95 LT-1 Idle Cell Comparison - Humidity?

[spfautsch]

That might be the culprit of the weak spark you had recently.

I think I might have possibly eliminated weak spark as the problem. Read on...

The energy of the ls1 coils is too much for the platinum disks to handle on these plugs and the spark scatters taking the least resistance path around the platinum disk. I should say they are either defective or the ls1 coils are overkill for 41-906s.

Since this is the first time I've ever used a double-platinum plug to check spark strength (normally I use a new + clean champion that I keep in my toolbox for this specific purpose) I 'm going to go out on a limb and say I think these type of spot-welded disk platinum plugs are just junk. I also dug out my old OE plugs that have been run an unknown amount (possibly original to the car) exclusively with the optispark / hei2 setup. This is the plug on top, the plug below is essentially new. Notice how the center electrode is eroded away around the perimeter of the platinum disc. Also, the ground electrode has long since expelled it's platinum.

Tr55s are always better for non stock application, but they must be replaced quite often for optimal performance.

I just wanted something I could get cheap at the local parts house. Since I'll need to order some water pump gaskets from my favorite online parts house I'll probably buy several different exotic plugs (double iridium, ruthenium, ???) to compare. The prices there are almost $4 per plug cheaper than the local wallet sucker parts house.

... and you have a regulator for 60psi, go for it. Much better spay pattern and atomization with the newer ls1 style injectors.

This makes me wonder if there is a OE style 4 bar regulator that's a direct fit for this application. But unfortunately this pressure problem was with the original non-adjustable 3 bar regulator. I'm going to cut it open when all this is over and see what's going on internally, because it seems like the problem could be caused by clogging in the return section. The lines don't seem to be the problem because the new regulator doesn't exhibit this behavior.

Anyway, as I parked it three weeks ago it wouldn't even start without giving it pedal. I wasn't sure what had happened but in my troubleshooting process I noticed I'd left the radiator cap sitting loose so I likely boiled the coolant during my last few test drives. This made me wonder if I'd burned some exhaust valves. So after the plugs and factory injectors made no difference I started out by doing a complete compression check. Every cylinder was within 2 psi, so I breathed a huge sigh of relief.

I then installed my new binary O2s and recalibrated the UEGO, thinking all the while it may be the sixth Tuesday of the month of Never before I get to enjoy the fruits of that labor.

After that I decided to check off a few other remedial things vilefly suggested. Hats off to you sir.

Since it wouldn't run, I flashed a bin with 0 degrees cranking spark advance and had the wife crank her while I observed with a timing light. To my surprise I was never able to see the painted-on timing mark. After confirming by checking the opti outputs with my ignition controller's timing check mode, I found the low res pulse was retarded a massive amount. Seems like when it got hot the loctite "high temperature" sleeve and bearing retainer I used to secure the two parts of the opti hub together got soft enough to allow the hub to slip.



I had assembled this around December of 2018 when I had bought a spare opti base and decided to do some disassembly to discover what rebuild options there were. This is the rebuilt hub that came with the car. I removed the 1/8" roll pin that originally filled the hole because according to my degree wheel it was off by about 6 degrees - 2+ of which was due to my cam needing to be installed advanced to make target ICL.

Anyway, I'm debating putting this back together and re-drilling the hub for another roll pin. That, or looking for an adjustable MSD base I can get cheap off eBay so I won't have to trial-and-error 20+ times to get the junk opti hub installed back at zero like I did back in December 2018 (with the engine comfortably mounted on a stand).

Thinking back along the progression of this problem, it seems highly possible this was the entire cause, and that the opti hub slipped more than once. An initial slip of a few (8-16) degrees of retard would more than explain the difficult cold start, lean readings and rich smell I was describing at the beginning of this thread. Where it's at currently is at least 30-40 crankshaft degrees retarded. I'm surprised it would start at all.