Slant with a bad knock

[SwingerSpecial]

Ive got a 225 with a serious knock, does anyone know how to isolate the problem? I think its either a worn crank or spun rod bearing.

[dschumers]

If it's a rod knock you should be able to isolate it by pulling plug wires one at a time. With the wire off, the knock should go away or at least quiet down. Have you adjusted the valves lately? The lifters can get pretty loud when the rockers are out of adjustment.

[Tim Keith]

I once had a motor knock which was actually a clutch
problem.

I have used a homemade stethoscope made from a piece
of heater hose, you might be able to better isolate the
knock this way.

[SwingerSpecial]

Its had the knock since I purchased the car. Hey, what do you expect for a $150.00 Swinger. Car is an Automatic. Anyway the previous owner said he checked the valvetrain and could not see any problems. However I have skepticism of his mechanical ability. I did the wire pull thing today and the noise did not go away or lower in tone. You cant hear the noise when cranking the engine only while the engine is running. The sound is quiet but noticable at idle and becomes more rapid and raises in octive (extremely) when rpm increases. I would describe the sound as a "rad dat tat tat" very rapid, as if it is overlapping knocks very close together. The engine of course runs very badly stalling frequently. Doesant smoke at idle but when you hit the throttle a thick cloud dispenses. Kinda Like the song:

"Dodge Dart, Dodge Dart..... Shes really smokin! Shes really smokin!"

Im thinkin bad tappet(s) or worn cam lobe(s)?

[dschumers]

Could possibly be a cracked piston or a bad wristpin?

[SwingerSpecial]

Ok so I decide to pull the valve cover off for the first time to see for myself, boy its sure dirty under there. It would appear to be what Ive been told all along, theres a few loose rockers. Can they really get so loud? Im bettin they have never been adjusted for the life of this vehicle. Well maybe once, Id hope. We'll see if this does the trick, this is the first rocker adjustment Ive ever performed. Got my feeler gauges ready. This maybe a decent runnin $150.00 Swinger.

[dschumers]

Good luck!

[SwingerSpecial]

Ok I adjusted the rockers, replaced the plugs cap and rotor, needless to say the engine runs a great deal better. However it still knocks. So it has to be either main or rod bearing or piston slap. Whatever it is the engine will have to be rebuilt. I appreciate your help guys.

[Eric W]

I'm leaning toward piston slap. You said it was faint right? If it was a rod it would be clanging like a bell. The fuel pump could also be making noise. Mine does, and its only 2 months old!
Eric W

[Dartvader]

One of the biggest problems I had with my \6 was having a mechanic adjust the valves thinking it was hydraulic lifters and had them in full contact which made the engine rock like crazy at idle. It didn't sound good either. One of the worst sounds was the leaking intake/exhaust which I mistook for a bad valve problem. Keep looking before rebuilding. I made the mistake of rebuilding and getting no specs.(another story). Just my 2 cents.

[Loghead]

I don't know if anyone else has suggested checking the oil pressure on this engine, (if you have, forgive me) . Any crankshaft related noise will leave you with very little oil pressure, especially after it's warmed up. I also doubt that a spun rod bearing would allow the engine to even turn over-much less run.

[Doctor Dodge]

Checking the oil pressure is a good way to trouble-shoot a bad bottom-end bearing. If a bearing is badly worn or spun, the oil pressure will drop.
In the case of a SL6, the engine will keep running. Bad con rod bearing(s) in a SL6 usually end-up being a hole in the block more often then a seized-up engine.
DD

[Sean C]

When I got my Dart from my mother(273 ci) antifreeze had leaked into the oilpan because of a bad head gasket, after a while the antifreeze had apparently corroded a couple of the rod bearings resulting in a faint knock while decellerating. Although I had good oil pressure the whole time.

So you may have some excessive clearances in your rod bearings.

[SwingerSpecial]

Well Im pretty convinced its somewhere on the mains. When the engine warms up. The oil dummy light comes on. Never seen evidence of any water in the pan.

[moparfienf]

i had a spun bearing that once the motor heated up it would start knocking oil pressure was 40 lbs @2000 rpm so oil pressure doesn't always tell condition. any way pull plug wires one at a time the culprit should quiet with no spark

[Bill55AZ]

Believe it or don't, I bought one once real cheap because of a knock and it turned out to be the FUEL PUMP.

[SwingerSpecial]

Ok Im certain this is an internal failure with either the pistons, rods or crank. Whatever it is will require an engine teardown. So lets look at the worst case scenarios. In the case that it is a spun main what to reccomend? New oversize crank? And what about a spun rod bearing? Will it require that the rod to be replaced or can it be reconditioned? Obviously a case of piston slap would require oversized pistons. Thank You all gentlemen for you contributions.

[moparmnky73]

You might want to make sure that you have the proper oil pressure and if no check the oil pump primer. If not installed paoperly no oil pressure. You can buy a tool that hooks to a drill and helps to manually spin the primer. Remember to time the primer with the distributor afterwords.

:blast: