360 engine knock even after crank and bearing replacement

[MPcarter]

My neighbor pulled a running low mileage (but sitting for years) 360 out of a 1977 Dodge truck and put it into his 69 Barracuda which had a 318 in it originally. Within about 5 minutes of starting it up in the car the engine started knocking like a box of hammers shaking around. He pulled it back out, saw that the rod bearings were bad and replaced the rod bearings and oil pump and put it back in. It was quiet at first but within 10 minutes it started knocking again. He pulled it again, replaced the crank and all bearings (came as a kit) then sold the engine to me cheap because he didn’t want to deal with it. After reading some Mopar forums online I learned that it was probably caused by the 318 flywheel that he used which threw off the engine balance. I purchased and installed the B+M 10236 flex plate and the Jegs 51671 harmonic balancer then I installed it in my 1975 Coronet which had a 318. I used the original 318 torque converter because from what I saw online and from what Summit racing tech support told me it was the same as the 360.

The engine was quiet as a church mouse at first, but within about 20 minutes of the car running and taking a couple short trips around the block its knocking again. Should I have changed the torque converter as well? Or could this be another issue all together?

 

[Auggie56]

May have a loose fitting piston or wrist pin ? At the distributor cap, take the rubber boots on the wires, and pull them back so you can unplug the wires easily while the engine runs. Warm the engine to the point where it knocks. Using insulated pliers, remove one wire at a time till a change in the noise is noticed. That will be where the problem is. What your libel to find, is a bad piston, oversized cylinder or a lose wrist pin.

 

[MPcarter]

Thanks Auggie56, I unplugged the wires one at a time. #1 stops the knock completely. When I plug it back in it knocks hard. So my problem is with #1. I'll have to pull the motor and tear it down to see exactly whats going on with #1.

 

[WP29440SE]

the 318 is internally balanced and the 360 is externally balanced so you must use the matching balancer and converter, or at the very least add or remove the weights for your application. Summit also sells a flexplate to compensate for the weights.The 318 converter does not have weights but the 360 converter does. The 360 balancer is much bigger than the 318

 

[Lelo 500]

A neutral balance converter on a 360 would cause a major imbalance.

 

[dvw]

The wrong converter/flexplate /balancer will cause a vibration but not noise. Does it run smooth? If so look elsewhere.
Doug

 

[RT K_line]

What is the oil pressure? An imbalance won't usually take out rod bearings. Something else is going on. Is it always the same cylinder?

 

[MPcarter]

Thanks for all of the replies. I have the correct 360 balancer and flex plate. I don't have a vibration, just the knock, and only on #1. It runs fine other than that.
I'm going to pull the engine soon and see whats going on.