Let's rebuild a 350 (maybe), PT.1

[C-10 simplex]

Basically, what happened with this 350 is that cyl#4's exhaust valve somehow got in contact with the piston and actually broke off and imbeded itself in the piston; Before taking the head off, i noticed that the pushrod for #4's exhaust rocker was bent and the rocker was loose. This prompted me to take off the head to investigate further:





#4 piston:


Also, if it makes a difference, cyls 2 and 6 were full of oil and probably a mixture of oil and water:


What originally happened was that the engine started to run funny----the vacuum gauge swung wildly in pulse with the engine and the engine would stall out under 900 rpms.

So, this prompted me to take the engine out and put in on a "test stand." The last time i tried to run the engine, i added more water to the radiator, but then water started to come out of the dipstick tube(there was apparently a small hole in the tube):



This, then prompted me to take the rocker covers off which led to one "gruesome" discovery after another with the exhaust valve etc.

Water came out of the pan like so after the oil drained out:


The reason for the orangeish color is not due to rust----this is the new Dex-cool extended coolant.

i'm trying to be practical here and decide to rebuild or get a new, reman(or even used) engine.

So, please list all the possible reasons for the above AND in the order of likely hood.

P.S. i took this head off 4 yrs ago to replace head gasket (which turned out to be unessesary due to mis-diagnosis of another problem) i don't remember if i used sealant on the head bolts, but i could possibly find out soon by looking at the books i used.

[C-10 simplex]

1) i looked at the head bolts and yes, all of them have some sealant on them; So, i feel that there is at least a 50% chance this was not the problem.

2) i also read that EGR intakes are prone to cracking. This engine has always had the factory iron egr quadrajet manifold that i love.

a) Does water flow thru the manifold? i'm ASSuming it does?

b) Any tips on how to check the manifold for cracks?

[swamp rat]

A crack in the block or heads or manafold is possible, but i'm pretty convinced that if cyl's 2 and 6 had oil and water in them and that you previously removed the head for a "miss diagnised" problem then the problem IS a failed head gasket and intake manafold gasket or both, and also a possibility the head bolts didn't seal adding to the problem..

Did you re torque the head bolts after you put the head back on and it was run for a bit? did you recheck the intake manafold bolts again after it was run?? Did you put thread sealant on the intake manafold bolts that pass into the heads water jackets? if not tho's issues could cause a major leak which would fill the cylindars and crank case and also explane the vacume bouncing allover the place.

As for why one valve failed its hard to say, if the timing was off i would think more of the valves would have contacted the pistons, or more pushrods would be bent so i'd rule that out. Is it possible you didn't have the pushrod properly adjusted or didn't have it properly in the lifter cup and rocker when you reinstalled it? its the only thing i can come up with along with the possibility bad lifter but a bad lifter wouldn't cause a broken valve.

Yes water flows into the intake on a 350 (assuming its what you have)

Now because you imbedded the valve head into the piston that piston is shot and needs to be replaced, that cannot be accomplished properly without a full rebuild with proper machining of the crank and block and now the heads by a machine shop followed by all new pistons, rings, valve job ect....

To be honest i think you should take the thing to a shop and let them rebuild it for you or buy a allready rebuilt engine because your "miss diagnised problem" and subsequent repair work is probably the root cause for the failure.. probably why there is a lack of response by other members here in 4 days. Good luck!

EDIT: I just wanted to add that i'm not trying to be harsh with you or discourage you in any way cause we all have to learn sometime, but i think if you want to proceed with a rebuild you need some guideance from an experianced mechanic and not a book because there is just too much that a book won't cover.

[C-10 simplex]

1) No, i did not re-torque any of the head bolts after running it for a while; i now read that you're supposed to do that.

Didn't check any of the manifold bolts either.

i can't say with 100% certainty that i put sealant on the head bolts, BUT upon inspection, there appears to be some sort of sealant on all the bolts AND if the books said to use it (i used 3 books), then i very probably DID use sealant on all the bolts.

a) engine "lasted" about 4000 miles after the head got put back on.


2) The "mis-diagnosis" was that white smoke was coming out of the right side exhaust pipe only----i have true duals. So, i thought it "must" be the right side head gasket. It turned out to be the vacuum modulator on the trans----this was discovered by sheer luck as the tube from the modulator to the intake fell off during a test drive and the smoking immediately stopped. i also noticed that the trans would not shift past 2nd gear. On quadrajet manifolds the vac modulator tube plugs into the right side of the manifold, thus trans fluid was being burned by cyls on the right side of the engine etc. etc........

3) As far as the valve, do you think maybe cyl #4 filled up with water and the hydroliced taking the exhaust valve with it? i'm "pretty sure" i adjusted the rocker(s) right before putting the valve cover back on.

a) why can't the piston simply be "cleaned up" and run as is? When i say "imbedded" i meant that when i took the head off i noticed that the head of the valve was stuck to the top of the cylinder---sort of like i coin on it's side. But i was able to remove it with my hands. You can probably see the vertical scuff mark in the pic----posted a better picture, previous one was incorrect.

[swamp rat]

>>>The engine "lasted" about 4000 miles after the head got put back on.<<<

That still leads me to beleve the gaskets failed.

>>> As far as the valve, do you think maybe cyl #4 filled up with water and the hydroliced taking the exhaust valve with it? i'm "pretty sure" i adjusted the rocker(s) right before putting the valve cover back on.<<<

No, the cylinder cant hydraulic with the valve open and the valve had to be open in order for the piston to hit it and break it. i beleve the problem can be isolated to the install of the push rod, adjustment or rocker and lifter. Or the only other possibility i can come up with is the valve got stuck open momentarily and the piston hit it possibly cracking it at the stem, have you ever reved the engine so hard you floated the valves?

>>>why can't the piston simply be "cleaned up" and run as is? When i say "imbedded" i meant that when i took the head off i noticed that the head of the valve was stuck to the top of the cylinder---sort of like i coin on it's side. But i was able to remove it with my hands. You can probably see the vertical scuff mark in the pic----posted a better picture, previous one was incorrect.<<<

Its risky at best, If there is any indent or melting in the top of the piston i wouldn't do it, if it can be rubbed off with a little scotch brite and your fingers then its not bad. It was hard to tell with the picture posted, if the piston looks to have been compromised structurally i wouldn't run it, i don't think it will last and cause problems down the road.. That said maybe you can get someone to have a look at it for there opinion? Oh if you do take a little scotch brite to it you need to turn the engine over to move the piston to the top of the block surface and be really carfull not to get any if the stuff down the side of the piston


[/QUOTE]

[C-10 simplex]

The only time i revved the engine above 3500 was when i was doing some 1/4 testing and that was only once and it was about 6 months before the engine started acting funny.

a) i'm probably leaning towards improper installation/adjustment of #4's exhaust rocker/lifter also, but just as an outside possibility, i noticed that in the very first picture every valve spring top(not sure of the proper name) has oil on it EXCEPT for #4 exhaust. What's the possibility that the valve got starved of oil and got stuck in the open position thus causing the piston to strike it?


2) What i was trying to get at as far as "cleaning up" and trying to re-use the piston was i could see why now maybe this particular, #4 piston might need to be replaced, but why would all of the pistons need to be replaced/ crank and block machined/heads rebuilt etc. if it's just this one piston?

[dmwphoto]

time for a long block

[mongoose]

just wack it harder with a hammer... you shouldn't need to turn the motor over at all to get the crank out...

just pop off all the caps.. keep them in order, yank out the crank.. just be carefull not to nick the crank.. if it's still good. get a long bar.. just wack away, if it wont move, hit the head of the piston to break the ring land.. as that piston is junk imo and not worth keeping.


that isn't a new crack you can see it in the first picture.. pound the piston out the top..

[Ticker]

Um...you can take it apart for fun...but it's way scrap

[C-10 simplex]

Nevermind; i got #4 out: It came out easier than i expected.

However, i have some new questions:

First off, all the pistons came out pretty straightforward---there was no significant ridge at the top of any cylinder.

But piston #1 is different from the other 6 good pistons in that the rod is very tight on the wrist pin; Requires considerable effort by hand to pivot it and i can't get it to "float" (right term?) at all on the pin. Whereas all the other 6 "good" pistons pivot and float very freely---the rods just flop to one side when you put them down. Also, i noticed that piston #1 does not seem to have much, if any, oil in that pin area as compared to the other pistons.

What does this mean? i couldn't find anything on this phenomenon in the books.





Piston #4 also has this condition, but i would expect that as #4 is junk anyways.

[dmwphoto]

clearly there is an issue with that piston/wrist pin. I would have the block miked to be sure the cylinder wall is no overly worn.

[Ticker]

Keep in mind that the pin is pressed into the rod and floats in the piston in a stock 350. This is referred to as a "pressed" vs. "full-floating" (floats in a bushing in the rod) pin.

A pressed pin shouldn't rotate in the rod, and if the pin won't move easily in the piston then it's likely galled or the pin is bent. #4 had the valve impact, right? So..the sudden stop probably bent the pin.

Regardless, it's scrap.

[C-10 simplex]

i meant pin rotating/floating in the piston

But i think maybe i got a little ahead of myself: The engine is now basically completely disasembled. i understand it's basically scrap and all---i'm just wanting to investigate out of curiosity and to hopefully prevent such a disaster again.

Maybe an interesting twist?:

After i took the timing gear and chain off(the engine was upside down at this point), i rotated the cam and #4 exhaust lifter fell out. Whereas before it was "stuck."

The cam turned in the block no problems and #4 exhaust lobe seems ok:



i also took apart #4 exhaust lifter and it too "seems" ok, not that i know what to look for because i've never really taken a lifter apart and the books don't really get into detail about this aspect:



This lifter also seemed to move up and down in it's bore after i got the engine turned right side up and was turning the cam by hand. i also tried the lifter in other bores and it also seemed ok.

Given what we now know, what do you think caused this catastrophe?
NOTE: i haven't really looked at the head yet.

[Ticker]

No worries Root cause is likely the same - bent pin.

The books don't go into lifter diagnosis because it's not typically done - they're cheap and not rebuildable, and usually if there's a failure it's on the lifter/cam interface and obvious.

I agree the cam looks fine; what does the bottom of the lifter look like?

There's nothing to positively retain the lifter, i.e. it can move up and down freely in the lifter bore. It's retained in the bore by the spring pressure through the rocker and pushrod.

I suspect that the root cause of the failure was a broken valve and the heads will tell the story, specifically inspection of the broken valve and the condition of the guide.

[C-10 simplex]

Originally Posted by Ticker

No worries Root cause is likely the same - bent pin.

The books don't go into lifter diagnosis because it's not typically done - they're cheap and not rebuildable, and usually if there's a failure it's on the lifter/cam interface and obvious.

I agree the cam looks fine; what does the bottom of the lifter look like?

There's nothing to positively retain the lifter, i.e. it can move up and down freely in the lifter bore. It's retained in the bore by the spring pressure through the rocker and pushrod.

I suspect that the root cause of the failure was a broken valve and the heads will tell the story, specifically inspection of the broken valve and the condition of the guide.

1) Nothing unusual---the bottom looks like the other 15 lifters, which i'm ASSuming are ok. Can provide picture(s) later.

2) Re: heads. Will report back in a few days as my schedule has become a little hectic lately.