1971 360 Engine Knock

[kp6401]

Hi All, I bought the 71 Sport Fury from Fearless Fury. I have replaced the inner and outer lower drivers side quarter panel so far (work too much to do anything else). Replaced the trans fluid and filter and eliminated the leaks.

Fearless identified a motor knock that I am trying to resolve. He did awesome work replacing everything on the top end. As I have been cruising, you get to the point of about 45 to 60mph and there is an egregious knock that occurs. I have spun main bearings on cars, those knocks are really loud, this is bizarre. It sounds like on the top end, but I just am not sure. I replaced the oil with SAE straight 30 and put in STP motor honey hoping it would quiet down, it hasn't. Further, when I get the car to normal operating temp, at low idle I am getting the idiot low oil pressure light. I am beginning to think I have weak compression rings and it may be starving for oil. I have had several 360's that had a light floating knock at 60-80mph, but this is really loud. I am suspecting it is time to overhaul the mains (rebuild). The car has just shy of 76k on it, but was in hibernation many years until Fearless rescued it. I am going to cruise it and try and record the noise to post here. Any help would help, otherwise as I do the passenger side lower quarter this winter out will come the 360 for a rebuild, as well as the trans as the parking pall is croaked. Thanks, and I will get some pix posted up here of my driver side lower quarter repair. I really like the car, just work 2 jobs and struggle to find the time.

 

[Davea Lux]

You probably need to stop driving it now and determine the cause of the knock, before you wind up picking pieces of your expectant motor off of the highway. It is about to make babies all over the road. A couple of things you can try. If you have a knock at idle try disconnecting one plug lead at a time, if it stops knocking, you know that that cylinder has a bad rod bearing. A bad main bearing will usually knock on start up and again after the oil thins due to the warmup of the engine.

Low oil pressure after warm up is usually an indication of bad main bearings. A floating knock is most likely a rod that is failing to to the lack of proper oiling, either because the main bearings have failed or the pickup screen for the oil pimp is clogged because of debris from a failing timing chain. Either way it is time to park it and pull the oil pan to see what is going on.

You can plasti-gauge both the mains and rods to check clearance but most like you are headed for a rebuild.

Dave

 

[65sporty]

I remember the posts about his engine noise, as Dave has said above it sounds like time for a rebuild. Pull the pan to be sure.

 

[kp6401]

Thanks, I really appreciate the input. You hit the nail on the head - I move it in and out of the garage only - no more road trips - don't want to scatter it all over.....

 

[celticwarlock]

I agree completely that you likely have main bearing issues, and that the resulting reduction in oil pressure may well be causing other problems elsewhere.

I have seen other motors with similar ailments be repaired successfully by correcting the clearance issues with an in-vehicle bearing replacement & Plastigauge check, but as I'm sure you know, it's best to remove the engine entirely. There's no sense getting that involved only to discover that something's out of spec and that you have to remove it anyway.

 

[moper]

Might be a wrist pin noise. My truck's had one for about 10 years now. Gets very loud at times and I've had people say it's a rod. But the oil pressure doesn't go down or change and it's not a rod... If your oil pressure changes (drops) then it's not a wrist pin.

 

[johnny ga]

the oil light coming on is a sign of worn out bearing with too much clearance.