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Old 08-28-2009, 02:02 AM
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Engine knock diagnosis advice...

Hey Gang...

Wouldn't you kow it...I FINALLY get my Rod project done, and now the engine is knocking! Arg!

Anyways, I am at a bit of a loss in diagnosing the source of the know. Here's the info...maybe some of you guys could give me an idea...

The engine is a solid lifter, .30 over 1965 Plymoouth 273ci with an a833 4 speed.

It has an aftermarket rear-sump oil pan and pickup tube.

The sound is a loud knocking which is heard loudest throught the stethoscope at the back of the oil pan (nearest to the tans). Sounds like the crank is hitting something. I drained the oil and dropped the pan thinking that the crank was hitting the oil pickup tube..not so. There is NO sign of the crank touching anything.

Checked the oil pump (ie. took it out and spun it manually), checked that the pickup tube was tight, checked the thrush bearing...no wear...

No metal chunks in the pan

Checked the play in the crank...less than 16th of inch lateral play.

Checked the sparkplug wires

Flywheel is on tight, no leak in exhaust manifolds.

Not a valve issue, as engine runs perfectly when it's knocking.

Running 35-40lbs of oil pressure, so I don't think it's main bearings.

The odd bit is...when you engage the clutch (ie. the flywheel is being pushed forward) the noise almost completely disappears! Returns when clutch is released.

The next step is to check all the rod bearings.

I REEEEAAAALLLLLYYY don't want to have to disassemble the front end again to remove the motor! I am hoping that maybe one of you guys will know exactly what it is, and that I can fix it while it's in the car.

Any info would be great. If one of you guys have a definative idea, I can snap a movie of the troublesome knock.

Thanks!!!!

Ty

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Old 08-28-2009, 05:43 AM
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Are you sure it`s coming from the engine? Have you removed the rod caps 1 at a time and checked the bearings? The throw out bearing maybe bad or possibly the pilot bushing is worn causing the tranny input shaft to have enough play to knock. When the clutch is disengauged there`s no load so the input shaft is free to move around if the pilot bushing is worn, when you engauge the clutch the pressure plate holds it in position so the shaft can`t move. Not sure if this will help any, but it does give you more places to check. Before I did the rebuild on a 4.3 chevy V6 it knocked when the clutch was disengauged. Upon tear down I found the throw out (release bearing to some) was worn completely out and the pilot bushing wasn`t in much better shape. After replacing the clutch with a ram unit and installing a new rollerized pilot bushing no more knock.

Last edited by DoubleVision; 08-28-2009 at 12:44 PM.
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Old 08-28-2009, 09:39 AM
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Sounds like a throw-out-bearing to me.
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Old 08-28-2009, 12:32 PM
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Quote:
Originally Posted by Tyroma
Hey Gang...

Wouldn't you kow it...I FINALLY get my Rod project done, and now the engine is knocking! Arg!

Anyways, I am at a bit of a loss in diagnosing the source of the know. Here's the info...maybe some of you guys could give me an idea...

The engine is a solid lifter, .30 over 1965 Plymoouth 273ci with an a833 4 speed.

It has an aftermarket rear-sump oil pan and pickup tube.

The sound is a loud knocking which is heard loudest throught the stethoscope at the back of the oil pan (nearest to the tans). Sounds like the crank is hitting something. I drained the oil and dropped the pan thinking that the crank was hitting the oil pickup tube..not so. There is NO sign of the crank touching anything.

Checked the oil pump (ie. took it out and spun it manually), checked that the pickup tube was tight, checked the thrush bearing...no wear...

No metal chunks in the pan

Checked the play in the crank...less than 16th of inch lateral play.

Checked the sparkplug wires

Flywheel is on tight, no leak in exhaust manifolds.

Not a valve issue, as engine runs perfectly when it's knocking.

Running 35-40lbs of oil pressure, so I don't think it's main bearings.

The odd bit is...when you engage the clutch (ie. the flywheel is being pushed forward) the noise almost completely disappears! Returns when clutch is released.

The next step is to check all the rod bearings.

I REEEEAAAALLLLLYYY don't want to have to disassemble the front end again to remove the motor! I am hoping that maybe one of you guys will know exactly what it is, and that I can fix it while it's in the car.

Any info would be great. If one of you guys have a definative idea, I can snap a movie of the troublesome knock.

Thanks!!!!

Ty
I concur with the previous findings of a bad throwout bearing and will also suggest that the pilot bearing in the end of the crankshaft may also be out to lunch.

This does not sound like a crank assembly bearing issue.

Bogie
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Old 09-04-2009, 07:00 PM
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Hey gang..

Well, I decided to take the transmission off and try that to see if the problem was in the pilot bearing, or throwout bearing...nope...still knockin.

So I dropped the oil pan and checked the rearmost rod bearing...

Alas, it would appear that the rod bearings are not well...so after having completed my build in mid-August, I now have the unpleasant task of disassembling the front end..again..and remove the engine, tear it down and fix it.

I am not pleased, but I guess I was looking for a winter project...

Thanks to all who replied.

TY
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Old 09-05-2009, 12:36 AM
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this time get the connecting rods big end resized.
See your local automotive machinist. He will help you.
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