My 260v8 is knocking is it a rod or is it lifters?

TennesseeDelta · 03-27-2007, 11:23 AM

I just bought a 79 Cutlass Supreme with a 260v8. Car is in good condition two doors good paint and all, when you start it up it starts and idles good. Now here is where I need help, when you give it gas when its in park you start hearing a knocking sound, I though it was a rod ready to go, but when you get out to hear it the knocking is comming from right under the 2bbl carb. And you can only hear the knocking when you give it gas? Talked to a couple of so called mechanics one says its a rod about to go, and the other one says its a bad lifter? Any help please

Oldsmaniac · 03-27-2007, 01:06 PM

A bearing knock is a deeper sound compared to a lifter tap or rocker arm tapping. Noises on a running engine are hard to diagnose at times. A cracked flywheel can sound like an engine about to self destruct. Sometimes you can pinpoint a rod knock by pulling a spark plug wire off each cylinder, one at a time, while running, then rev the engine some. If the bearing isnt too bad when there is no firing going on in the cylinder the noise will go away.

Eightupman · 03-27-2007, 02:01 PM

Simple solution really. Remove whimpy 260, install 350 or bigger!! ALL WILL BE RIGHT IN THE WORLD after that!!

All kidding aside, Oldsmaniac is right on all accounts. I did have a torque converter bolt come loose once (probably not tightend correctly after the tranny change) and I thought the bottem end was about to fall out of the car.

Another way to see if you have spun a rod bearing, is to pull the plugs and do a compression check on all 8 cylinders. Granted its a little more work, but it will give definitive results. The one that has MUCH LESS compression than the rest will be the bad boy.

John

03-27-2007, 11:23 AM	#1 (permalink)
TennesseeDelta Junior Member Join Date: May 2006 Posts: 16	My 260v8 is knocking is it a rod or is it lifters? I just bought a 79 Cutlass Supreme with a 260v8. Car is in good condition two doors good paint and all, when you start it up it starts and idles good. Now here is where I need help, when you give it gas when its in park you start hearing a knocking sound, I though it was a rod ready to go, but when you get out to hear it the knocking is comming from right under the 2bbl carb. And you can only hear the knocking when you give it gas? Talked to a couple of so called mechanics one says its a rod about to go, and the other one says its a bad lifter? Any help please

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

03-27-2007, 01:06 PM	#2 (permalink)
Oldsmaniac Senior Member Join Date: Oct 2005 Location: NJ Posts: 371	A bearing knock is a deeper sound compared to a lifter tap or rocker arm tapping. Noises on a running engine are hard to diagnose at times. A cracked flywheel can sound like an engine about to self destruct. Sometimes you can pinpoint a rod knock by pulling a spark plug wire off each cylinder, one at a time, while running, then rev the engine some. If the bearing isnt too bad when there is no firing going on in the cylinder the noise will go away.

03-27-2007, 02:01 PM	#3 (permalink)
Eightupman Senior Member Join Date: Nov 2006 Location: Fayetteville, NC Posts: 252	Simple solution really. Remove whimpy 260, install 350 or bigger!! ALL WILL BE RIGHT IN THE WORLD after that!! All kidding aside, Oldsmaniac is right on all accounts. I did have a torque converter bolt come loose once (probably not tightend correctly after the tranny change) and I thought the bottem end was about to fall out of the car. Another way to see if you have spun a rod bearing, is to pull the plugs and do a compression check on all 8 cylinders. Granted its a little more work, but it will give definitive results. The one that has MUCH LESS compression than the rest will be the bad boy. John