knocking. collapsed piston maybe?

[bigblock]

alright, this is the 93 im fixing up. due to a broken elbow i haven't been able to work on it i a while, but now im back and twisting wrenches again. the engine had a light knock (heavy on cold start ups). first thought, rod bearings right? well i just got done replacing those today. they were gone for sure (pics tomorrow). well that had to be the knock right?? wrong. and btw i checked the crank for any damage and took my time with this job. it took me 7hrs with the help from a lift. (i know im slow but i wanted to be sure) none were spun and the crank was fine. anyways, i primed the system, started her up and the knock was still there as strong as ever. well at least we know its not rod bearings...

so i had my buddy chris listen to the car (pro mechanic) he thought it might be a collapsed piston. and that would be a possibility because when i bought the car it was overheating and i over heated it again (stupid reason) but that didnt make it worse so.. well i took an extension and listened in on the valve covers and various other stuff. on most places its sounded the same except the fuel rails, i could hear it better there . i also pulled the plug wires one by one to see if there was any difference. none.

i have 2 used but good cam chain tensioners. i think those will be the next thing i try. i also have a new timing belt and tensioner im going to try.
i don't thing its crank cancer, the car is almost rust free but i wont rule it out.

so i really dont know right now. the knock is loudest at 2500 rpm but at idle you can barely hear it with the hood down. it has tons of power. feel as good as my 90.

over heating: i think i just need a new radiator now. i replaced the thermostat today (motorcraft oem) that helped but it still was too hot. basically it just to the car longer to get hot. the other one has a bunch of rust and corrosion so im sure it failed. but i think its safe to say all that crap is in my rad plugging it up.

i'll have pics of the rod bearing tomorrow (just because). and a vid of the engine for you guys to listen to.

thanks for any advice you can give

BB

 

[SeanMc]

Timing belt tensioner?

 

[techi14]

betcha its the timing belt tensioner like the above post!

 

[projectSHO89]

If any of those rod bearings showed evidence of anything more than mild scuffing or wear, ie, spun, the con rod is toast and new bearings can't fix the problem.

Never heard of a "collapsed" piston...

Steve

 

[Phoenix]

Did you measure the rod bearings clearance? If the crank had a regrind .....

Video of it would be nice.

 

[jelloslug]

What's a "collapsed piston"?

 

[hawkeye18]

Not only have I never heard of pistons getting collapsed on this engine, I have certainly never heard of messing up a conn rod. I would have to say that the point where the conn rod gets messed up is the same point where the piston forcefully exits the engine (SuperHO, I'm talkin' to you here).

 

[projectSHO89]

Not only have I never heard of pistons getting collapsed on this engine, I have certainly never heard of messing up a conn rod. I would have to say that the point where the conn rod gets messed up is the same point where the piston forcefully exits the engine (SuperHO, I'm talkin' to you here).

When a rod bearing spins, it distorts the con rod so even a new bearing can no longer be held in proper relation to the crankshaft journal.

That's why the bell tolled for my 89.

Steve

 

[hawkeye18]

hmm... I guess you do learn something every day. Time for forged conn rods!

 

[bigblock]

If any of those rod bearings showed evidence of anything more than mild scuffing or wear, ie, spun, the con rod is toast and new bearings can't fix the problem.

Never heard of a "collapsed" piston...

Steve

no none of the bearings were spun. they needed replacing for sure (some copper showing) but i have seen worse pic from here where shos have survived.

collapsed piston: "A piston whose skirt diameter has been reduced due to heat and the forces imposed upon it during service in the engine." now the only reason i considered that was because the car over heated and that can cause one. but i had my friend dusty listen to the car (he has built and re-built many engines. from little 4cylinders to 454 600hp monsters) and he thinks one of the valve shims came out of place or there really loose. he said if it was a collapsed piston there would be 2 knocks 1 when the piston is at the top of the stroke and one at the bottom. this is a single knock and go's with the valve timing. so i'll be pulling the cam covers off soon and doing all that stuff.


heres the pic of the bearing job:





left=front of engine. bottom bearings are the rod cap bearings.

i'll have the vids soon. there uploading.

oh btw i noticed my fan is not coming on at all. bet that an added factor to the over heating lol.

 

[yamahaSHO]

hmm... I guess you do learn something every day. Time for forged conn rods!

Yes, rods on these cars become distorted EVERY time a bearing is spun. In addition, the stock rods are already forged.

 

[SASHO91]

Were any of the rod caps hard to remove?

 

[bigblock]

nope, most of them i could just wiggle out. 2 i had to lightly tap the rubber mallet to break loose. (wooden handle on the rod stud while i lightly hit the other side with the hammer seen in the pic). ok so you tube is being dumb and wont let me upload so im trying photo bucket.

 

[bigblock]

vids: http://s10.photobucket.com/albums/a114/mastabeef/?action=view&current=93sho011.flv

sorry but the other vid when im driving really doesn't have much. you cant hear anything from inside the car so no point in uploading it.

 

[SASHO91]

Don't think it's anything internal... I've never heard a bad t-belt tensioner first hand (just videos), but if I had to pin it on something, that would be it.