Knock in motor - Team Camaro Tech
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post #1 of 21 (permalink) Old Sep 27th, 05, 07:29 PM Thread Starter
 
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Knock in motor

I ahave a knock on the passenger side . I have checked all of the valves and reset timing. I have heard if it is a rod knocking, you can isolate it by pulling the plug wires one by one. If the sound goes away, a rod is the culprit...

Any truth to this and how does this work????
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post #2 of 21 (permalink) Old Sep 27th, 05, 08:44 PM
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Jim
 
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Re: Knock in motor

rod knocks are loud, and very metalic. Like someone is banging a hammer on an iron bench vise. If you "pop" the gas, it gets really loud when everything "unloads" just before the rpms start to fall back down. Once you've heard one, you never forget. I still got the piston with half a pretzel attached to remind me of one I hoped would go away.... in a 69 vette, years ago...things been sitting on a cabinet in my shop for 20 years...





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post #3 of 21 (permalink) Old Sep 27th, 05, 09:11 PM
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Eric
 
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Re: Knock in motor

Actually if you pull the spark plug wire the knock should get worse! One more thing... Remember a rod knock will often sound like banging your knuckles on the oil pan.
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post #4 of 21 (permalink) Old Sep 28th, 05, 04:42 AM Thread Starter
 
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Re: Knock in motor

This knock is driving me nuts! I used a stetosope and can hear it through the valve cover, I can hear it through the intake manifold and anywhere else in contact witht the motor. I have had a bad rod in another car in the past and it sounded nothing like this-It was very loud! When RPM s increase i cannot hear it over the engine noise...

I have pulled the Fuel pump, reset the rockers, reset timing,checked for exhaust leaks....

Any suggestions where else to look?
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post #5 of 21 (permalink) Old Sep 28th, 05, 06:59 AM
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Jim
 
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Re: Knock in motor

I'd guess you don't have a rod knock. Like I said, if you've heard one before, you'd know that sound in an instant.

Is the bottom of your oil pan dented? It could be that the oil pickup is pushed into contact with the crank?

A "for sure" but messy way to make sure it's not the valvetrain is to loosen each rocker while it's running, listen to see if it's the "same knock" getting louder, or a new one. (don't do this with a solid cam!)





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post #6 of 21 (permalink) Old Sep 28th, 05, 05:16 PM Thread Starter
 
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Re: Knock in motor

I have tried this with the valves. Loosened them until they clacked and then tightended 1/2 turn- No change in sound...

Anything else???
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post #7 of 21 (permalink) Old Sep 28th, 05, 07:12 PM
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Smile Re: Knock in motor

Is the engine old , rebuilt? Have you noticed any drop in oil press? When did the knock start?
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post #8 of 21 (permalink) Old Sep 28th, 05, 07:32 PM
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Re: Knock in motor

Piston Slap? Bad Piston pin? If its that bad,, you could pull engine in a few hours and if motor is old,,, well its out. Couldn't be a rocker are hitting the valve cover baffle?

Don
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post #9 of 21 (permalink) Old Sep 28th, 05, 08:24 PM Thread Starter
 
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Unhappy Re: Knock in motor

The knock can be heard when the valve cover is off...The engine is a 63 327 . From what I was told it was rebuilt about 2 yrs ago. I never noticed the knock until the exhaust was changed to a quieter setup. I have seen no drop in oil pressure, but do now have an oil leak on the backside of the motor that I cant see... The oil drips down off the bellhousing cover..
When i loosened the rockers, I am assuming this would have made it worse had it been a bent pushrod... I am thinking next would be to pull the intake manifold and see if anything looks out of whack....

Thoughts?
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post #10 of 21 (permalink) Old Sep 28th, 05, 09:13 PM
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Re: Knock in motor

Water pump bearings can knock too. Power steering pumps also. I have even heard strange noises off of fan belts that have gotten coolant on them. Did you ever try pulling the spark plug wires? What happened? You can have a quiet rod knock also. It just means that there isn't tons of slop in the rod bearing. The last rod I lost would only knock under load or when you revved the motor slightly as the RPM's were coming back down. Once it got to idle it was quiet. Remember... Check the small stuff first. How bad will you feel if you rebuild the motor and it turns out to be the water pump!
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post #11 of 21 (permalink) Old Sep 29th, 05, 05:45 PM Thread Starter
 
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Unhappy Re: Knock in motor

Ok folks , heres where I am at... I tried pulling the plugs while the car was running. Most caused the car to reduce in idle-Others had no effect (None produced a change in the knock) I figured it was a little weird so I pulled the dist cap and cleaned the rotor and cap well . I checked resistance and all wires are good and I am getting a spark through each.Still, The car is not idling well , it is missing and no change to knock. I did however notice that my fuel pressure gauge is jumping back and forth from 6-8 lbs. in perfect rythme with the knock. This leads me to believe the problem is in the valve train. ( I had already pulled the fuel pump previously)

Already tried:
Fuel pump. Adjusting rockers,timing,

What do I look for from here???

I really appreciate all the help to my dumb questions!
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post #12 of 21 (permalink) Old Sep 29th, 05, 06:00 PM
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Re: Knock in motor

When you removed the fuel pump did you take a good look at the spring and lever? You might try removing the pump again and pour a little gas down the carb and start it with the pump off to see if the noise goes away
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post #13 of 21 (permalink) Old Sep 29th, 05, 06:56 PM Thread Starter
 
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Re: Knock in motor

I just removed the pump and let it run on the gas in the line. No change..

There was one other thing that may play into this... When I was setting the rockers, the nut on #2 exhaust rocker was very easy to turn, the rocker tightened up but the pressure required to turn the nut did not go up as it tightened.. I dont know if this could mean anything-Just thought I would mention it.
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post #14 of 21 (permalink) Old Sep 29th, 05, 07:18 PM
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Re: Knock in motor

I had a 396 that sounded just like this , it ended up having a broken piston skirt and a major amount of piston to wall clearance . We bored it out .030 over freshened it up and it sounds just perfect now .
Mark .
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post #15 of 21 (permalink) Old Sep 29th, 05, 08:06 PM Thread Starter
 
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Re: Knock in motor

I am hoping that is not the case...

Im looking to eliminate the smaller issues first... Any suggestions?
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