2000 K3500 454/7.4 runs rough; sucks and blows

[Motrhedx81]

I have a weird issue with the 454 in my 2000 GMC K3500. I've been racking my brain for a long time. When I watch it idle at the tail pipes it will suck a rag in and out on the right bank, but not the left bank (left seems to run fine). It acts just like what's happening in the video linked below. I've had it for a little over a year and did a lot of work when I got it. It has about 195k miles.

Rebuilt the heads (3 angle valve job, decked, new seals)
New Bosch 19lb injectors
New pressure regulator
New distributor, plugs, wires, coil
New O2 sensors
New fuel pump and filter
New coolant temp sensor
Cleaned MAF and IAC
Gutted catalytic converters (one was broken up already)
True dual exhaust (helped I'd which bank the issue is on)

Compression test was all around 150 psi before I did all the work. Leak down was pretty bad, which led me to do the heads, but I haven't rerun the leak down yet.

Engine doesn't smoke at all (that I've seen). It does run a little rich (I can smell it). Makes sense that it would if the the O2 sensor is reading extra oxygen from the sucking. I did run an infrared temp gauge/sensor on the manifolds one time and the right bank was not getting as hot or consistent as the left.

It runs good, relatively speaking, except for this weird issue. I'm down to thinking bad lifters or bad cam. Bad valve springs are a possibility but unlikely, I think, due to having the heads rebuilt. I would think a bad timing chain would cause issues on both sides.

Any thoughts? Has anyone seen this before? I posted to this video but never got a response to what the end resolution was.

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[454cid]

Very interesting video. I just had my valve covers off and didn't notice a broken spring, but didn't really look either. I do have fuel getting into my oil, and assume I have an injector or 8 leaking.

I wish I could have seen better what he was seeing on that gauge he was using.

I also have the blown out lower intake gasket.... the truck has always had it.

The exhaust sucking a rag in, is not something I've seen or heard of before.

Unfortunately, I don't have anything to add.

 

[Erik the Awful]

I believe I've heard of using a rag on the tailpipe to find a bad valve, but it's been a few decades.

 

[Schurkey]

You NEED the leakdown test. A scan tool may also be helpful if you look at the misfire history to see which if any cylinders have misfire problems.

Wild Guess: One or more valves not seating. Perhaps due to improper valve/valve seat machining, wiped guide, concentricity problems, etc. MORE likely due to excess lifter preload. The preload is so tight the valve can't close.

That often leads to wiped cams. Deal with this SOON before something gets genuinely damaged.

 

[DerekTheGreat]

The original 350 in my '89 would suck a rag up the tail pipe, blow it back out and then suck it back in again. Something was going on with cylinder #1, it would foul the spark plug pretty regular. I assumed it had burnt the exhaust valve up and so I had another engine put in it. I did not think to check the things Schurkey mentioned, but it was a turd engine anyway, burned a quart of oil with every tank of gas.

 

[Motrhedx81]

Bump... any other thoughts?