My 454 Rebuild

[Spareparts]

You think you're stumped!
As a last try i just ordered 2 new springs but knowing my shipping times they will not be here by the weekend so next weekend i'll change em.
You can be D4MN sure i will take this one apart and discover the problem.
No totally forgot to just remove the belt and will do this weekend.

 

[Road Trip]

That is my thought also but the bearings were not that great either with plenty of copper showing and unfortunately i sold the block as i do not have room to store an engine.

Copy that. I completely understand the lack of room/inability to hold onto decommissioned engines.
I'm currently fighting the space issue myself. :-(

 

[Road Trip]

BTW here is a pic of the plugs i changed out last weekend after maybe 3 weeks running.

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The plug color(s) look faultless, showing just the barest light tan coloring. The #7 plug
looks the same as all the others. With these modern EFI engines the
plugs don't color nearly as much/as quickly as the old carbureted/mechanically
choked when cold motors.

There does seem to be some random black spots on the insulators? And there's
that black line of spots on the #2 spark plug? This would make me a bit curious if
you are seeing any knock sensor counts? But at the same time weren't you having
issues with your software not being able to obtain knock counts from the stock
black box?

At any rate, everything looks to be near identical in all 8 holes per the plugs.

* No signs of oil getting past the rings or valve stem seals.
* No signs of abnormal fueling in any cylinders. (no leaking injectors, etc.)
* And you are seeing a steady 19" of vacuum at idle. (Good)
* You were getting pretty good gas mileage. (12.5mpg?) (Good)

There's a lot that is going right inside this engine. Just the fact that
it runs the same on both the original black box and the 0411 eliminates
a lot outside of the engine. And you have methodically been able to eliminate
just about everything else except the valve springs. And as long as the
valve guides are tight & the seats are good, installing a couple of known-good
springs into #7 is the next step in the process of elimination.

In all my years I only had one other engine that was this hard to sort out...but
I *did* finally figure it out. Looking back, I'm glad I didn't just take the easy out
and avoided the temptation to burn it to the ground. :0)

Will be watching this channel for breaking news. God speed, Spareparts --

 

[Spareparts]

The thing should be running like a million bucks.
It does not use a noticeable amount of oil. Always on the full mark.
I have not checked vacuum for a while but last checked yes it was a steady 19.
Fuel mileage running around town with AC on mostly between 13 and 13.5. Highway with AC on at 70MPH is 14.5 with AC off i would imagine at least 15.
Yeah, with the 0411 and original black box it ran the same. I replaced the black box with a different black box ECU programmed with the GM stock tune for my truck. No change.
I have replaced every sensor that was a store brand or questionable with AcDelco or Delphi. No change. New distributor made no real change.
New cap and rotor helped slightly but misfire still there.
It's like everything i try helps slightly but really nothing changes.
Im pretty much down to the valve springs. IF new springs fixes it great! i don't need to build a new engine this winter. I suspect they will fix nothing but killing a couple hours time, But.
Springs are the last thing i can try and when they don't fix it the dead last option is pulling the heads. Im not gonna waste the time to do that. I'll just do up a new engine this winter using some choice parts that i should have done in the first place and a different "reputable" machine shop.

 

[Spareparts]

Amazing, Valve springs arrived today sooner than expected aaaaaand they're the wrong ones.
The only ones available that would be here by Saturday i could find were from Auto Zone. They are supposed to be delivered by Saturday. Melling VS-2259. Fingered crossed.
The wrong ones i ordered are for a 5.3LS. No idea how i did that but i did.

 

[Piratehunter]

@Spareparts what application or scanner are you using to monitor and report the misfires per cylinder.

 

[Spareparts]

well 3 different ones depending on what im doing.
Just driving around to work and such Torque Pro. Verify what im seeing with Torque i use a Solus pro scanner sometimes. Playing with tuning i use HP Tuners scanner/logger.
All read pretty much the same for misfires.

 

[Spareparts]

Have not mentioned much about it the last week or so but interesting things i think.
The piston slap? seems to have all but disappeared. Only hear very slight when cold now. Also seems to be running smoother than ever but it still has the #7 misfires but not as bad. Don't know what to make of it.
Correct Valve springs arrived so ill be changing them Friday or Sunday and see what that does. Probably nothing but it's a easy troubleshooting step.

 

[L31MaxExpress]

Have not mentioned much about it the last week or so but interesting things i think.
The piston slap? seems to have all but disappeared. Only hear very slight when cold now. Also seems to be running smoother than ever but it still has the #7 misfires but not as bad. Don't know what to make of it.
Correct Valve springs arrived so ill be changing them Friday or Sunday and see what that does. Probably nothing but it's a easy troubleshooting step.

My L31 383 is continuously logging cylinder 4 misfire and after a good bit of troubleshooting and an engine running as smooth as silk at 2,000 rpm it was logging a steady count of misfire that would seem to indicate a completely dead cylinder. That being said I did a power balance test at both idle and 2,000 rpm. Killing each injector cut the same RPM off all 8 cylinders. In the end I disabled misfire monitoring, and I am not going to mess with it further until I pull the cam, lifters and intake manifold. I only axed the monitoring because it is causing the PCM to unlock the torque converter at random times.

 

[Spareparts]

Cruzing along at 25 mph mine feels as smooth as silk also. As soon as i give it the throttle i can feel it missing but mine will not log any misfires above about 900 rpm, never has.
If i try a higher idle say 700 rpm the misfire is highlighted and feels a lot worse.
If im driving say 45 mph and give it any throttle i can feel the misfire.
Cylinder drop test feels about the same on all cylinders at idle in park. I never thought to try it at 2k rpm under load but now i really wanna do that.
Im going to change the springs on #7 and will do a log from cold start to hot showing misfire for all cylinders. I strongly suspect this will not fix it either.