My 454 Rebuild

[Schurkey]

4. Do some quickie diagnosis. Blunt eight small nails and dab a little silicone dielectric grease on 'em, slide them between the plug wires and the distributor boots, so that you can feel the metal plug wire ends with the nails. Start engine, touch a grounded jumper wire to each nail in turn. Does the knocking stop when you short-out the spark to a certain cylinder?

You must be registered for see images attach

Remove serpentine belt, start engine. Maybe the knocking is from the A/C compressor, or the PS pump or some other accessory.

INSPECT FLEXPLATE.

Cranking compression pressure test. Maybe cylinder leakdown test. Poke a borescope down each spark-plug hole while you have the plugs out anyway. You say oil pressure didn't change, and it still runs good. That's helpful.

 

[Spareparts]

Unfortunately i can't do anything till late friday or saturday then the wife will have a new (used) truck and i can start driving her old truck.

 

[Spareparts]

Messing with it today doing the cylinder drop test i can't really isolate the noise but it is odd.
Seems almost like piston slap the way its acting. Noticeable cold, almost gone warm, no noise hot. I think i have a collapsed piston that has just gotten worse.
Changed oil today and did not see anything unusual. Just normal 3k used oil with no glitter and nothing on the drain plug magnet.
I also took out the regular AcDelco plugs that were gapped at .045 to NGK Iridium with stock .060 gap.

This all started with subpar work i accepted from the machine shop because i just needed to get the engine replaced.
So now im trying to make a decision.
Trade it off for a newer suburban 2005/7 ish with a LS engine and just newer all around. I figure my suburban and 5K should get a pretty decent one. Of course i would need to fix it up and change replace stuff on it as needed or wanted.
Or, Keep mine and rebuild another engine over the winter starting with a GM Performance 454 bare block. When done i would be into it around 6K for what i want but all new with aluminum heads. It would still be a 1998 suburban though. Transmission and Tcase are good, suspension is all rebuilt, No rust or dents other than miner door dings. If it was not for the engine i would be working on interior as thats the last thing i can/need fix.
Hard choice!

 

[OutlawDrifter]

Messing with it today doing the cylinder drop test i can't really isolate the noise but it is odd.
Seems almost like piston slap the way its acting. Noticeable cold, almost gone warm, no noise hot. I think i have a collapsed piston that has just gotten worse.
Changed oil today and did not see anything unusual. Just normal 3k used oil with no glitter and nothing on the drain plug magnet.
I also took out the regular AcDelco plugs that were gapped at .045 to NGK Iridium with stock .060 gap.

This all started with subpar work i accepted from the machine shop because i just needed to get the engine replaced.
So now im trying to make a decision.
Trade it off for a newer suburban 2005/7 ish with a LS engine and just newer all around. I figure my suburban and 5K should get a pretty decent one. Of course i would need to fix it up and change replace stuff on it as needed or wanted.
Or, Keep mine and rebuild another engine over the winter starting with a GM Performance 454 bare block. When done i would be into it around 6K for what i want but all new with aluminum heads. It would still be a 1998 suburban though. Transmission and Tcase are good, suspension is all rebuilt, No rust or dents other than miner door dings. If it was not for the engine i would be working on interior as thats the last thing i can/need fix.
Hard choice!

New to you rig = starting over with someone elses vehicle they are getting rid of. Newer GMT800/900 rigs have less 2nd row leg room. If you're hunting the LS, just pull the 454 and put a 6.0l in your 'burb.

I understand that once you have a bad taste in your mouth about a vehicle, its hard to look past, even when it's fixed. I chased a vibration in a 1989 K5 Jimmy that only had 58k miles on it, sold it with 65k, and never did get the vibration completely gone.

For as much time and effort you have put into your Suburban, I say fix it and keep it going.

 

[South VA]

Messing with it today doing the cylinder drop test i can't really isolate the noise but it is odd.
Seems almost like piston slap the way its acting. Noticeable cold, almost gone warm, no noise hot. I think i have a collapsed piston that has just gotten worse.
Changed oil today and did not see anything unusual. Just normal 3k used oil with no glitter and nothing on the drain plug magnet.
I also took out the regular AcDelco plugs that were gapped at .045 to NGK Iridium with stock .060 gap.

This all started with subpar work i accepted from the machine shop because i just needed to get the engine replaced.
So now im trying to make a decision.
Trade it off for a newer suburban 2005/7 ish with a LS engine and just newer all around. I figure my suburban and 5K should get a pretty decent one. Of course i would need to fix it up and change replace stuff on it as needed or wanted.
Or, Keep mine and rebuild another engine over the winter starting with a GM Performance 454 bare block. When done i would be into it around 6K for what i want but all new with aluminum heads. It would still be a 1998 suburban though. Transmission and Tcase are good, suspension is all rebuilt, No rust or dents other than miner door dings. If it was not for the engine i would be working on interior as thats the last thing i can/need fix.
Hard choice!

Man, do I get that. More than once I've thought about selling what I have and moving on to something that appears to be better, or is at least reasonably capable of being better. That is a hard choice you have there.

But of course I'm biased, so take the following with that in mind.

Personally, I love this platform because it ticks all of my automotive boxes: it is utilitarian, mechanically capable, pleasant to drive or ride in, aesthetically pleasing, and normally pretty reliable.

To state the obvious, if it's a newer version, well, it's a newer version. Not a GMT400. I guess it depends on how into this platform you are.

I think I know which way I'd go, were I in your shoes; but of course I really don't.

OutlawDrifter summed it up nicely:

New to you rig = starting over with someone elses vehicle they are getting rid of. Newer GMT800/900 rigs have less 2nd row leg room. If you're hunting the LS, just pull the 454 and put a 6.0l in your 'burb.

I understand that once you have a bad taste in your mouth about a vehicle, its hard to look past, even when it's fixed. I chased a vibration in a 1989 K5 Jimmy that only had 58k miles on it, sold it with 65k, and never did get the vibration completely gone.

For as much time and effort you have put into your Suburban, I say fix it and keep it going.

FWIW, that's where I landed with my '96.

Good luck with your decision.

 

[Spareparts]

For being a 1998 other then the engine it is about as perfect as you gonna find mechanically.

 

[Spareparts]

I'm pretty sure the engine will go till next spring so I'm really thinking of doing another engine but using a well known in spokane machine shop to check things over before any assembly. Then putting the parts in I request to my satisfaction.
And taking everyone here along for the ride!

 

[Reluctanse]

A "newer" burb like you propose is going to be pushing 20 years old at this point... and need all the same repairs and maintenance you've already been through, plus added complexities of canbus and body computers, and a host of problems associated.
Stay the course my friend! Build the 454 "right" the way you want. Worth it in the end...

 

[Spareparts]

Kinda my thinking also @Reluctanse

 

[Road Trip]

I'm pretty sure the engine will go till next spring so I'm really thinking of doing another engine but using a well known in spokane machine shop to check things over before any assembly. Then putting the parts in I request to my satisfaction.
And taking everyone here along for the ride!

As a fellow GMT400 big block owner, over here in upstate NY I am really feeling your pain
& frustration concerning this (to date) Bad Actor 454.

Since you mentioned that your original engine was smooth, but the new engine was
never as smooth...so obviously you aren't chasing a phantom issue. In other words,
this specific engine bay** was (and still is?) capable of supporting a smoothly running L29.

And so far no joy, but *not* due to lack of trying. You have alternated between black box
and 0411. You have had gone to the trouble to verifying the fuel injectors all flowed the
same. Several passes at the ignition system. Used a temp gun on the cats, then went on
to measure the actual exhaust back pressure. Fuel pressure checks. Been capturing/sharing
data with a scan tool. Etc., etc.

****

Man i aint got enough energy for all that! Hats off to you!
I may not be to bright or methodical but i am tenacious.

I'm not the disagreeable type, but in this I beg to differ.

Anyone swapping between the black box <> 0411 box more than once for t-shooting
purposes, or checking for equal spark on all 8 individual wires, I'm thinking that you are
working at a pretty high level. And I think we need to upgrade you from tenacious to this:

You must be registered for see images attach

(Compliment, BTW)

And me? I don't mind a problem...but I *hate* a mystery. So, IF you go ahead & persist
with fixing this, I would like to offer the following remote support:

* I have a known-good, smooth-running '99 L29. It is currently still running off of the
original black box that the truck was built with. IF you would like one or more items
cross-checked in my engine bay for proper operation I will cheerfully do this. (ie: Giving
you what we used to call "known-good, flown good" parts to troubleshoot with --
considered 'better than new'. (!)

* Our current problem definition is a rough-running misfire that defies diagnosis. This
to me has the feel of test procedures / test equipment that has insufficient resolution
for narrowing this misfire down. But I don't know for sure. Therefore, although I still
don't know where I am finally going to end up with for troubleshooting tools, I'm thinking
that for now I'll get the same/similar tools as you and see what kind of misfire counts that I
get over here under my hood, and then we can compare. (ie: Just how clean/misfire-free
can a '99-spec 454 run on today's 90/10 gas/corn diet?)

Are we looking more carefully at how these big blocks run than 99% of the folks still
using them? (I don't *think* so?) At any rate, I really want to understand all this *before*
it happens to me, so it only makes sense to get involved from a purely selfish standpoint. :0)
And not if, but when we figure all this out it will be good data for others down the road.

Got a few other ideas, but the main point of this is that IF you decide to start fresh &
really put this to bed once & for all, I will be happy to assist in any way I can, up to and
including using my own truck to try to replicate what you are seeing.

What can I say? We troubleshooters have to stick together, through thick & thin...

:0)

**aka: "Power Barn" (courtesy @ralmo94 - I like that!)