Strange knocking from #8 area..
 

Gen 6 502 has developed a loud sharp metallic clack from the #8 area. I am not able to isolate it with a stethoscope. It almost sounded like a bolt on the coupler had backed out and was striking something in the bell housing at the 10 o'clock position. Removed engine and nothing loose on coupler or flex-plate.

The noise is not directly timed to engine RPM. If you hold rpm steady at fast idle the sound is consistent. Blipping the throttle would increase the rate but it sounded like at certain points during rpm increase or decrease it would go away momentarily or change its pitch.

Stethoscope place on directly on rocker studs revealed no culprit. Pressing on the rockers did nothing to quiet it down. Oil pressure is 60 at warm idle. Compression check showed 160 lbs on all holes. Plugs look fine.

The sound was more of a sharp metal to metal contact sound that is why the mechanic and I suspected a bolt had backed out, it was not a dull thud like a rod. Since we found no bolts or coupler trouble we are suspecting it may be a valve seat rocking around it the head but are puzzled as to why we could not hear it localized on a rocker stud.

Other possibility is wrist pin or piston skirt?

If a valve seat is getting ready to drop would I be able to spot this visually when I get the head off and valve out? What am I looking for in this area?

Here is the kicker. Heads were just done by reputable machine shop. New lifters and rockers. Ran fine for 8 hours then the noise developed. I suppose it is possible that a wrist pin or skirt is bad but usually when something goes wrong it is the last thing you messed with as in the heads.

Engine is out of the boat bolted to a jet ski trailer. I can drop the pan to look at the bottom of 8 or 6 but not sure if I could spot a cracked skirt. I want to isolate what the problem is before sending the short block to the machine shop. If possible I would like to avoid tearing the engine apart if I can confirm a problem with the head.

Any tips for physically finding the cause of noise? What can be spotted by visual inspection?

Re: Strange knocking from #8 area..
 

I know this is too simple but this sure sounds a lot like a flapper in the exhaust banging. What exhaust system do you have?

Re: Strange knocking from #8 area..
 

I was thinking the same thing.

Re: Strange knocking from #8 area..
 

I had Corsa on my checkmate and the first time that I heard it the hair stood up on the back of my neck! It didnt take me long to isolate the problem though. I hope that this is the noise you are hearing and that it is'nt a problem at all.

Roger

Re: Strange knocking from #8 area..
 

Folks, I am aware of how a flapper can sound. This noise is coming from inside the engine. I have a Merc Master Tech looking at with me. This is the guy Merc sends customers to when many other dealers cannot fix things.

Anyway got the head off this morning. Cylinder walls are fine. Not a scratch in them. Unable to get the triple valve springs off because the tool has morphed legs and scooted under a bench somewhere. Tie bars on lifters are fine. Lifters ae pumped up solid. Unless it is a valve seat (will know more when the valve comes out), I am looking at wrist pin or piston skirt. Might be time to send off for full rebuild and throw the old stock 454 back in for a month or so.

Re: Strange knocking from #8 area..
 

Well, we didnt know what you knew and didnt know. Sometimes those flappers can be un-nerving. Hope its nothing serious but please keep us informed what you find. I know wrist pin noises pretty well and this doesnt seem to fit. The top of the pistons looked ok huh? Damn. If you set a dial indicator on the deck and measure the piston movement of say #6 against #8 with the same degrees of crank rotation each way you might be able to pick up a problem on 8 if there is one. My quess is still in the head.

Re: Strange knocking from #8 area..
 

Well the heads were the last thing touched so I am taking them back to the machine shop for inspection. I did spray carb cleaner into the intake and exhaust ports and nothing came out the combustion chamber. Still possibly a seat? My worst case scenario is to take it all apart and not find an obvious cause. I plan on pulling the pistons early next week. Sort of busy right now. I really hope I find a bad skirt or pin. Then I have to decide to either replace the piston and go on with it or do the full rebuild. Probably close to time, 550 hours but walls, oil pressure and compression is fine. May as well do it while down but is very late to start that type of work.

I need luck...
Of the correct kind...

Re: Strange knocking from #8 area..
 

Valve sticking maybe, check guides and stems real good. Another thought, windage tray or intake valley splash tray. Ive heard of a windage tray coming loose and hittng making strange noises that were inconsistant. The thing about it not being timed to the motor is wierd. Did you use a timing light on #8 to see if the knock was related to the top end firing and valve events of #8? I know, too late now.

Re: Strange knocking from #8 area..
 

Have you actually pulled the lifters from the bores? I have seen something like this with a failed roller.

Re: Strange knocking from #8 area..
 

That's what happened to me. Could NOT locate the noise last fall. Tried everything, then finally a lifter came apart and not only did the noise stop...well you can use your imagination on what happened next!

Good luck

Dave

Re: Strange knocking from #8 area..
 

Hmmm, I suppose that may could be the trouble. After I rule everything else out I will throw the old lifters in and re-assemble with cheapy gaskets. If noise is gone that was it.

Re: Strange knocking from #8 area..
 

Bad,
That sounds like it could easily be a rod bearing too. Have you cut the filter open to see if there is any bearing material in it ? Rod bearings usually will not affect oil pressure when they first start to fail. Wrist pins or a loose skirt will usually not start all of a sudden, even though it can happen.
Did your machine shop install seats in the heads ? I have done 4 pair of 502 heads this spring and none of them needed seats, they were about the hardest material I have ever seen. Could be a valve sticking when hot, but you probably should have been able to pick that up with the scope on the valve cover.

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

Re: Strange knocking from #8 area..
 

What ever it is PLEASE let us know.

Re: Strange knocking from #8 area..
 

That knocking is money trying to get out of your wallet. :(

Re: Strange knocking from #8 area..
 

My bet is a valve guide has gone bad, if that is the case, be sure to replace that valve also, because they get to rocking around and are prone to break off a piece of the valve or the whole mushroom, and that gets real ugly.

Re: Strange knocking from #8 area..
 

Head is at the machine shop now. Never heard a noise that could not be determined after a few beers. Those that heard it were split between rod, lifter, skirt, broke ring and where is the beer. I will find it...

The cooler that is.

Re: Strange knocking from #8 area..
 

BadDog...any updates on this problem?

Re: Strange knocking from #8 area..
 

Sounds like you are about to spin a rod bearing.

Re: Strange knocking from #8 area..
 

:stupid:

Re: Strange knocking from #8 area..
 

Yup, caught it just in time. The rod bearing was spun but still there. Part of the bearing was hanging out and hitting as the crank turned. Getting new Eagle I beam rods and turning crank. Upgrading to forged pistons while it is down. Sucks that this had to happen in the spring. Should have took it out over the winter but everything seemed fine last fall. Good oil pressure and no noise.

Re: Strange knocking from #8 area..
 

Better spring than summer :D

Unfortantly I have been in your shoes. I was even to the point I was going to build a spare engine. I have every thing I need execpt a block to put all the parts in :(

From the school of hard nocks, remember to clean everything. You might not see the metal particals but they get every where. I thought my oil cooler looked clean after spinning a bearing. Well 10 hours later I blew another engine. Can never stress enough about cleaning everything.

Good luck.

Re: Strange knocking from #8 area..
 

Builder is removing cam bearings and flushing block to clean it out. I will run a fire hose through all cooler lines and cooler. I planned to flush with water/soap mixture and follow up with diesel fuel then oil. Any better plan of attack to flush cooler and line?

I had a spare 454 ready to run. It was stored at the Fire Department and it disappeared. Bummer..

Re: Strange knocking from #8 area..
 

I thought I had the oil cooler clean also. New engine lasted 10 hours :mad: A little short cut cost me thousands.

By advise of my machine shop, get new oil lines also. I went and had them custom made while I waited for $40.

I have heard of several people running oil cooler before filter even on brand new coolers, just incase some thing was in the cooler.

Don't forget lifters will contain particles also :eek:

Re: Strange knocking from #8 area..
 

I feel your pain. :mad: Did that done that last year around the same time. :( Unfortunately for me, something else when wrong last week :( . So instead of pissing my summer off like last year, I ordered a new 502 long block :D . Hopefully I will only be down a week and not like 3 months like last year :rolleyes: . Like Jim said, "better spring then summer".

PS.....Just replace the oil cooler. not worth taking chances. I learned the hard way. I did not change my cooler after a spun bearing. New motor lasted less the 10 hrs.

Re: Strange knocking from #8 area..
 

I think I will start a new thread on best oil cooler for the buck. I have not inspected my cooler yet but I cannot see why it would not be possible to fully clean the oil cooler. Is there something in the construction that prohibits fully flushing it?

Re: Strange knocking from #8 area..
 

Tim, did you get a chance to run the boat after the blower rebuild? Any performance improvements?

Re: Strange knocking from #8 area..
 

Do a search you will find them on cleaning oil coolers.
#1 I don't think you could do it for a reasonable price for what they cost to replace.
After my learning experience I cut my open to see what it looked like. It was not loaded with metal but you could see it stuck in between the tubes. When you have thousands spent it is no place to cut corners.