Thanks greywolf, I hope it's not the engine! The plenum is in my sig. Fixed that like over a year ago. I also replaced the #8 injector last year.

 

Swap injectors on six, and eight. See if the problem moves with the injector.

 

Im thinking same thing from clogged cat or previece clogged cat caused from the blown plenum.
Did you change out cat after doing the plenum?
I assume your burning the oil and not leaking it, could be bad valve stem seals.
If you decide to do the heads get good aftermarket replacements.
You can find suggestion for heads on this forum.
If I remember correctly number 8 cyinder is usually the first valve to burn
from the clogged cat, because its the closest to the cat.
This could be your miss on number 8 cylinder.

Dave

 

Tried that....after I
bought a new one..punched myself in the junk for that order

 

Dave, yeah I changed the cat, also it's burning not leaking. I planned on a head from Odessa but was told sticking a reman or new one on there would stress the rest of the motor and do further damage?

 

bull****.
who said that - don't take advice from them.

155 is good for overall.
do a leakdown test (see youtube) and pinpoint your compression leak.
if you can pinpoint a valve, either pull that head for repair or just replace it.
i assume you already replaced cap, rotor, wires, plug, injector on #8.

 

^^^ I guess you have never put nice new heads on a old worn out motor and seen what happens then. Dodge can tolerate it better than other makes but in the long run rings and other parts will fail faster with new heads on a higher mileage lower bottom end. Its like putting new t*** on 50yr old, nice top end and a worn out hole.

 

That sir is probably the best analogy I've heard yet...but I've put new reman heads on an older engine and that engine still runs good today ten years later so I don't really see how it specifically applies.

All of this being said, if you can correctly diagnose whether its seats, stem seals, or what have you, or rings for that matter it would be the difference between a long and short block. Of course stem seals end up being pretty obvious on their own because they tend to smoke quite a bit on overnight start up every single time but clear up after a minute.

At the mileage I would conclude rings myself. But you need to do a leakdown on 8 for sure.

Lastly in my situation, I have never had a cat on the truck, likelyhood I will ever damage the heads is very small. So when it started acting funny on 8 I knew it had to be ignition or fueling, the plug looked ok if not a little glazed so I removed injector 8 for another I had on hand. Problem solved, which lead to all injectors getting replaced, I now have 7 spares Leak down test those cylinders, lets see if it is blowby. I've also seen severe consumption of oil from a bad pcv valve in a multitude of engines I've diagnosed in the last ten years. Pull it out, shake it a bit, if it rattles, generally speaking it's ok, even then they are cheap as hell and if you can't recall ever replacing it now is the time.

 

It does apply, I still get sbc motor (yes sorry chevy) that have skipped a timing tooth, ok bent valves, push rods you know.

Customer; Ok put new heads on it please
Me; Ok how many hrs are on it,
Customer; Don't know.
Me; Not good to put new heads on a used high hr motor.
Customer; Ok so put new heads on it, cheaper lets see what happens

Less than a month this motor was back, blowing smoke. This is just one motor over the many years I have seen this happen to. 90% of the time after putting on new heads the blow by gets worse and soon its needs a rebuild.

As posted the Magnum motor is much better taking new heads, but yes a leak down test would help.

I once thought that same thing never had a cat on my truck ever, no way I can have cracked valve seats, boy was I wrong, I found four when I took the heads off.

This cracked head thing can be fixed/stitched..... once its a one time deal and if it fails its new head time.

http://www.locknstitch.com/RepairExamples.htm

http://www.locknstitch.com/Repair%20...8%20Repair.pdf

 

Never have I seen a set of reman factory heads affect the lower end of the engine's lifespan in 16 years.

Cases were the changing of heads affected things, after the valvetrain destroyed itself or something else (Like a timing belt break, or a bunch of bent push rods and once a collapsed lifter, overheating...) But on engines where the head was simply cracked, seats wore or cracked, guides worn and so on, replacement worked every single time with zero effect to the rest of the engine barring improvement as an effect.

I realize that in many cases where replacing the head is necessary the failure affected the whole motor and that is where your coming from.

But, we can go back and forth all day, a leak down test is what will tell all of us the problem.