AC Delco reman optispark dissection - Chevy Impala SS Forum
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post #1 of 27 (permalink) Old 06-26-2018, 07:08 PM Thread Starter
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AC Delco reman optispark dissection

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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post #2 of 27 (permalink) Old 06-26-2018, 07:55 PM
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At least it confirms the "remans" have the Mitsubishi sensor....repaired or otherwise.

\'96 BBB 383/T-56
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post #3 of 27 (permalink) Old 06-27-2018, 10:44 PM Thread Starter
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Ordered some bearings today.
Hopefully will have 2 self-rebuilt OEM optisparks in short order.
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post #4 of 27 (permalink) Old 06-28-2018, 06:41 AM
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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.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!
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post #5 of 27 (permalink) Old 06-28-2018, 09:06 AM
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Quote:
Originally Posted by babywag View Post
...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.

Mike - '94 BBB SS (RIP 06/16) - '95 DGGM SS - '96 DCM SS - '92 BBB Wagon
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post #6 of 27 (permalink) Old 06-28-2018, 10:28 AM Thread Starter
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Quote:
Originally Posted by threeimpalas View Post
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-bear...scounts-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.

Last edited by babywag; 06-28-2018 at 05:23 PM.
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post #7 of 27 (permalink) Old 06-28-2018, 07:00 PM
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Quote:
Originally Posted by babywag View Post
......................
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.

\'96SS SOB: SSRI, Herter Tune, Tri-Y II, , 3000 Edge, F/HO bars, METCO extendeds with CV MMC, Bilsteins, currently Vredestein Ultrac Sessanta (315/35 rear). Finally, wait for it... LT-4 knock module!
\'96FWB BUW-Butt Ugly White: PCMPerformance tune, HDFA w/ swissed filter, 1/2 SLP s.s. catback with H- and Flow Super 50s, oem opti rebuilt 3 times, SS Bars, METCO LCA, Airlift 1000, Monroe SS, PowerTrax No-Slip, CTS wheels with +1 rubber. Finally, yes again... LT-4 knock module!

Last edited by 96 Black; 06-28-2018 at 08:23 PM.
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post #8 of 27 (permalink) Old 06-28-2018, 09:30 PM
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Quote:
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It's an oddball bearing. Actually 17mm x 35mm x 9mm, with 30mm steps on it.
Are you sure the 35mm portion isn't just pressed on to the outer race of the bearing? It appears to be a different color than the race.

Mike - '94 BBB SS (RIP 06/16) - '95 DGGM SS - '96 DCM SS - '92 BBB Wagon
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post #9 of 27 (permalink) Old 06-28-2018, 11:36 PM Thread Starter
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Quote:
Originally Posted by threeimpalas View Post
Are you sure the 35mm portion isn't just pressed on to the outer race of the bearing? It appears to be a different color than the race.
Yes, I am sure. Itís 35mm and machined down to 30mm on each side.
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post #10 of 27 (permalink) Old 06-29-2018, 12:21 PM Thread Starter
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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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