I have a 240 six in my 68 F100. While waiting at a signal all of a sudden a tapping noise started coming from my engine. It's noticeable at idle gets loudest at around 1300rpm and seems to go away at higher speeds or is just not noticeable with all the other noise. I thought it might be a bad lifter so I pulled them and found one that had collapsed and had a bent pushrod, so I replaced the pushrod and all new lifters and readjusted the rockers but the noise is still there. It kind of sounds like a pushrod is bouncing off a lifter, but I ran it with the rocker cover off and every thing seems to be OK. The noise seems to be coming from lower than the valvetrain area. There is no noticeable lack of power or compression. I also checked the fuel pump and its OK. Also pulled the pushrod that had bent before to see if it bent again but it was OK. Hope you guys can help. Thanks

 

Could be a rod knock, a piston skirt knock or a bearing going bad :-X23 My neighbor ran one with a knock for years but it was just a farm truck too.

You could drop the pan and do a cheap (I don't like this method myself) re-bearing of the crank bearings.

It's your choice weather to do it "right" or do it cheap. Depends on your wallet, how many miles are on the engine and how long you want it to last.

Bob

 

Something bent that push rod find that and you will find your noise. Usually caused by piston hitting valve. Either lifter stuck or something is on top of the piston.

 

Oh yea something had to bend it they just dont bed on ther own Ford I6 have a common problem also with breaking and or cracking piston skirts. I have a I6 that has about 45k on a piston skirt that has broke it runs fine and I am not going to rebuild it untill it dies

 

I used a mechanics stethescope to locate the noise and it seems to be coming from the camshaft at the first lobe on the #1 cylinder. You can barely hear it at idle then gets loud up to about 1300rpms then turns into a ringing noise at higher rpms. Sounds like I may have to pull the camshaft. Any other suggestions? I checked the valve movement and it seems OK and I don't feel any strikes hitting any of the valves pushrods or rockerarms.

 

Make sure the oils flowing to everywhere it needs to be. If parts are running dry, they'll start talking to you.

 

My guess would be a worn cam bearing. They usually sound bad at idle, then "smooth out" as rpm increases, and sound like ringing or jingling a pocketful of change. If you pul the cam, be sure to check or replace the cam bearings. A lot of guys overlook that.