Engine knock (with video)

[SaltyDog]

SHO Folks,

I ask for your thoughts/comments/ideas on the origin of, and possible remedy for, this knock/clatter:
https://www.youtube.com/watch?v=G61i8IRU3-g

Note how the knock becomes much less pronounced when #4 plug is removed.

Background: I've only had the car a month, and I knew going into it that the engine had issues. This is an excerpt of what I learned about the car - I found it on line, it is an ad for the car two owners ago:

The car has 173K miles, but just 3,000 miles since going through the motor--heads were removed, valve job, valve seals, cam seals, couple guides, light surfacing were all done. Valves were adjusted to middle of clearance specs. Ford head gaskets were used. The block got a lite bottle hone and all pistons had new Ford rings installed. New intake and exhaust gaskets, new timing belt and crank position sensor. Water pump also recently replaced along with idle air control valve. The rod bearings were replaced along with checking the main bearings. They were all retorqued with a Snap-On digital torque wrench. The engine is making a rattling noise on top which may be the timing belt tensioner and I have the part on order and will be installing it. I've installed the tensioner now and the noise remains. I've driven this car for several years and the noise has not affected how the engine runs, and it seems to go away about 2,000 rpm or so. The engine is basically rebuilt and all rod and main bearings reinspected and all within spec.

Here's what I've done so far:

- Verified that all valve clearances are w/in spec
- Verified cam timing is correct
- Checked vacuum with a gauge, vacuum was steady...I think it would fluctuate if a valve was leaking, perhaps?
- Verified Timing belt is installed correctly
- Verified cam chain tensioners are OK (noise comes from other end of engine anyway...)
- Used stethoscope to positively "hear" the knock coming from cylinder 4...it is distinct.
- Changed #1 and #4 rods bearings. The old ones looked good...crankshaft looked good...I was hoping it would be the answer. It wasn't. :-(
- Engine does not smoke or miss...it actually runs pretty good as far as I can tell - although, I haven't run it hard for fear that parts might emerge from inside the engine.

My thought is a wrist pin......what do you think?

Thanks in advance.

Brian

 

[yamahaSHO]

Sounds exactly like the car I bought with a spun rod bearing. The noise was the piston hitting the head.

 

[SHOdded]

The sound is in Horrific Definition. Hurt me to watch the video all the way through.

Rod bearings, a good investment.

http://rcmautomotive.com/id19.html
http://www.rockauto.com/catalog/x,carcode,1138968,parttype,5212
http://www.shosource.com/catalog/product_info.php?products_id=256

 

[rubydist]

it sounds exactly like every SHO motor with a bad rod bearing that I have ever heard.

Since the SHO motor typically trashes either #5 or #2 rod bearing first, I am guessing that you didn't change the one(s) that really need changing.

I would pull the pan again, pull the caps off #2 and #5 to see what they look like. Make sure the crank doesn't have any scratches. If the bearing has spun, you must put in a different crank or regrind yours, and you must replace that rod - both will be damaged from the spun bearing.

You are right not to run it like that - it is only a matter of (a short) time until parts emerge from the side of the block, given its current condition. However, if all that top end work has really been done, its easily worth saving.

 

[Toolman]

Any particular reason you did not change all rod bearings?
Did you plastigauge the ones you did replace? What did the old ones you removed look like?

 

[sperold]

I had a 86 Taurus wagon years ago that had either a piston slap or a wrist pin noise that was quite a bit like the sound on your audio. If it is any consolation, I put about 100,000 miles on mine without incident.
I am always nervous when dealing with a motor that has been apart and "rebuilt". If you go under and look at the bottom end of your engine again, take a look to see that all the rods (and subsequently pistons) are facing the way they were designed. The piston pin has about a 2 degree offset built into-it, that is there to prevent piston slap (mainly). If it is in backwards, it is guaranteed to make a noise.
It is a longshot... but then again having that noise for the last 4-years without any problems, deserves a look at everything possible.

 

[SaltyDog]

Appreciate the feedback so far - thanks!

Toolman - The local parts store only had two sets of bearings, and from the stethoscope work, the spark plug trick and simple listening while the engine is running, it seems like #4 is the source of the hammering.

The old bearings (1 & 4) looked fine, no adverse wear patterns. I checked the other rod bearings - again, nothing abnormal as far as I can tell. All are torqued correctly. Tolerances were w/in spec.

Sperold - Piston in backward? Very interesting....

The block also has a casting issue where it pukes oil out the hole where the lower bolt for the A/C belt tensioner mounts to the engine. I've managed to stem the oil leak by making my own set of gaskets, but it is a jury-rig at best. I'm thinking I need to go with a new short block. Projects....