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Discussion Starter #1
I was told this is a genuine AC Delco reman.
It looks the part, but I am not 100% sure on this. Feel free to verify or what not.

Came off a running engine, but when tested the distributor will not hold vacuum.
Testing w/ both vacuum & low air pressure revealed it's leaking badly from bearing area.
The bearing has no play, but pretty rough, doesn't feel good spinning.
I am going to try and replace the bearing.
See if I can make a good unit out of it.

On with the pics.
Here is the disassembled unit laid out. Was very clean inside, and hardly any wear on cam drive.



Here is how they indexed the rotor to shaft



Here is the Mitsubishu optical sensor, appears to have been reworked/repaired.



Here's the wheel, notice the rub marks. It seems flimsy compared to the other OEM opti wheels I've got from other units. Different # as well.



And last the bad bearing. Nothing comes up with a search on this part# 6903RS. But from research others report bearing #SX0389LUACS25 works.



Anyone else taken a recent AC Delco reman apart?
 

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Discussion Starter #3
Ordered some bearings today.
Hopefully will have 2 self-rebuilt OEM optisparks in short order.
 

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I tried tracking down the bearing with your info. Can you forward the supplier / number details? I have a 2-year old aftermarket opti the prev owner installed that I had rebuild with parts from an old oem unit and new tuneup parts. Still get P0336 code. I want to rebuild that old dist. out of my first FWB and a new bearing is the only missing link. I'm gonna take some real good measurements to see if that aftermarket unit has been clocked wrong all along. At least I can trust the original is right.



Post up hints when you R&R the bearing eh.
 

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...And last the bad bearing. Nothing comes up with a search on this part# 6903RS...
That is a standard designation for a bearing. Any bearing that fulfills that type (deep-groove ball), size (17mm ID x 30mm OD x 7mm Thick), seal (contact seals), and internal clearance (standard) would work. Timken, Koyo, SKF, NTN, etc. would all manufacture such bearings. It should be pretty easy to obtain.
 

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Discussion Starter #6 (Edited)
That is a standard designation for a bearing. Any bearing that fulfills that type (deep-groove ball), size (17mm ID x 30mm OD x 7mm Thick), seal (contact seals), and internal clearance (standard) would work. Timken, Koyo, SKF, NTN, etc. would all manufacture such bearings. It should be pretty easy to obtain.
It's an oddball bearing. Actually 17mm x 35mm x 9mm, with 30mm steps on it.
Care will need to be take to get the height correct when pressed back together!
Searched high & low, only place I found that had one...
https://bearingsdirect.com/ball-bearings/metric-sizes-ball-bearing/6900-series-thin-speed-duty/sx0389luacs25-ball-bearing-17x35x7mm-sealed-see-discounts-inside
Their description states it's a custom size...
They're just north of me in CA, so should get them quickly?
Here's some pics to show how it differs from a standard bearing.

OD


The steps...OD


From what I found/read the new replacement only has one step vs. the 2 of the OE style bearing, but will work. The step is where the hold down retainer rests on bearing. Other end goes into distributor housing so doesn't "need" the step.

Bearing removed...


Homemade dealio I made to help with removing the bearing. Just used a c-clamp & a socket that fit on shaft to press it off.
 

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......................
Here's some pics to show how it differs from a standard bearing.

Ok.


Ok.


Thanks. Just ordered 2. John Hurt:// "Why buy one when you can get two for only twice the price?" // Figure I'll give the other one away in <6 months anyway.
 

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Discussion Starter #10
So, I believe I figured out why it was leaking so badly, absolutely no way it would have ever held vacuum.
The housing isn't a smooth machined surface for the bearing.
It was kind of sudo staked into position leaving many gaps for air to leak.



This will need to be addressed/fixed when the new bearing is installed. Or it'll continue to not hold a vacuum.
The opening is larger than it should be for a 35mm bearing. Too big to be an interference fit.
Only thing I can think of is to loctite the thing in there?
Obviously, don't want it to spin anyway.

I can see why few people do this, correct bearing isn't available, fit issues, sealing issues, etc.
If I had spent hundreds of dollars on this thing, I'd be very annoyed, to say the least.

Anybody out there got a recent reman ACDelco they can vacuum test?
I'd venture a guess if it's like this one, it won't hold any vacuum @ all.
 

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Discussion Starter #11
So new bearings showed up today.
You can see the difference, 2mm thinner and no step on one side.



Couple ways to skin this cat...
Press bearing onto rotor 2mm less
Get a 2mm spacer made(or find washer?) for rotor so that it cannot be pressed on too far.
 

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You can use Loctite Bearing Retainer if you choose.
Do a search and you will find it. Used it for years in the machine maint. field.
Never tried to pull a vacuum but it never leaked fluids when I used it.
 

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Discussion Starter #13 (Edited)
You can use Loctite Bearing Retainer if you choose.
Do a search and you will find it. Used it for years in the machine maint. field.
Never tried to pull a vacuum but it never leaked fluids when I used it.
Any recommendations on which one? A search came up with ~6 different ones.
609, 660, 645, 635, 620, 640
The bearing fit is pretty loose in housing.
This one seems a logical candidate but I’ve got no experience with using stuff.
https://www.henkel-adhesives.com/us/en/product/retaining-compounds/loctite_660_automotiveaftermarketonly.html

Yesterday after a failed attempt, I was able to successfully make a spacer.
Drilling out a washer, then final cleanup and finish with dremel.
~21mm OD, 17mm ID, and ~1.95mm thick



Last issue is retainer, seems both ears are cracked. Can be seen w/ naked eye.
Have to weld it up, if not happy after will just need to make a new one.

So took 2nd one apart, OEM w/ bad bearing, bearing is made by NTN Japan.
Bearing fell right out housing, definitely NOT an interference/press fit.
This one held vacuum. So appears it's the housing that's the problem w/ the other one.

Take a look @ pic, reman housing has a small groove on bottom, OEM one does not. Reman is cast, OEM is machined.
So if I use the OEM housing probably do NOT need to seal it up/loctite??

 

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gap fill

https://www.grainger.com/category/retaining-compounds/threadlockers-and-gasket-sealants/adhesives-sealants-and-tape/ecatalog/N-1bnr?cm_sp=Product_Details-_-Categories_Based_on_Your_Search-_-IDPPLACAT

This Grainger link has the retainers and specs.
You would choose the one best suited by temp. and gap fill needed. Also if it will be disassembled often there are varying strengths.
the 660 looks good for up to a .02 gap fill.
620 is .015 gap fill and high strength.
Others range down to .006 and more. Depends on the housing to bearing gap if any and or the finish. You mentioned a rough finish on one of the housings (cast or machined).
Some require a primer so be aware of that.
648 looks like a good choice to use. .006 and no primer. If you need any force to install the bearing this should be fine.
 

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Discussion Starter #15
One down, one to go...

Bearing pressed onto rotor, installed height using my 2mm spacer is good.



Assembled using the OEM housing, did NOT seal bearing to housing. It does hold a vacuum. New MSD cap & rotor, should be good as new?



Not sure when I'll get around to installing it? Supposed to be pretty toasty next few days, and working on the car isn't going to happen when it's 90-100* outside!
 

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Quote: I was able to successfully make a spacer.
Drilling out a washer, then final cleanup and finish with dremel.
~21mm OD, 17mm ID, and ~1.95mm thick



Just to clarify, was it completely homemade from plate, or did you just mod an existing washer? I'm finding as you probably did it's not a slamdunk finding a plug-in spacer. With little of the right tools I'm thinking just a couple of little hold-offs superglued temporary in the seat. Would you agree there's room to get under there to remove them after the bearing is seated?


BTW thanks tons for the write-up so far.
 

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Discussion Starter #17 (Edited)
Yeah searched parts stores, hardware store, struck out.

Modded a washer that was close OD & thickness.
Drilled out inner and dremel to get the ID correct.
PITA
I’m guessing height needs to be correct for optical sensor & disc.

Also received a reply from NTN, they stopped producing the bearing 2001. So whoever the reman/aftermarket folks are using for bearings isn’t NTN.
Somebody out there is making the bearing, need to find a part# & who.
 

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Discussion Starter #18
So finally an update for those who asked.
It's been so hot forever just never felt like working on it.

The aftermarket opti I had installed has just been getting worse so finally had enough.
Intermittent misfiring @ high rpm is annoying as hell!
It lasted a couple years before acting up, but gets the thumbs down!
For the record it's an AZ Duralast Gold rebranded Spectra Premium.

My DIY refurb is installed, fired on 1st turn of key and seems to run fine.
Already 80* outside again, so called it quits on finishing reassembly today.

 

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Posts 1 & 6 detail the bearing. No mods to housing needed, just a 2mm spacer washer to properly seat. Weather's gettin' nicer and looking to see if this redo does it. Full steam ahead Mr. -wag!
 
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