My 3.4 pushrod motor has developed a noise that I thought was an exhaust manifold noise on the #2 cylinder (it sounds like a ratty exhaust noise but with a metalic edge) I knew the manifold on there was warped so I prepped another one and installed it. The ratty sound is now gone but I still have the knock noise. I used a stethascope to listen to the noise and it seemed to be coming from the head area and I do not hear any noise putting the stethascope on the oil pan. I pulled the valve covers to see if I had any loose rocker arms and they were all fine (I had tried listening through the vave covers with a long screw driver and I did not hear any unusual noise inside them). I started pulling plug wires on at a time and driving the car and have traced the noise to the #2 cylinder as it goes away when that wire is pulled. The fact that the noise goes away when pulling the plug wire tells me that it is in the bottom end and not the valve train.
The noise occurs between 2000-3200 rpm with a lite throttle. It is not present below that rpm and goes away above it. I tried changing to 10w-40 oil and there was no change in the noise. I had no metal in the oil that I drained (I ran it through a strainer) and no metal showing in the oil on the dipstick now.
The noise does not have the deep knock of a rod bearing and it seems to be too high an rpm to be a wrist pin noise. The engine is carbed so it is not an injector and it is loud enough to hear outside the car when it is going down the road.
The engine had 47,000 miles on it when I got it. I replaced the cam bearings, timing chain and gears, cam, lifters, springs, retainers and locks, water pump, oil pump and pick-up tube and head gaskets as I gasket matched the heads. I left the bottom end stock as it was very clean inside and had relatively low miles.
Sorry this is so long I just wanted to be thorough.
I have stopped driving the car now that I know it was not the exhaust manifold and I have driven the car about 300-400 miles since it started making the noise.
By the way the car runs strong, oil pressure is 55-60 on the highway 40-50 around town and 28-32 at idle (680-750 rpm).
here is a pic just cause I like it

Any ideas would be aprreciated.
Thanks,
Richey

[This message has been edited by STRATOHACKER (edited 04-04-2004).]

Is it possible that it's a piston slap?

Did you have the heads off and look at the pistons?
I've heard that on some engines if the pistons are installed backwards (or maybe in the wrong bank), the compression will cause the piston to rock back and forth in the bore.

This is totally a wild guess. I'm sure others will comment.

If nothing else... free bump to the top.

(Nice looking engine, BTW.)

[This message has been edited by Raydar (edited 04-04-2004).]

quote Originally posted by Raydar: Is it possible that it's a piston slap? Did you have the heads off and look at the pistons?

The pistons are original and have not been removed. Piston slap is one of he noises I had thought of, but piston slap will go away as the engine warms up and they expand to fill the bores, so I have ruled this out for that reason.
Thanks for the compliment
Richey

If you find out, let me know. This is EXACTLY the symptom I have noticed on my stroked 3.1(0 miles) !!! I have tried everything and I have not put the car on the road out of the same concerns as you....

I pulled the motor and tore it back down and found nothing....I did not look at the bottom end, though....I too could not hear anything on the bottom side...

quote Originally posted by Cplensdorf: If you find out, let me know. This is EXACTLY the symptom I have noticed on my stroked 3.1(0 miles) !!! I have tried everything and I have not put the car on the road out of the same concerns as you.... I pulled the motor and tore it back down and found nothing....I did not look at the bottom end, though....I too could not hear anything on the bottom side...

I am leaning toward it being the rod bearing on the #2 cylinder on mine as it is isolatable to that cylinder alone and is more prevalent under a slight load. I will probably end up pulling the pan and checkng the clearances on the rod bearings which I should have done in the first place. I may get lucky and be able to replace the rod bearings and get rid of the noise before it becomes catastrophic.
Richey

ttt

ug - wow this sounds familear....
I have this too. It was alot worse. I had a worn bearing. It wasn't spun, just worn. I still have a light knocking, but its tougher to hear. I did the same thing, pull spark plug wires untill it went away, that told me which bearing to do. I think I may have another one to do. The knock is alot less noticable now, but still there. And also, I could hear my bearing knock in the pan with a stethescope.
BTW - NICE looking motor!

quote Originally posted by Pyrthian: I could hear my bearing knock in the pan with a stethescope. BTW - NICE looking motor!

This is what is puzzling to me I can not hear anything in the pan with the stethescope I hear it mostly near the exhaust port on the head.
thanks for the compliment by the way.
Richey

sticky exaust valve could be a possibility

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I have run both compression and leak down tests and all is well with that so I do not think I have a valve sticking and the noise goes away when pulling the #2 plug wire at the cap and driving the car. If it were valve related I believe it would make noise all the time. I am leaning toward it being the wrist pin do to the location of the sound and the fact that it is a higher pitched noise than what I have know to be typical for a rod bearing. I would think though that a wrist pin would get quieter as the engine heated up do to metal expansion but maybe I have it backwards.
Any other thoughts?
Richey

[This message has been edited by STRATOHACKER (edited 04-07-2004).]

ttt

This is an update for anyone who was following this. I finally got time to work on the car. I pulled the oil pan and pulled the #2 rod bearing to check it and to check for play in the wrist pin. The bearing itself looked pretty worn but was not badly gouged and had not spun. I checked the crank journal and it was not scored or nicked. I checked for any play in the rod at the piston and found none. I cleaned the journal, rod and cap and checked the clearances with plastiguage and a new bearing. The oil clearance was in spec. so I installed the new bearing and put the pan back on refilled the engien with oil and changed the filter and fired it up. The noise is gone. I realize that the odds are not in my favor and it may eventualy come back. My hope is that I will be able to get through the summer season and then pull the motor and tear it down in the winter. My fingers are crossed for now and my car is back to it's growling self again with no annoying tick/tock to go with it.
Richey

Sounds like you were pretty meticulous with your repair. As long as both your rod journal, and the big end of the rod are not out of round, you should be good to go.
Just an uneducated opinion.

Good luck, and thanks for posting the update.