of the slotted type, takes away alot of bearing surface. But doing all this upside down in chassis is a bit hard compard to an out of frame rebuild. I measured crank and it was as new spec still , so I’ve passed on the .002 ones and turned the rods and gone with all slotted. The top shell gets the main workout so that was the one that needs the non slot bearing.
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NEVER green
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Posted: 25 Jan 2024 at 8:30am |
A little late but you could send in your old bearings to Calico Coatings and get their latest space age slippery coating.
Not that expensive.
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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DrAllis
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Posted: 25 Jan 2024 at 9:14am |
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So, does Calico fill in the wear void with their coating ??? or do they fill in the void with OEM bearing materials and then coat the bearing surface ??
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NEVER green
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Posted: 25 Jan 2024 at 9:48am |
 DrAllis wrote:
So, does Calico fill in the wear void with their coating ??? or do they fill in the void with OEM bearing materials and then coat the bearing surface ?? |
Their coatings, I sent in a set of rods and on two halves I could see two of the deepest scratches still showing, otherwise looked like new, cept gray.
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2-8050 1-7080 6080 D-19 modelE & A 7040 R50
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Les Kerf
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Posted: 25 Jan 2024 at 4:49pm |
injpumpEd wrote:
can check clearance, and just use the upper half of the .002 unders, and the std in the caps. It's pretty common mixing .001 or .002 bearing halves in the racing world to get the desired dimensions. Only down fall is buying 2 sets of bearings lol! I think these are sold each shell come to think of it. Now, as mentioned above, your crank may not have enough wear on it to allow even .001" tighter clearance. |
From the pictures in his other post it almost looks as though the bottom half shell could be re-used in a pinch (not quite ready to that myself though  )
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