1987 LeSabre Bent push Rods

We just purchased a 1987 LeSabre. It sounded and ran great. the next day it passed an emission test. Right after the emission test, it began to run rough. I changed the plugs, fuel filter, air filter and pcv valve. Shortly after starting the car again, I began to hear a slight tick only to grow to a loud knock and then it stopped. We took the intake manifold off and noticed bent push rods. We replaced the rods and restarted. Same knocking sound. We checked the timing chain, and gears. The harmonic balancer seemed tight. Any idea what caused the rods to bend and what may be causing the knock?

Valves could be sticking in the guides, stuck lifters (which can be caused by poor oil circulation). Or a combination of both.

Which rods are being bent, intake, exhaust, or both?

Thank-you. Both intake and exhaust rods were bent. We visually checked the lifters. When we removed the timing cover,we also looked at the oil pump and packed it with petroleum jelly. We did notice in one of the chambers on the oil filter housing was full of greasy sludge of some sort. We cleaned this out before assembly. Is there an easy check and fix for the possible stuck valves. and lifters?

The rods on my 87 where bent as well when I bought it. I don't remeber what the exact reasoning was, but when I picked up the replacements, the rep said there was some type of issue with the change from a disributer igintion system to a distributerless system that causes this and that it's best to replace the rods each time the cylinder head gaskets are being serviced.

I'm overdue for my gaskets, but still runs pretty decent :dunno:

Funny you would mention the change in ignitions. When we put the plug wires back on, we put them on the way they came off or at least thought. Then we looked in the book and swapped 3 & 6. The interesting thing was the engine didn't run any different and still make the loud knocking sound.

Thank-you. Both intake and exhaust rods were bent. We visually checked the lifters. When we removed the timing cover,we also looked at the oil pump and packed it with petroleum jelly. We did notice in one of the chambers on the oil filter housing was full of greasy sludge of some sort. We cleaned this out before assembly. Is there an easy check and fix for the possible stuck valves. and lifters?
Pull the valve covers, is the upper engine sludged up, if you rotate the engine by hand do all the valves close, possible broken valve springs, look close at the cylinders/valvetrain of the affected cylinders. With the knock you may have spun a bearing and the piston is hitting the valves.