whats the deal with Aluminum conrod bearings?? Vrs tri metal?

[Angie]

On my 2.8 build the bearings for the conrods are an Aluminum composite. WHY?? what are they good for? i have placed the pistons and rod bearings into the block, but now I am second guessing why they are made from this metal.

Can anyone shed some light on this situation??

thanks

 

[2011Supercab]

Basically the aluminum/tin composite has a higher melting point than copper/lead composite and is environmentally friendlier, and they cost less to make.

https://www.tags.co.za/wp-content/uploads/2018/02/IT01.pdf

 

[Blmpkn]

Google says aluminum bearings offer better embeddability and conformability while the tri metals offer better fatigue strength and hardness.

So.. a farm truck needing a quick in-the-barn rebuild gets aluminum but anything else gets tri metals ideally

 

[Angie]

ok, here is all i needed to read from the article from 2011supercab....

"
For example, for an A-600 (tough
aluminum alloy) the recommended limit is 100 hp per liter. For
a 500-plus hp V8 we would need a copper/lead performance
bearing to be able to handle the load. "

and this ....

"These three layers help achieve a combination of strength,
embedability and surface action. Cast/copper/lead can carry in
excess of 14,000 lbs per square inch of load versus about 7,000
for an aluminum bearing. "


I will be ripping apart this engine again and placing in tri-metal bearings just for peace of mind. thanks guys

 

[franklin2]

I like my little 2.8 v6. But I don't see it making enough power to need anything special with the bearings or anything else. Unless you are planning to run boost of some sort.

 

[ericbphoto]

Cool. This has been an informative thread. I hadn't even heard of the aluminum bearings until now.

 

[Angie]

hi franklin, nope not trying to runs the 11's or anything with this build. Just when i read that a part is not as strong as .... (fill in blank) when compared to what was originally in there ... it makes me question why wouldn't ford use Aluminum bearings from the get go ... if the tri-metal is a stronger system, why take a chance and risk a failure 10,000 miles into a rebuilt motor. more of a un-tested product that i can not see chancing.

cheers

 

[19Walt93]

Good quality stock replacement bearings are fine for most everything, I like Clevites best myself. That's what's in my 13 second Mustang 302 and it buzzes to 6000 rpms.

 

[4x4prepper]

I know they are not going to be sitting in coolant and all that, but, I would wonder if there would be any different kind of chemical reactions between the aluminum and iron block or crankshaft. Especially if it sat for a year or more unused and someone tried to start it without priming the oil pump. I was reading on another forum where someone nuked their rare and sought after Isuzu 1.8L diesel in a Chevette by not priming the oil pump and they took out the bearings.

 

[superj]

Dissimilar metal corrosion happens when there is not something to keep them from touching, like primer or paint, or its an alloy that can touch the other metal

 

[alwaysFlOoReD]

Dissimilar metal corrosion happens when there is not something to keep them from touching, like primer or paint, or its an alloy that can touch the other metal

When in the presence of moisture (h2o)...
Not sure that applies with oil.

 

[rusty ol ranger]

"Cheaper to produce" and "Enviromentally friendly" usually equates to inferior quality

 

[superj]

For sure

 

[Angie]

OK, I have a huge problem now with these bearings ....

The ones that were in the engine were .... CB-723P when i did the number search it was showing a common con bearing for a 2.8 std size .... so the cross order came in as CB-723A std ....

when all 6 were in place bolted to spec, there was this weird slop in the crank. I didn't like this and took 1 cap off the connecting rod. I could place a .020 feeler into the space between the bearing and the crank. so this tells me that these bearings are out .010 ... HUGE differences ....

Called around to parts places in town ... to see if they can tell me more about WTF is going on here ... and can i order new sets ....

Nothing around ... but 1 place said they can bring them in from another town in a week or so .... they say 4 ... so i am not sure if it is 4 sets of 6 or 4 bearings alone .....

One place told me they are having very bad times getting internal engine parts for older engines .... we are screwed people .... hoard your old NOS stuff .....

cheers

 

[AndyB.]

I think a good step would be to mic the journals to see if they’ve been turned down and if you need undersized bearing inserts.

If you want nos bearings, they’re available and not expensive.

https://www.ebay.com/itm/185462564358?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=nLfobrrwTwy&sssrc=2349624&ssuid=d87u9en7TgW&var=&widget_ver=artemis&media=COPY

Plastigage to verify clearances is a good idea. When I did my 2.8 rebuild, I was able to use standard rod bearings, but went with NOS .002 undersized main bearings.