Con-rod shell bearings - Alfa Romeo Forum
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Con-rod shell bearings

I'm after new shell bearings for my old 145 T/Spark (1.8)

ALL the old shells (across all four con-rods are original 1998 Alfa, out of the factory), marked with the part number 7646454 but the parts man at my local Alfa dealer says this number has been superseded.

He's offering me four sets (in pukka AR shrink-wrapped blister packs) each of which contains 2 identical looking shells but with 2 different numbers in there. One is marked 55209624 B520 and the other is 55217519 B520 2J.

These new shells have a red mark on the edge. My old ones have no marks at all.


Are the new parts the best available replacement for my old ones?

If so, why do the new parts have different part numbers? The 55209624 is slightly whiter than the 55217519... but that might just be coincidence.

If the shells fit in a certain way (all my old ones - top one seems to get more wear) which one is the top shell and which shell goes at the bottom?


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The shells fit so that the anti-rotation tabs fits into the cut outs on con-rod and end cap respectively. Not known for there to be a top and bottom but that's a good question that needs further research. When I rebuilt my 33 engine there were two grades of shells available for the same size e.g. standard, but one number was for a regular tolerance and the other was for a tighter tolerance, I went for the closer and that engine was still running 140 000 miles later.
Looked it up for the TS in GTVs, the 1.8 engine details are as follows:-

Class A (red) i.d. of con rod half bearings/mm = 50.835 to 50.855
Class A (red) diameter of con rod journals/mm = 50.799 to 50.805.
Same as for 2.0 TS.
Clearance for 1.8 is, in mm, 0.026 to 0.056.
For 2.0, 0.03 to 0.056 mm.

Assembly states "House the half bearings on the con rod caps.......the safety notch towards the same side as the corresponding notch on the connecting rod big end". No mention of a difference between the shells/half bearings.
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Last edited by armoore; 31-10-17 at 08:59.
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(Post Link) post #3 of 7 Old 31-10-17 Thread Starter
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Yes, the old shells are all identically numbered, so (as logical) you'd expect them to fit either top or bottom.

But it's curious that each new pair (the "pair" of shells also has its own separate part number - I'll dig it out) contains 2 "different" numbered shells... although apart from the colouration, they appear to be identical.

Shells with red marks is the thinnest standard size available according to ePer. I got the ePer part number for the "pair" from the Fiat Forum but it's an old one. The new shell "pair" has a different number now and as above, each of the individual shells also has a different number to original... so I'm nervous.

The old and new shells seem to be the same thickness though. I bought a secondhand con-rod from Poland.. (to get hold of the rocking horse poo piston for the 1.8 that was attached to it.... although I eventually later tracked down a brand new Mahle... ) and that had shells which were visibly thicker than my old ones. So, I'm fairly confident... but looking for some reassurance from anyone who can decipher ePer and has the latest version..


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Last edited by Ralf S.; 31-10-17 at 09:16.
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Tricky one this! I have found that those shells are used in quite number of Fiat and Alfa engines including the 1.9 diesels. So I wonder if there is a difference in numbers because of that. Sets (complete) shown by various bearing suppliers do not show a difference but that could be that the images are generic.
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55209624 comes out as a number from GM.
552096240 comes out as GM and Fiat.
55217519 as a Fiat number.
552175190 as Fiat, Cadillac and Suzuki.

Shared diesel engines.
Curiouser and curiouser.
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Last edited by armoore; 31-10-17 at 10:08.
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(Post Link) post #6 of 7 Old 01-11-17 Thread Starter
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Quote:
Originally Posted by armoore View Post
55209624 comes out as a number from GM.
552096240 comes out as GM and Fiat.
55217519 as a Fiat number.
552175190 as Fiat, Cadillac and Suzuki.

Shared diesel engines.
Curiouser and curiouser.
Yes, I've seen the same. The individual new part numbers come up as applicable for Alfa 145 .. and the part number for the "paired set" also comes out as for Alfa 145... but the dealer is similarly not 100% sure so it's made me a bit nervous..

Also I can't find any application list where the old part number (as stamped on the parts) 7646454 is shown in the same fitment as either of the new numbers.

Unfortunately, the Fiat Forum ePer only shows the part number for the paired set. It'd be easier if it just showed 7646454 x 8..

I'll have a look at Mahle's part catalogue.. That's usually useful.


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I ran the part numbers through Mahle's on-line catalogue.

#7646454 is equivalent to the Mahle part 007 PS 20486 200
#55209624 and #55217519 are both equivalent to the Mahle part 007 PL 20485 200

This looked a bit boring in one respect.. but at least we (and Mahle) agree that the two different numbered shells in the paired set are actually the same thing.

I checked some more.

The two Mahle parts are made from the same material ("M114") and have the same 50.787 ~ 50.805mm shaft dimensions. The other dimensions listed are also all the same between the two items.

I then noticed that 007 PS 20486 200 is "No longer available"... and the equivalent part is 007 PL 20485 200.

So, it looks like the new Alfa parts I got are the equivalent of the old ones (and even Mahle, who may be the actual manufacturers anyway) also backs this up/has a matching idea about it... so Proper Job!

Thanks Armoore for having a delve into this for us..

The Mahle catalogue (seems one of the better ones out there) is at:

https://catalog.mahle-aftermarket.co...31592&eid=3306


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