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help 220 GPU Knocking


I have a couple of intake lifters that have started knocking at idle. The knock goes away at around 1500 rpm. Since there is no adjustment, I'm guessing that I need to replace the lifters. Is that correct or is there something else I should do? Also can these be replaced without removing the cylinders?

Why do you think they call them Clunkinentals?

You might be hearing the counterweight on the crankshaft clacking.

My 220 Continental clacked below 1000 rmp the whole time I had it but it ran great.
The way to set the preload on the lifters is by changing the pushrod length. If you need to preload the lifter more you need a longer pushrod. You can get pushrods that are longer or shorter then standard from aircraft suppliers, but it is easier to use some chromolly tube and make your own. I am probably going to be running adjustable pushrods on my 520 when its done, custom jobs that look like harley pushrods.

double check to make sure your prop adapter nuts are tight. ive seen quite a few people who thought they had a "knock". sold theyre boats only to find out is was the prop adapter.
Thanks everyone. I'm pretty sure it is the lifters. I used a mechanics stethescope on the covers and tubes. The #1 cylinder intake and the #4 cylinder intake seem to the the source of the knock. The rest sound fine.
Anyway thanks again!
I see a lot of lifters bleed down and cause excessive valve clearance problems. That excessive clearance is probably causing your knocking noise. If your valve clearance was set good that should not have changed. A longer push rod is not going to make a bad lifter get quiet. The noise goes away at higher RPM's because you are making enough oil pressure to keep the lifter "pumped up". You can check/change the lifters without removing the cylinder. You have to pull the rocker box cover and remove the rocker arms. (You have to bring that cylinder to top center to relieve the spring tension) Then pull the push rod tubes. (There is also a special tool I have for removing the push rod tube springs). After that you can remove the three 1/4" nuts and remove the plate to reveal the lifters. The lifters have a small clip that holds them in the cam followers. That clip is a trick to remove and another trick to get it back in. Then you should be able to pull the lifters out with a small wire with a hook on it. It is a fairly easy job, but you will need some special tools.