Engine is Knocking

[jackman]

My engine has a knocking (tapping) sound. You can hear it in the engine compartment but to me it is more pronoucned under the truck. Could it be my exhaust collectors? It does increase with engine speed. Ive put a scope on the intake and valve covers but it doesnt seem to be coming from there. Ive also takin the belt off ran the engine but the noise is still there! Please Help!!

[wileys_farm]

what year and vehicle type you got. What size engine.

[jackman]

1990 Chevy 454ss truck with a 454 markIV engine with TBI A/T

[wileys_farm]

first like you said check your exhast. You should clearly hear an exhast leak they are very distinctable. If its pecking and NOT a heavy knock its probably just a lifter or valve. What I would do first is run a quality motor flush through it in the next oil change. This will loosen the lifter, if that is what it is. Put a little heavier weight oil in it. Like if your running 10w30 go with 10w40 this should quietin the engine. If nothing works and you should pull the valve covers and readjust the valves. If its a rod knocking dont spend anymore money on the engine,"unless your overhauling it", No type of oil additives will replace lost metal no matter how much they advertise. Dont waste your money on "scam" products. Good luck



wiley

[jackman]

I did check the valves again it still seems ok. I did notice that when I pushed the end of the rocker arm down kinda hard the engine wanted to stall and even shut off is this maybe a bad lifter? I will change the oil and put thicker oil in it tommorrow. If I pull the oil pan off will I be able to check the connecting rods to see if they are real loose? What about the oil pump no pressure maybe although my oil pressure guage says it is around 35 psi?
Any more help is welcome!! Thanks.

[wileys_farm]

If your pulling the oil pan to check the rods you can check the bearing by pulling the rod caps off. It will be hard to check just by trying to move the rod. If you do feel slack by just moving the rod that is your problem. You shouldn't feel any slack in the bearing, because there is only a couple thousands of in play in the rod for the oil to coat the bearing. You can install new rod bearings without taking the whole engine apart. It must be done very carefully not to jerk all the rods off at once. The rods that are hanging the lowest do them first. Crank the engine"by hand" until one more comes down and so on. The reason you dont do all of them at the same time is because you have no way to push a piston down for the rod to connect to the crank. Take your time and you can put "rod" bearings in that thing without pulling the engine. Usually if you have bearing failure you need to find out why the bearing failed:

high milege
high rmps's
bad oil pump
debre in oil
oil not changed

If your rod bearing are bad you can just about garentee that it needs main bearing too.

[jackman]

I found out what the noise was it is my timing chain to much slack I guess hitting the cover. I put thicker oil in but it didnt change. So I went back with the scope over the whole engine and when I put it on the timing chain cover it was loud!!!!!. Dont know how I missed it the first time? Thanks for all the Help. If I can help with anything let me know or post Im always looking at them. Thanks again!