Intake Side of Valvetrain Totaled...Why?

[RyanTSi]

Okay guys (and gals, I know there are some out there ) Been gone from the forums for awhile, the Navy decided it would be good to send my squadron to Alaska However before I left I pulled my head off to get a exhman stud extracted and a valve job. Well, while I'm on Ice Planet Hoth, I get a call from my wife saying the the shop suggests just getting another one, talking like $1200 in damage.
I talk to 'em and it sounds like I jumped time (most likely) and I'm just gonna go all in and grab me a 2.0L Stage I longblock from SBR and rebuild the other one (the head casting is still good). But heres the thing, they were as confused as I was as to how this happened, especially since other than a leaking exhman, the car ran GREAT before the pull.
When I went to pick it up today, here is what I found...
EVERY valve on the intake side is bent slightly (by slightly I mean you need to look close to see it),
ALL of the intake valve guides are cracked on the piston side,
All the cam lobes are scored on the "actuate" (push down) side, and none of them scored the same.
They also said that alot of the lifters were broken, but I haven't found the ones that are yet, I haven't inspected all of them either.
I'm thinking one of two things, running a couple teeth off for a long period of time, or somehow the carbon build up on the pistons had accumulated to the point it was messing with clearance. Theres alot of buildup in the piston faces, and I haven't messed with the timing since Ive had it. Sorry for the long post, but I don't want to forget anything, I'm posting here since this forum gets alot more "look time". If you want to see pics, let me know. Thanks in advance,
Ryan

 

[Old Mitsu Tech]

I would say you jumped timing on the intake cam. Either cam can become out of sync with the crank and bend valves. This can happen from one of usually 2 or 3 reasons. Bad or old belt, improper tensioner adjustment or worn out adjuster, or oil on belt with a combination of the others. Usually the engine likes to destroy the exhaust valves. Now, if it spins out at the crank end, it will go after whoever is the closest whether it's the exhaust or intake valves. This is a little less common but it is certainly possible. I recently bought a 90 awd eclipse and it had the valves bent. I pulled the oil fill cap and had some one crank over and the cam didn't move plus the engine had a whiny nasal wheeeeee sound which is lack of compression. No need to break out the gauge here. I would chance a guess that the collateral damage is from the impact damage on the valves. The lifters is kinda rare as far as what I have experienced with these. Cam scoring could be possible lack of lube or such. I would definitely have all the galleys purged and cleaned just to be sure. I did have an engine with some foreign debris in the cam galley and it wreaked havoc. How it got there I haven't a clue. It was just there. I don't think carbon buildup would do it unless it was a tremendous amount. I mean tremendous. I would definitely put a new auto tensioner in when going back together. Cutting a corner here is a kiss of death. I hope this helps. I can also tell you how to adjust the tensioner without that damn feeler gauge technique Mitsubishi is so fond of. My head is too large to go between the engine and body. Let me know

 

[RyanTSi]

Here ya go. The circled areas are the intake side, drivers side, the rest of the lobes look the same but like I said, only on the actuate side. the head is already cleaned and tanked. These pics are from before I took it in. I didnt even notice it, but looking at the pics, you can see it plain as day!

Crap. The head is none too pretty. Im quite interested to get a good look at the ring lands as well as the faces once I clean them off. Im sure there will be rough areas/potential hot spots on them, but I dont know what to expect with the rest. Either way, its coming out and slowly being rebuilt as the new motor will be coming soon. The fella I talked to said the late model 93's were 7-bolts, which I dont doubt, but I have a six-bolt oilpan... Are the head bolts on a six bolt 12mm or 11mm? Mine are 12... just trying to clear it up.

The big question here is I know it was an off timing problem, but how the hell was this puppy still running? I know the 4g63 is tough...but that tough? Come on....

Ryan

 

[ddavisaf]

If the timing was not off which is possible, then the problem was actually a warped head.
However, you would have been able to tell in either case.
If it was the timing, you would have heard the knocking as the scours are not small.
If it were a case of a warped head, you more than likely would have been experiencing headgasket problems.

 

[Defiant]

The head didn't take a ride in the back of a pickup face-down, did it? Show us the valves.

 

[RyanTSi]

The head didn't take a ride in the back of a pickup face-down, did it? Show us the valves.

HAHAHA ....God No. Here are the intake valves, with their silly yellow, yer sh*t is broken paint. I really dont think youll beable to tell by the pics though. They look straight to me, unless I look at it from the top and turn it in circles.

If you meant the scoring could be from riding on its face, every cam lobe is scored like that, in the spot where it contacts the lifters.

Ryan

 

[RyanTSi]

An update, Ive pretty much decided I was running about 2 or 3 teeth off for a long time, and was miles away from destroying myself. The motor is out now. Im still not 100% on what happened, but I bought a Stage I Longblock from SBR to replace the corpse. Now if It would just get here.......

Ryan

Still looking for closure

 

[Defiant]

If that motor was ever turned in reverse when off, it's extremely easy to hop the belt over the intake sprocket. As other threads will show, there can be considerable relaxation of the belt between the cam cogs when stopped.

 

[RyanTSi]

yeah That sounds about right. Very possible. Holy cow this motor is turning out to be a bundle of mystery. Ive had this car for three years. In that three years Ive put a max 3k miles on it. Ivr also replaced the rod bearings. It had 130k on the clock. You saw all the burned up oil on the pistons? Found out why. All of the cross hatcing is still on the cylinders and the piston rings are all nice and shiny, reusable even. They look like I just popped em on myself. I think the motor was rebuilt before, and somebody bored the cylinders and put in the same pistons with oversize rings. Ill have to mic it to be sure though.

Heres the Q. Is that even possible? To put more than 5k on a motor and not seat the rings ?


Ryan

 

[RyanTSi]

Okay, Im only bumping this thread for everyone elses info.

I got my closure, starts awhile back.

So, awhile back I spun a rod bearing. My buddy and I replaced the bearings and re assmbled, called it good, and I drove off.

Add 2k miles Ca. to Wa.

Since then I have pulled the 7 bolt and disassembled.

On the oil pickup tube I find tiny metal fragments.....

In the thrust bearing oil journal, I find the same thing......

scenario:

Bearing spins, fragments disperse, get into lifters (common), screw up lifters, eff up valve clearance, begin to drive intake valves into pistons (verified this on pistons), bend intake valves slightly, driving continues (into pistons), begin cam scoring, scoring fragments chill in head until they.....

Creep down into the end of the oil cycle (turbo), make their way in, plug thrust bearing, turbo howls when nearly warm, when really warm (thinner oil), howling stops, drive for 2k, damage and destroy engine internals like it was the cool thing to do.

Turbo is fine after I rebuilt it, 6 bolt swap almost done, lesson learned.

To all that dont know already, if you spin a bearing, pull the pan, and guess what?

Youre pulling the head and diassasembling it. find the fragments, dont be stupid.

Sorry for the bump, nuff said.

Now look at me and at me....