Mercruiser 2.5 ticking sound

[dirkg]

Hi! Working on an old project boat with a mercruiser 2.5 engine (first generation block with a cilinder head, studs and hydraulic valves from a second generation block). I've been bashing my head recently on a tick that's being produced by the engine and I just can't seem to resolve it.

The tick seems to be coming from the left side of the engine, close to the camshaft and lifters. I've already adjusted the valves (multiple times), cleaned all hydraulic lifters and checked if the tick is also there without the fuel pump installed. It's linked to the RPM, as you can hear in the video below and definitely sounds to becoming from the push rods area.

Nothing seems to be working and I'm pretty much at the point of lifting the engine and opening up the oil pan to see if there's anything suspicious with the cam and such

Before doing so, is there anyone here that recognizes this sound and can point me to something? Or convince me that this is supposed to be there (which I can't imagine most as I've not heard it before) Thanks!

The video with the sound of the tick at different rpms:

 

[alldodge]

Doesn't sound like rods, more lifter/valve noise

Look at the rocker arm nuts, do they all look to be in about the same place?

Might have a collapsed lifter or 2

Could remove the valve cover and take a long screw driver. With motor running put metal tip or screw driver on rocker stud, and place the handle snug to your ear. Listen to all and see if one or 2 of them are louder

 

[dirkg]

Doesn't sound like rods, more lifter/valve noise

Look at the rocker arm nuts, do they all look to be in about the same place?

Might have a collapsed lifter or 2

Could remove the valve cover and take a long screw driver. With motor running put metal tip or screw driver on rocker stud, and place the handle snug to your ear. Listen to all and see if one or 2 of them are louder

So I've cleaned all hydraulic lifters before (pulling then apart, cleaning, refilling, etc), tested again, and even replaced them for another set I had laying around. Didn't do anything, tick still there.

Nuts are pretty much in the same place as well from what it seems.

Have been testing with a hose to see if I can pinpoint the sound. Seemed to be coming mostly from either cilinder 2 valves or 4. Then again, not really sure what to do with them as it feels like I've touched and cleaned all parts between lifter and arm so far.

Could we possibly be looking at a worn cam lobe or sth, especially given this head on the other block (which I replaced because it cracked) didn't make the tick?

 

[alldodge]

Could we possibly be looking at a worn cam lobe or sth, especially given this head on the other block (which I replaced because it cracked) didn't make the tick?

Opinion
If it was a worn cam lope then the noise from that cylinder would be more then others

Have you run the motor without the drive on?

Have you done a warm compression test?

 

[dirkg]

Opinion
If it was a worn cam lope then the noise from that cylinder would be more then others

Have you run the motor without the drive on?

Have you done a warm compression test?

It's hard to pinpoint the noise to exactly one place, but I do feel it's coming more from the second cilinder...

Haven't ran it without drive, nor done a warm compression. What's your thinking? Got another day of fiddling tomorrow (CEST time here) so can definitely do some more tests and likely pull the engine out.

 

[alldodge]

If the noise is coming from a burnt valve than it will show up in a compression test

If compression is within 10% all cylinders than remove drive to make sure it's not coming from it

 

[dirkg]

Thanks. I'll do some more tests tomorrow. It's just still puzzling me that this head was working fine on the other block (if it's valves), but tests will tell...

 

[kenny nunez]

A fuel pump with a broken return spring will make a noise like that, Try removing the pump and check the spring.
Another source could be a worn valve guide.

 

[dirkg]

Not the fuel pump, replaced that one for another one I had laying around and no difference.

Pulled out the engine today and will run some proper tests on it this week as suggested. Compression, timing, valves etc etc. Hopefully I'll find it

 

[svb165]

Be sure they gave you a head gasket for a 2.5 and not a 3.0 it will leak and tick,,, granted,, not like what you are hearing, but just a thought. btdt

 

[Scott Danforth]

So I've cleaned all hydraulic lifters before (pulling then apart, cleaning, refilling, etc), tested again, and even replaced them for another set I had laying around. Didn't do anything, tick still there.

could be collapsed cam lobe. since flat-tappet lifters mate to that lobe for life, swapping lifters will just speed up the process.

could be timing gear is missing a tooth or two. these motors had a phenolic timing gear that lasts about 15-20 years. being a 2.5 liter, the motor is at least 35 years old.

a compression test will point out any hanging valves

coupler splines could be worn

core plug behind the block in front of the flywheel could be working its way out and ticking the flywheel.

 

[dirkg]

Alright, so the engine is out and I've run some tests.

Compression (4-3-2-1)
Cold: 135,129,129,140
Warm: 135, 143, 145, 145

Removed the oil pan, visual inspection didn't show anything, no play in the cilinder bearings.

Coupler is obv ruled out at this point since it's out of the boat.

Timing was a it behind, adjusted it back to 8°BTDC @ 700RPM per manual. No difference

Tried to nail down the origin of the sound again by listening to it with a tube. Definitely sounds to be coming from the distributor/fuel pump/cilinder 1/2 area.

I've got no tools to pull the crank pulley so can't look at the gears atm, but feels like that would be my next step(?).

I've got another camshaft from the "donor" engine if which I also pulled the head. Feels like I'm getting to a point where I'm going to pull the pullet, check the gears and perhaps just swap the camshaft for the other one (which would also unite it again with the lifters).

 

[Scott Danforth]

check the dizzy for worn bearings. its $13 worth of bushings from NAPA

 

[svb165]

check the dizzy for worn bearings. its $13 worth of bushings from NAPA

DIZZY ??

 

[cyclops222]

They can not take the time to spell distributor.

 

[svb165]

They can not take the time to spell distributor.

I had ta ask

 

[dirkg]

check the dizzy for worn bearings. its $13 worth of bushings from NAPA

Anything particular to look for? Took the distributor off and compared the bearings with the other engine I've got laying around. No visual differences, nor can I feel any play in it or what so ever.

In the process off swapping cams atm, got the donor one out, just need to start ripping the engine apart and replacing it (and much hope for it to be the solution )

 

[Scott Danforth]

There should be no axial or radial movement of the distributor shaft within the housing

 

[cyclops222]

Is it safe enough to mix-up all those cams , lifters, and pushrods ?

 

[dirkg]

Is it safe enough to mix-up all those cams , lifters, and pushrods ?

Bringing the cam over to the "new" engine actually unites everything back up again, as I previously moved over the lifters, rods and head (and kept each "vertical" united with each other).