Engine knock.

[Plante]

I'm very impressed with the wide range of knowledge contained in our membership.  So what do you think could be causing this???  My '78 440 runs very well, has plenty of power, and except for some normal leaks doesn't use much oil.  It has a little over 80,000 miles on it.  A valve job was done about 5,000 miles ago.  It has an engine knock while just cruising.  If I slow down or step on it the knock goes away.  Opinions vary from worn wrist(sp) pins to a bad harmonic balancer.  It also pings badly when accelerating very slightly. If I step on it hard there is no ping.  It has a new distributor, EGR, intake manifold, and carb.

[Guinnessecco]

You mention both a knock and a ping.  The ping sound like backing off on the timing a degree or two would fix it.  You could also take the distributor to a speed shop and have the advance curve adjusted, both vacuum advance and centrifical advance have to work together.  Having the advance curve adjusted would save money because of better fuel consumption.  Sounds like the new distributor is not quite right for the applicaition.  As for the knock, that takes a really good machanic.  You have valve train noise, rod, main bearing, piston slap, wrist pin, Air conditioning, and I am sure I missed some here.  A good mechanic can actually discern which of these it is just by ear.  If it is a vibration damper, the noise should be located at the crankcase pully. Try this web site http://www.rowand.net/Shop/Tech/DiagnosingEngineNoises.htm

[junebob]

Jerry.
Overall I would have to agree with #316.
As to the crusing nock, I would suspect valve train noise caused by perhaps worn rocker arm bushings.Idealy this should have been corected when the valve job was done.Since it's not a perfect world    Bob Chaney #2626

[Guinnessecco]

One more thought, if the rv has been sitting for a long time, the octane rating of the gasoline will go down.  Gasoline, especially with oxygenates, gets stale in only a few months.  Put some premium in with the stale fuel for you first fillup.  I find 87 works alright with an 180 degree thermostat.  With a 195 degree thermostat I have to use 89.  As you go higher in elevation, the lower the octane needed; however, I find in some parts of northern Arizona, the gasoline must not really be 87 octane at those higher elevations since there can still be a ping.  This is not a problem in other states, that I know of.

[Plante]

I have been using 92 octane gas and have used the rig every month for the past year.  I take it to work with me every few weeks(70 mile round trip) if we don't have a  camping trip planned.  The ping doesn't start until the engine is very warm and it doesn't seem to matter where the timing is set.  I am going to have a good garage check the distributor and vacuum advance.  My regular mechanic doesn't have a sophisticated enough engine analizer.  I'm probably being too picky because my mechanic owned a Clipper many years ago and wishes his 440 ran as good as mine does.

[junebob]

Gerry
    Another thought. Piston slap is usually associated with a light or no load condition. Which would be consistant with idling or cruising.
The power punch in the oil will help oleviate this problem becuase it helps the oil keep a on the cylinder walls.     Some one correct me if I'm wrong, but in my street rodding Flat head Ford days.Wrist pin nock was associared with load such as on acceleration.    
                      Bob Chaney

[HPotter]

Gerry, my brother Bob, a lifelong mechanic, said to tell you that a stuck heat riser that is overheating the carb will cause knock and ping that no amount of tuning will get rid of. So, if you don't have headers, it might be worth a look.

Harold Potter

[Plante]

Harold,
  Don't have a heat riser any more since I installed the Thorley headers.  The rig is in the shop right now(for the past week) and they can't figure out what the knock is.  I received a call at home this weekend from another Clipper owner who said he had a similar knock which turned out to be loose flywheel bolts.  I'm having the shop check that out today.

[Plante]

The engine knock AND ping turned out to be a very sloppy timing chain.  It had 20% slop(whatever that means).  It all makes sense NOW.

[junebob]

Gerry and Donna.
A late perspective on your engine noise that you solved. One of us should have advised you that the fiber timing gear in these old 440s was  atime bomb waiting to go off.Historicallly they fail somewhere between 70,000 and 95,000 miles. Congratulations on your fending off this problem.Bob Chaey #2626  

[Plante]

Thanks Bob - it seems to be running fine now.  Also had to change the fan clutch - we had some overheating during long uphill pulls.