I'm at wits end! I have a 1964 425 dual quad that my dad gave me. He rebuilt the engine and then parked the car after approx 20 minutes of run time. When he rebuilt it he bored it out .30 and installed new pistons and dual quad cam with new cam bearings. It then sat for about 15 years.it was stuck when I got it. I pulled the heads off and found some stuck valves. I rebuilt the heads and replaced one guide. I had todo some cleaning in the cylinders and they looked pretty good. I fired it up and at first had a lot of blow by but eventually smoothed out and sounded good. Before wrapping it up for storage I decided to pull the oil pan. I found about 2" of jello in the bottom of the pan (old oil). I cleaned it up and wrapped the engine up in shrink wrap for approx 2 years. Eventually the frame was done, driveline installed and body put back on. I started the engine again. It sounded good...... for awhile. I started getting a knock. At first it sounded like a lifter and then got stronger. It was always on the passenger side. So far (in order) I've replaced the fuel pump, pistons, rod bearings, lifters, pushrods, oil pump, cam, rockers and now I have it apart again! my total running time since I got it has been approx 2 hours. It doesn't go away when warm.its louder under low load. Oil pressure is good, compression is good, power feels good. i hear the knock the most when I put a piece of hose to my ear and have the other end at the second cylinder from the front on the passenger side where the block meets the head. that cylinder measures at 4.345 and the piston measures at 4.318. one last note: when I replaced the cam, one of the new lifters that I put in previously was spalled in that same cylinder. this probably my fifth time taking this apart for this problem. whats left? What am I missing?
Anything said on here is a guess, guessing is expensive, my advice is take it to a professional engine builder and let them go through it, otherwise strip it down and start again on the measuring path to find out whats not right
If the measurements you gave for #3 cylinder are correct that's your problem, .027" is about .025" to .026" too loose. If the cylinder actually measures 4.345 (meaning it was bored .032" from original of 4.3125") the piston should measure 4.342" at the least for a clearance of .003". If the .027" REALLY means .0027" then it's a little loose for a cast piston, but OK.
I've had a few come through the shop that had .010-.015" clearance with cast pistons. Clearance @ .010" it MAY cold slap for a few seconds and go away, due to the offset of the wrist pins and the fact that a tapered or distorted bore has an actual running clearance less (tighter) than the total deviation. .010" isn't really .010" unless assembled fresh. Clearance @ .015" it bangs immediately to the point you wouldn't continue to run it. I've seen one worn .030" and not make much noise, but that piston had strong offset and the robust skirts had already been 'conformed' to the bore. Unfortunately, I haven't seen enough of that condition actually running to accurately predict your knocking condition, just that I'm going to question the measurement or place on the piston that was measured. I have seen many scores of engines with actual clearances like that... NOT running and there's an absolute TON of damage along with that Some inspection and teardown is in order!
You've probably already done it, but did you have a look at the timing gear sprockets and chain? One that's slightly loose can make a heck of a racket, as can a slipping harmonic balancer. I've heard of water pumps making noise too.
Larry, Does your car have factory AC? Does it have a fuel return line which originates at the fuel filter? If so, the noise you are hearing may be hydraulic hammering in the return line. This has been well documented and vetted in the first gen Rivieras. If you need any more info PM me, Tom
