Auxiliary shaft bearing replacement

rjplenter

rjplenter

True Classic
Since my block was "hot-tanked" to clean it I need to replace the aux. shaft bearings.

I bought a set of pre-sized bearings and they went in reasonably easily, but the shaft requires a little effort (by hand only) to install and then seems to be binding.

The bearings appear to be square but it is very hard to tell. Is there a trick to installing them?

Cheers,

Rob
 
aux bearings

I have to find and check the shop manual.... I think they might need to be align bored. that means a tighter fit into the block and the boring is to bring the bearing into factory specs for the cam.
will check
mikemo90*aol.com
did you know even in the eighties, Ferrari had crank bearing made of brass Babbitt, and had to be shaved to fit the crank??
 
According to my manuals new bearings should be installed by your friendly Fiat dealer

The vendor's listing stated pre-sized, no need to ream.

Maybe someone from MB could chime in with suggestions on how to get them in straight? I can't be the only person who has had this problem...

Cheers,

Rob
 
Hmm, I would have thought, Rob.....

rjplenter said:
....The vendor's listing stated pre-sized, no need to ream......
Click to expand...

....that auxiliary shaft bearing installation on our X's would follow a similar process to "ye olde" in-block camshaft bearing replacements i.e. bearings are pressed into the block (using correct-size mandrels), and then line-bored to a precision fit on the camshaft journal.

Your vendor's statement about "pre-sized" has me kinda puzzled, mate! :confuse2:

cheers, Ian - NZ
 
Aux shaft bearings....

Fiat factory aux shaft bearings were in-fact ream-to-fit. Seriously oversized. I don't know anyone who still has the tools to do it.

Some aftermarket aux shaft bearings available today are pre-sized, not available in any "oversize" like a rod or main, but sized so that a standard diameter aux shaft will slide into it once installed.

Obviously if your aux shaft is out of spec, you'll need to replace the shaft, but these are extremely robust and we rarely see them with any appreciable wear or damage.

The outer bearing is easy to install.

The inner bearing, however, requires a special tool to reach into
the block and push the bearing into position.

Most machine shops don't have race installers that diameter, so
they might have to make the tool that is required.

The only gotcha on the install is ensuring that the oil hole is perfectly aligned with the holes in the block.

-M
 
Non-corrosive hot tanking

is the best answer for this. This type of tank does not destroy the bearing.

Sorry that it is a little late for this suggestion for you, but others may take advantage of it.

Paul Davock
 
"The inner bearing, however, requires a special tool"

Bugger!

I'll have to run over to Applemotors to see if Doug has one. If not maybe he can turn one up on his lathe if I can find suitably sized aluminium or brass stock.

Cheers,

Rob
 
Good work Doug

Since my bearings are supposed to be pre-sized I assume my aux shaft is binding because the bearings aren't yet square.

My plan is to make a tool like this:



The shoulder will be smaller, just enough to engage the edge of the bearing. I figure a soft metal like aluminium or brass will be less likely to damage the edge of the bearing. Then there should be another shoulder the right distance down the drift to engage the large bearing.

Is it possible the original Fiat tool was like this?
 
+10

These aux shaft bearings as delivered FIAT OEM are WAY over sized. After they are installed, they must be reamed/honed to fit with the proper clearance. This is not a matter of assuring the bearings are properly or squarely seated, they are too small for the aux shaft, any aux shaft.

The target aux shaft must be carefully measured with a micrometer to 0.0001" accuracy then the installed bearings must be measured with a precision bore gauge, clearance calculated and bearing reamed/honed as required.

These bearings are quite robust and usually last a very, very long time. They only fail when the bottom end is oil starved, or extremely abused or similar.

If the block is taken apart for tank cleaning, very carefully remove these bearings with full intent to reuse them. During engine assembly, carefully re-install them in their original position.

Bearings may be "pre-sized" but they do crush once installed. This will reduce the bearing clearance post installation to varying degrees.

Proper bearing clearance is very important as excessive bearing clearance can result in low oil pressure.



Bernice


Matt Brannon - Midwest Bayless said:
Fiat factory aux shaft bearings were in-fact ream-to-fit. Seriously oversized. I don't know anyone who still has the tools to do it.

Some aftermarket aux shaft bearings available today are pre-sized, not available in any "oversize" like a rod or main, but sized so that a standard diameter aux shaft will slide into it once installed.

Obviously if your aux shaft is out of spec, you'll need to replace the shaft, but these are extremely robust and we rarely see them with any appreciable wear or damage.

The outer bearing is easy to install.

The inner bearing, however, requires a special tool to reach into
the block and push the bearing into position.

Most machine shops don't have race installers that diameter, so
they might have to make the tool that is required.

The only gotcha on the install is ensuring that the oil hole is perfectly aligned with the holes in the block.

-M
Click to expand...
 
Thanks Bernice

Okay, it looks like I'll be stripping the bottom end again (just installed it) and taking the block and shaft to a machine shop for proper fitting.
 
What happens if you loosen the aux shaft cover?

I had one that would bind when the cover was tightened - does your's turn okay if you just loosen the cover bolts? Mine must have just been a misaligned gasket but I took it apart and looked at it a couple times before I got it right.
 
No cover installed yet

Careful measurement reveals the bearings aren't pre-sized. There is no clearance so they will have to be machined.

Sighhhhhhhhhhhhhhhhhhh.........................
 
Dang. Sorry for your woes.

I left the original bearings alone. They didn't look have any appreciable wear marks, and without being aware of the line-reaming, they still looked like a PITA to install properly regardless.
 
Rob,

your going to have fun finding someone who can ream down a blind hole... for something like a SBC cam bearings you line bore right thru... the Fiat aux shaft doesn't...

I have sized bearings, in 0.000 and 0.0010, so if the shaft is worn it can be ground to size, no need to buy a new aux shaft.

SteveC
 
Might be an option

Thanks Steve,

I just spoke with the guys at my machine shop and they say they think they can do it.

They got the block scrupulously clean but I didn't realise it would ruin the bearings. They are quite pitted and knowing this is the first "stop" from the oil pump to the rest of the engine I knew they needed to be replaced.

I'll strip the crank etc. out tonight and drop the block off tomorrow and keep my fingers crossed.

Cheers,

Rob
 
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