top end engine knock!!!!please helpppp!!!!

[chobeeboy]

i have a 180 mercruiser and it has a top end knock at the back of the engine, so i replaced the lifters and it still makes the same noise, the people i bought the boat from had it rebuilt in 2006, boat runs fine other than that, and could somone tell me the toque specs for the rocker arms. any help is much appreciated, thank you.

 

[jtybt]

Re: top end engine knock!!!!please helpppp!!!!

Tick, tap, clack, clunk or knock...all technical terms denoting noises made by and engine.

Clacking can be flappers.

 

[chobeeboy]

Re: top end engine knock!!!!please helpppp!!!!

its more like a loud tapping

 

[Bt Doctur]

Re: top end engine knock!!!!please helpppp!!!!

rocker arm bolt torque is 20ft/lbs with both valves closed

 

[jtybt]

Re: top end engine knock!!!!please helpppp!!!!

Loud tapping is not good. Usually means something is very loose. Get a stethescope to locate the noise.

 

[ROBYABLIND]

Re: top end engine knock!!!!please helpppp!!!!

is it a single knock? or more than one? have seen carbon on pistons lead the best tech around in circles.....gm top engine cleaner can help if thats the cause noise more resembles a rod knock - but higher in the engine

 

[Silvertip]

Re: top end engine knock!!!!please helpppp!!!!

With the engine running, pull plug wires one at a time. If pulling the plug makes the noise go away, you have identified the cylinder and it could be anything from piston slap to wrist pin, to a rod bearing. If this engine has an engine mounted mechanical fuel pump check the return spring on the pump lever. Those springs do collapse and without a means of holding the pump lever to the cam you can get a rod knock noise. Replacing the lifters does no good if you have a bent push rod or a rocker arm that was not well lubricated and the push rod socket or the rod end itself has worn to the point where the lifter can't compensate for the loss of material. How about a loose or cracked flywheel. Or a cam bearing. Or a worn distributor shaft bearing. Again, in this case a stethoscope is your main troubleshooting tool. Or you can go hi-tech with a piece of heater hose held to your ear. Works amazingly well.