Engine tapping

[James Francis]

I have slight engine tapping/clicking noise in my 305 4 barrel engine. Recently tuned, with new plugs and wires, points/cap rotor, rebuilt carb. Boat still has lots of power but an annoying tapping/ticking. One more thing I found interesting - the port exhaust water is hot while starboard exhaust is warm. Could this be a sticking exhaust valve? Has anyone had any luck with chemical additives like valvemedic to free the valve?

Thanks,

James

[Frosty]

You have faulty hydraulic valve lifter. No big deal it wont fail.


If you want to replace,-- its normal to change all 16,--or use solids and an adjustable rocker kit. Some would argue you should change the cam too!!

I personally feel your temp difference is normal --there are a few threads running on this complaint.

[smokeonthewater]

You didn’t mention if it was only happening under load or all the time, if it’s only under load it could be "pinking" (pre ignition) this could be due to a bit too much advance on the timing.
If it’s a lifter, unless the engine is relatively low hours I would change the cam as well because if your lifters are worn so will the cam be and a worn cam will wear the new lifters faster.

[Frosty]

Hydralic lifters sometimes fail on the hydraulic side, its not necessarily an age related problem.

[PAR]

It also could be a bent push rod, a loose retainer nut on a rocker, plus a few other things. You can hope the super oil thingie will cut it, but an inspection by a mechanic would be a better, likely more informative method of finding the problem.

[James Francis]

Thanks to all of you for your analysis. The tapping happens at idle and under load - but again, the performance and power are normal. I will monitor the noise and have a mechanic take a look during lay-up.

Cheers,

James

[TerryKing]

The assumption seems to be that this is a valve-train related noise. But you might try to verify that:

• Get a short piece of hose, hold to one ear, move it around both valve covers etc. Where is the noise located?
• Is the noise at camshaft speed (1/2 crankshaft speed)?? You should be able to judge this at idle, knowing what valve noises usually sound like.