knocking, cold and under load
- Thread starter mwood
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MOC
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you could try the seafoam 3 way ( 1/3 in fuel tank ,1/3 in in the block ,1/3 threw the mastercylinder brake vacume line .
Sea Foam Usage Video
YouTube - How-To Seafoam
works .
These are easy ways to spread it 3 ways to help the motor ,can only help clean it out ..tho when you put in your block ,you got to change the oil in a 100 miles or so cause it is cleaning the inside of your block .When you suck a third through the booster line you have to have someone throttle the car so it won't stall ,,shut it down and restart 15 mins latter ,the other 3rd . is going in your gas tank . Stuff really wakes your car up ..Cleans it .
Sea Foam Usage Video
YouTube - How-To Seafoam
works .
These are easy ways to spread it 3 ways to help the motor ,can only help clean it out ..tho when you put in your block ,you got to change the oil in a 100 miles or so cause it is cleaning the inside of your block .When you suck a third through the booster line you have to have someone throttle the car so it won't stall ,,shut it down and restart 15 mins latter ,the other 3rd . is going in your gas tank . Stuff really wakes your car up ..Cleans it .
not good. Sorry to scare you, but it sounds like rod knock - maybe spun or worn bearings (main or rod). How's the fuel pressure? If it's erratic, it's a sure deal, but if not you aren't off the hook.
Chris
Chris
I concur with the rod knock assesment. Good thing they can be rebuilt dirt cheap. Wish I could say the same for my mod motor. 
I'm in the process of building a 408, so a rod knock isn't horrible. I just need to understand the likelyhood of the car leaving me on the side of the road.
I'm thinking about the rotating assembly and trying to imagine what the rod could be knocking against to make a loud thud. Someone describe this to me. The rod isn't broke free. It can't be. It shouldn't even run at that point.
I'm thinking about the rotating assembly and trying to imagine what the rod could be knocking against to make a loud thud. Someone describe this to me. The rod isn't broke free. It can't be. It shouldn't even run at that point.
Over 100k miles have been running 89 w ethinol, just filled up w 91 w ethinol. Really shouldn't be detenation unless being out of timing could still do it.
It tics when I rev to higher rpms. Been told that might be a spun bearing, but a hard knock?
the sound would be the rod hitting the crank every time it moves toward where the potentially spun or worn bearing is supposed to be. Rods typically "float" on a film of oil. Without enough oil-pressure in that spot the rod is making metallic contact with the bearing and/or crank. The rod hasn't broken or the engine wouldn't run.
There's no way to know how long you can run the engine in that condition before it ****s on itself. If you're going to junk it, then no big deal, but if you'll rebuild with that block you should stop driving right away. If you'll continue to drive it, keep the RPM low and stay light on the throttle, ensure that you have 'ok' oil pressure and it might/probably will last a couple thousand miles in that condition. However, it might just chew up the bearing/rod/crank and send metal all throughout the rotating assembly which will likely cause the motor to fail and seize up the next time you drive it. If you put the engine under hard loads it won't last long for sure.
Oh, and in my last post, I didn't mean to reference fuel pressure, oil pressure is what I meant.
Chris
There's no way to know how long you can run the engine in that condition before it ****s on itself. If you're going to junk it, then no big deal, but if you'll rebuild with that block you should stop driving right away. If you'll continue to drive it, keep the RPM low and stay light on the throttle, ensure that you have 'ok' oil pressure and it might/probably will last a couple thousand miles in that condition. However, it might just chew up the bearing/rod/crank and send metal all throughout the rotating assembly which will likely cause the motor to fail and seize up the next time you drive it. If you put the engine under hard loads it won't last long for sure.
Oh, and in my last post, I didn't mean to reference fuel pressure, oil pressure is what I meant.
Chris
Oh, and to add a little more, the reason that I think it knocks cold and not hot is because as the engine warms up, thermal expansion causes the tolerances to tighten which brings up oil pressure and that helps to buffer the rod in question.
If it's just a ticking sound, it could just be your valve train (pushrod, lifter, a rocker that needs adjusting or replacement)... but you said it was like a mallet hitting the block, and that would indicate something more serious.
If it's just a ticking sound, it could just be your valve train (pushrod, lifter, a rocker that needs adjusting or replacement)... but you said it was like a mallet hitting the block, and that would indicate something more serious.
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