How about this flanged bearing?
http://www.vxb.com/F6903ZZ-Flanged-S...-p/f6903zz.htm
F6903ZZ-2.jpg
If not, use the designation "NR" after the bearing number to do a search. 6903 NR, and similar, 6903 zznr, ss6903 nr, etc. I have to tend to the "squab", and keep her out of the bathroom before she develops a killer bacterial weapon in there.
Last edited by vilefly; 02-13-2018 at 05:05 AM. Reason: more info
I'll have to pull the hub back out and will post pics and dimensions. The shoulder is in the middle of the bearing with steps down to the nominal 33mm race size in front and back, so that probably wouldn't work just from eyeballing it. This is another area where GM really screwed the pooch on design - all in the name of saving a quarter of an inch.
The hub is a relatively loose press fit to the shaft and I believe even OE used threadlocker to secure it once aligned to TDC. It's fairly easy to remove by holding the hub with something and tapping the shaft out with a punch - no vise or pullers required. Most of the rebuilders drill a 3/32 hole for a roll pin at the mating line before disassembly so they don't have to re-index the hub. I don't want to attempt to remove the hub from the bearing without a replacement bearing, so that will be at the very bottom of my bucket list.
I'm not feeling like messing around in the garage any more tonight - just finished the 44th oil change (x 10,000 mile interval) and tire rotation on my daily driver, removed the trigger wheel to return the junk distributor base for a refund, and washed the sooty smelling oil off my hands. Going to spend some time relaxing and entertaining my daughter's dog that she swore up and down she was going to take care of. The animal would fetch the tennis ball from 6am to midnight if there was someone willing to throw the damned thing that long.
The results I had with the other trigger wheel seem to show the a similar pattern of timing skew, trending towards +3 degrees between cyls 1 and 8 and zero around cyl 6. The only explanation I can think of for this other than a junk trigger wheel is that my cam gear is slightly elliptical. Without others reproducing this test on different engines I don't really feel alarmed enough to warrant pulling the timing cover and possibly creating a new oil leak. For all we know at this point, a brand new OE timing set might produce more erratic results. And though we're geographically diverse beyond the pale of vision, I don't see a line forming of LT-1 owners wanting to yank their water pumps to attach a degree wheel and find true mechanical TDC to verify. Ultimately my intentions were to upgrade to an electric water pump so I can run a standard double roller timing set, so maybe that will be my excuse to pull the engine next winter.
Last edited by spfautsch; 02-13-2018 at 11:47 PM.
Why don`t you hit the local scrapeyard. There might be some cheap not working units. Anyway you only want the stock gm wheel.
New opti is almost impossible to find. Even GM sells only reman units now.
If we follow common sense you`re timing gear should be a little too tight. Since you hit alot of *5s at idle and stretched chain gives *7s.
Eleptical wheel will produce too many vibration when spun at high rpm.
You can compare chain link counts with crank sprocket tooth counts. If they have 2:1 ratio it is possible that half the chain is busted.
I have a stock 95 opti I can scan if you want when I get back home.Originally Posted by kur4o
The gears have something like 15 and 30 teeth to give a 2:1 ratio but the chain is longer and the links should walk around so they don’t line up regularly.
Mitch
'95 Z28 M6 -Just the odd mod.
'80 350 A3 C3 Corvette - recent addition.
The thought crossed my mind. Generally I go to <big auction site> when I'm looking for scrapyard parts since most yards list stuff there and it saves me the agony of using the telephone and a bunch of driving. I'm not seeing any salvaged optis there. Just one MSD that in the description says it was setting a CMP code so probably needs a new sensor and the MSDs use a proprietary sensor.
But in addition to wanting the correct wheel I'd like a new bearing, and I'm not hopeful of finding a source for one.
If the timing gear wasn't perfectly circular or bore where the cam seats in the gear isn't perfectly centered that would cause the chain to be tighter for half a revolution.
Thinking about this, I've almost worked up the courage to pull the timing cover and see what I find. Maybe I'll put a double roller chain in temporarily and re-test timing. If the cloyes set I put in last year is egg shaped it would really burn me because if memory serves that was a very expensive set.
vilefly might appreciate it.
Found a double roller billet timing set (w/o water pump drive) for a very reasonable price so it's on the way.
If it improves or eliminates the timing skew I guess I'll take that last step off the cliff and buy an electric water pump.
Will try to post pics and measurements of opti bearing and base tonight. From extensive reading I'm not feeling very confident an alternative will be possible. I'd really like to remove the hub from the remanned delphi unit to see if there are any part #s visible on it. But I'd also like to be able to return it as it isn't worth what I paid just to gain a better quality trigger wheel.
BTW vilefly the metal shielded bearing type you posted a pic of would be a problem for vented optis because they need to hold vacuum. The vent system might suck the grease out of that one not to mention letting unmetered air into the intake.
Are the stock ones sealed at the back then ? Otherwise they’d suffer the same. I’ll open mine up when I get back, it’s been a few years now since I was inside.
Mitch
'95 Z28 M6 -Just the odd mod.
'80 350 A3 C3 Corvette - recent addition.
The bearing grease seals are what make them "airtight". Obviously this is less than optimal, but the distributor really doesn't need to hold much of a vacuum. The amount of air the check valves allow the intake to pull through it is fairly small. But if the inlet hose clogs or gets pinched it could put the opti under full intake vacuum and I would imagine that could cause problems.
Last edited by spfautsch; 02-14-2018 at 12:59 AM.
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