Hello fellow mopar lovers I have a ?
so I have a 1972 plymouth scamp fresh 360 mild build. Broke in the cam and it ran great but i never drove yet because i was still trying to tidy up other little task on the car....so i finaly took it for a spin around the block and half way through the drive I hear a thud sound. Now the car stayed running so I babyed it home. There is a knocking sound that no one can seem to figure out what it is. My engine builder says it's not the motor and the noise only occurs when I give it a little bit of throttle. Some say it could be the flex plate or the torque converter. So if anyone knows any info would be greatly appreciated thanks!

 

Without hearing it, it's almost impossible to guess. The sudden thud doesn't sound good. Almost like something let go. Take the cover off the lower bell housing and inspect the flex plate. The converter only goes on one way so that's out.

 

So I did check out the flex plate and it's brand new. Someone said it could be something broke inside of the torque converter. Could that be possible? Wish I could post a video.

 

72 -

Yeah, tough without hearing it in context.

When EXACTLY does it happen? (When starting to roll, on acceleration, in park/neutral and adding gas, only on a roll?)

Archer

 

It happens in park when i give it gas at idle its quiet and sounds normal

 

The chances of the converter being bad or even making that noise is just about zero.

 

Could it be the trans pump? Any ideas of what you think it can be. Is there anyway to send videos on here? I know it's hard to figure it out if you can't hear it.

 

Is the Noise coming from the front of the engine? or The rear ?

 

The sound seems to be coming from the rear

 

Check the bolt heads of the torque convertor and see if they are touching the engine block.... You can also look for a little forward thrust on the front crankshaft pulley...
And just a question on that note.... You did use the correct flexplate to convertor bolts? OEM Style?

 

I had the pleasure of talking with this owner. He certainly put a bit into his engine by having a machine shop rebuild it. Where the fly entered the ointment is when the builder advised him to use a "BREAK-IN OIL" He recommended a low ranked break-in oil 5w30. This oil is slightly better than running water through your engine. The wear capabilities are rated at 47,483 psi which ranked second to the last at #297 on 540RAT's oil test chart. A flat tappet engine should have at least 100,000 PSI protection. He also recommended revving the engine for 20 minutes to break-in the camshaft and lifters. Under article #63 Rat explains the do's and don'ts on break-in. Good reading that could've saved this engine.
Blog engineer 540RAT said with almost absolute certainty his engine was damaged by bad advice.
The logic I apply to engine break-ins is new cars from the factory back in the day of muscle, didn't do all the revs and break-in oils at the factory and they ran fine. When we assembled a motor, we would spin it over until the oil light went out and start it with the choke off high cam until the oil pressure built up and drove it. We had no issues.

 

72 -

Just for giggles, motor and trans mounts bolts still in there?

Archer

 

So you have talked to Mr. 72? And his engine is blown up? is that what you mean?
or am I missing something?

 

It sounds like a serious internal knock. Completely blown, probably not. I'm thinking the camshaft/lifters took a beating during break-in. The Main and rod bearings of course are suspended hydraulically for the most part so probably did ok. A tear down will tell the story.

 

I'd take the rocker covers off and look. If the cam is trashed you can probably see from there. Did you drain the oil? Was it shiny?

 

Yeh maybe wiggle around the rockers and pushrods and see if something is loose or just listen to the upper end while running. I don't believe you'll be able see the camshaft without yanking the intake off.

 

Oh.. OK.... The engine developed a Valve Train issue.. Still pending teardown. Got it...