390 knock - Ford Forums - Mustang Forum, Ford Trucks, Ford Focus and Ford Cars

theshowson · 07-28-2011, 13:53

Bought a 68 Mercury parklane w 390/4v as a project with my son...supposedly it was rebuilt in 1979 w/87,000...it now has 123,000 but who knows...it needed some work but was driveable...when the radiator started leaking, I decided to replace it and everything else in the system...waterpump,hoses,thermostat...then may as well do the timing chain/cover/fuel pump...so all that done...it started right up but had a descernable knock on the front lower end it didn't have before the work....I listened everywhere...but couldn't located it...so I took everything back apart...it's not the fuel pump or water pump and i see nothing wromg with the chain or gears but can still hear it...any ideas? My thought was rodor main bearing or piston pin but the noise wasn't there before this work...

FFR428 · 07-29-2011, 11:27

I'd double check the fuel pump arm is the correct one for a FE. Sometimes rebuilts get the wrong arm/box or parts guys assume they are the same. When they are indeed a bit different. A fuel pump with a small block arm will make a tapping noise when installed. May not be the case here but worth a look to compare it's correct.

theshowson · 08-01-2011, 08:45

I triple checked the fuel pump...it's correct...I put my kid's stethescope down near the oil pump with the timing cover off...it's definately lower end...equally as loud on either side of the crank ge...with no other ideas, I drained some oil, added Lucas and put it all back together...it is much improved but I can still hear it...most pronounced the first 2 seconds after start up then quiets dramatically...so is that a rod or main bearing going?
Thanks for the input.

kdtrucker · 08-01-2011, 12:22

If your hearing it on start up then it goes away I would tend to think it's the main bearings. What is your oil pressure reading??

If it is the bearings,...when you replace them, make the oil slot in the bearing as big as the hole in the block; ( use a dremmel) that will help in delivering more oil to the bearing.

theshowson · 08-02-2011, 03:00

The car has an oil pressure idiot light. I wanted to know what the oil pressure was so I bought an otc mechanical to help diagnose this issue...I was able to get 35psi spinning just the starter motor...