Hello, I’m going to copy and paste this question that I asked to reddit.
Knocking sort of noise
I have a Chevy 350 from 1987 and it’s starting to get a knocking noise again. Last time it made a knocking noise it was the cam bolts working themselves loose. I took the engine out again and completely rebuilt it and put it back in. It was fine for about 10-15 miles then it started making a sort of knocking again, with a stethoscope I could hear it pretty well from the timing cover but I also didn’t check the block as thoroughly as I should’ve. I pulled the timing cover and the bolts are still in place and secure. Does anyone know what could be causing the knocking sound? Keep in mind that I’m 16 so there’s a very good chance I’m just really stupid and forgot to do something. The engine had weird studs for some of the mains and I had to use a wrench and hammer to try and get the same amount of torque on them as the rest of the mains. Could the chain gotten loose from when the bolts got loose and let the old cam move back and forth? And then could that be making a knocking noise? I just really don’t want to pull the engine for a 3rd time. Thanks in advance for the help.
Some other things to note are that it does get faster with more revs however it doesn’t seem to get much louder. Any help would be greatly appreciated. I just really really don’t want to have to pull the engine for a 3rd time. Thank you
Do you mean that you disassembler and re-assembled an engine without a torque wrench?
No I used a torque wrench on everything but the studs that I couldn’t figure out, the hold the windage tray or whatever it would be called. I did my best and just counted turns and went by feel. I know that isn’t the correct way to do it
I don’t think I can help you, maybe one of the pro mechanics whp hang out here can.
I do admire your ambition at 16 though.
The farthest bearings from the oil pump are… in front. I’d suggest you have a rod knock.
Did you remove the main and rod caps at the front? Did you see any problems with the bearing shells on those? Did you measure the oil clearance? If not, you should.
It can also be a cracked piston. Higher pitched tapping sound that sounds like a rod bearing is just starting to fail.
In the future, those main cap studs can be tightened with a deep socket or a crows foot wrench that fits your torque wrench.
Thanks, it’s a nice excuse for when I mess things up
I think you’re right about the rod knock. When I took everything apart it looked fine and I I’ll check the clearance. I thought about it and I’m pretty sure it’s going to be number 3 or which ever main has the studs I didn’t properly torque. I’ll make sure to find a deeper socket, thanks
You rebuilt motor? Remaned crank, new rod bearings? Why do u think it’s rod knock?
I didn’t properly torque 3 bolts on the mains, it had these studs that holds the windage tray or whatever that little tray was and I didn’t have a socket that could reach them, so I did the lazy and wrong thing and tried to “torque” them by counting turns and feel. Good idea at the time in my head but now I’m not so sure.
Well, you are not stupid. Ignorant maybe but that only means lack of knowledge. We all are guilty of that to some degree and that includes myself.
Try pushing the crankshaft back and forth lengthwise to see if there is any excessive crank end play that has cropped up for whatever reason. That could lead to noise in the cover or echo noise if torque converter bolts are hitting.
What about the oil slinger on the crankshaft?
In 87 Chevy had carbed, TBI, and fuel injection engines. Which is yours? If carbed, maybe an issue with the mechanical fuel pump push rod, pump itself, or pump eccentric?
I can think of a lot of things to go wrong and the above is only a small slice of them.
Ok I’ll look at the things you said to check. It has a carb but it has an inline electric fuel pump, the block doesn’t even have provisions for a mechanical fuel pump. It also is a manual but I’m guessing that the rear bolt noise applies the same? It’ll probably take me a while to get the pan off but when I do I’ll be sure to check. The great engine placement of the Firebird makes it so the whole engine has to be lifted at least somewhat to get at the pan. Thanks for the ideas.