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

[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.