Engine tapping

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

 

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.

 

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.

 

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

 

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.

 

Tapping Noise

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

 

Noise Frequency and Location

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.