Started to pull plenium. I can see from the gaskets that I have quite a bit of cross contamination between cylinders. Especially the right side, that runs rich. The attachments show both top and bottom of plenum gaskets Left bank is on left side and so on.

The LT-5 architecture uses a plenum sitting atop Injector Housings. So its a bit of a sandwich w gaskets joining the plenum to the Injector Housings, and then the Injector Housings to the cylinder heads. So far, I have found evidence of oil seepage at the plenum mating area, and subsequently the IH interface to the cylinder heads. The cylinder heads also have PCV vents that are adjacent to the cylinder runners which creates a potential for sucking oil into the chambers. Posting pics of gaskets which present evidence of oil contamination of airflow.

Quick update. Cleaned Injector Housings out. Reaching the point of puting top end back together, But first I literally swabbed the valves to removes carbonized crap from some of them. Not sure why some are clean and others have some carbon built up behind valves. Got new gaskets so soon...

Waiting to hear on results of injector flow testing.

Got the results for the injectors. Not good. Aerators are breaking down and disintegrating basically eliminating any atomization and spray pattern. I had one injector not working at all, while another just streamed fuel into combustion chamber. I’m amazed car ran as well as it did.So now the question is which injectors to replace them with. Aerator for Accel is plastic and breaks down.
The RC Engineering are very expensive at $80/iinjector. I need 16. Ouch!
FIC Delphi (New) $729/ set
Southbay sells rebuilt Multecs at $329/set
Accels are $580 for the set.
Bosch III are the narrow body and won’t fit.

Talk about cascading failure.

Along w recommends from resident gurus here, I’ve decided to replace Accels w set of Delphis from FIC. They shipped them out as a matched set w flow rates documented to within 1%. Wanna thank General Disorder and RBob for their help.
Hope to have them installed and motor ready to fire next week.

Motor is back together w Delphi injectors. Idled fine. Hope to get it off the Quickjacks and take it out if the weather holds next week.

Today was a good day to take the car out for the first time after having put things together. Had the opportunity to do some datalogging.
The FIC injectors are rated at 21.5# while the Accels rate at 21#. So my expectation was to see richer BLMs, but in fact, the BLMs demonstrated an overall lean condition. Next step is to check the spark plugs for confirming evidence of this.
However, one issue that appears to have been resolved is knock counts at cruise. Driving for 20 minutes or so at 1800-2000rpm did not result in additional knock counts, unlike previous. I will start to “bump” timing in this area to determine how much more timing can be used here.

Took car out again today after making adjustment to VE table based off yesterday’s log. Typical, we went from lean to rich, but overall motor felt better. I went to stock timing in the area of the SA table where I was seeing knock. Virtually no knock now. Must be a critical area and its one where the car will spend quite a bit of time when in cruise mode.

Pulled a few plugs today before going off. Attached is pic of #2 cylinder plug before and now. I think u’ll be able to tell which is which.

Posts: 8,615 Re: A tuning tale: BLMs say lean, plugs say richHappy Holidays to everyone. I believe we are getting close to wrapping this up.
I pulled plenum to check out coils, primary and secondary windings. All tested fine. Checked plug wires as well. Fine.
Since the plenum was off, I decided to check it for "flatness". Plenum was warped. Straightedge rocked by about .020". Spoke w Dr. Greekenstein (aka Pete). He told me that most plenums have some warpage to them. Suggested silicone gasket around the ports. I used Blue RTV since it is safe for O2 sensors.
Silicone gasket maker can kill an O2 sensor by contaminating it.
Finished installing plenum and took it out for a spin and logging session.
The difference was pretty clear from idle all the way thru. The BLM split was much tighter now w both right and left sides converging closer. Right was still richer than left but now the diff in BLMs was 124-132 or an average of 130 which is close enough. Idle was much more stable @ 925-950rpm and pulling about 48kPa which is pretty good considering Pete's cams.
Also, no knock counts. So I can start inching SA up a bit to see how close I can "tickle" the knock sensor.
So this wasn't The Silver Bullet. BUT, it was one of the pieces of the puzzle.

To summarize so far:

1. Broken injector, poor spray pattern and deteriorated aerator(s)

2. Oil seepage from crankcase vents into combustion chamber.

3. Warped plenum allowing additional air into fuel flow.

All of this points to areas that we probably take for granted when we have our motors apart. Should add these to the list of things to check when doing a plenum pull. It also goes to prove, before any tuning, its important to verify that all components are operating at nominal levels, otherwise tuning is like a dog chasing its tail.
This also suggest that you verify the datalogging measurements with some good old fashioned "eyes on" the motor. The car was running well. I believe had you driven the car. you would not suspect the issues that have been uncovered. Marc thought the car ran well when he drove it several weeks ago before I started this rehab. But had I brought it to a dyno, I likely would have been disappointed.

The datalog I just recorded shows some additional tweaking needed as expected. But not to the extent previous. I know I'll be re-checking torque on plenum after a few heat cycles.