3.0 tap/knock

[Mskeels]

Hello everyone. I rebuilt my 3.0 Merc and have some sort of tap/knock around piston no3. Any advise and direction in solving. I have no interest in taking it to a shop as it’s a hobby and like to learn!

I couldn’t notice anything moving in the bottom end.

TIA

View attachment IMG_0370.MOV

 

[dubs283]

First "distributorless" 3.0L I've ever seen, not many out there

Sounds slow enough to be a valve/lifter issue

Would recommend a mechanic's stethoscope, cylinder drop test, running without the belt, removing the drive and running the engine, try running on the water under a load, etc....

 

[Alumarine]

If you suspect 3 have you tried backing off and then tightening the lifters for 3 to see if the sound changes?
Did you plasti-gauge the rod bearings?

 

[Mskeels]

First "distributorless" 3.0L I've ever seen, not many out there

Sounds slow enough to be a valve/lifter issue

Would recommend a mechanic's stethoscope, cylinder drop test, running without the belt, removing the drive and running the engine, try running on the water under a load, etc....

Thanks bud. Removed the coupler so no drive and used a stethoscope seams like it’s around the no3 cam area. Really cant see anything

 

[Mskeels]

If you suspect 3 have you tried backing off and then tightening the lifters for 3 to see if the sound changes?
Did you plasti-gauge the rod bearings?

Yep tried the backing off the lifters. Didn’t use plastic gauge on bearings as new and crank was done

 

[Scott06]

Yep tried the backing off the lifters. Didn’t use plastic gauge on bearings as new and crank was done

I would be checking the clearances and also wrist pin. doesnt sound like valvetrain to me but could be. Even if it was machined check them always. I have had to take rods back that were resized wrong.

was it bored? I had an old volvo that on real cold starts would have some piston slap until it warmed up which sounded similar. This was due to forged piston cold wall clearance being more than typical cast piston.

 

[04fxdwgi25]

sure sounds like a loose lifter / rocker arm.

 

[Mskeels]

I would be checking the clearances and also wrist pin. doesnt sound like valvetrain to me but could be. Even if it was machined check them always. I have had to take rods back that were resized wrong.

was it bored? I had an old volvo that on real cold starts would have some piston slap until it warmed up which sounded similar. This was due to forged piston cold wall clearance being more than typical cast piston.

I would be checking the clearances and also wrist pin. doesnt sound like valvetrain to me but could be. Even if it was machined check them always. I have had to take rods back that were resized wrong.

was it bored? I had an old volvo that on real cold starts would have some piston slap until it warmed up which sounded similar. This was due to forged piston cold wall clearance being more than typical cast piston.

Thanks I’ll look into this. Do the conrod widths look large?

 

[dave8311]

Sounds like a rod knock to me.

You didn't check bearing clearances?

 

[Scott06]

Thanks I’ll look into this. Do the conrod widths look large?

View attachment 396528

I would check the side clearance on the con rods vs spec. In your first post the main bearing cap is off was there scoring on the crank?
you said crank was done by whom ?

 

[Mskeels]

I would check the side clearance on the con rods vs spec. In your first post the main bearing cap is off was there scoring on the crank?
you said crank was done by whom ?

shop did the crank. well know local guy. no scoring on crank bud

 

[Mskeels]

Its the side clearance on con rods that look big?

 

[Scott06]

Its the side clearance on con rods that look big?

Can tell from the keyboard. It’s making noise so you need to go through and measure all the clearances vs spec. If you don’t have the mI do eters would take it to some one who does

 

[dave8311]

shop did the crank. well know local guy. no scoring on crank bud

That pic before or after you ran it? Wrong bearing clearance will mess up a newly machined journal.

Are those rods not the ones that came out of that block, originally?