Engine Knock

[anunknownpresence]

My '84 Regal has a '71 Rocket 350 in it and started to make a horrible knock last Sunday. I was traveling 70 mph on I-75 when it started.

I've checked all possible sources of where the knock could be coming from as it is hard to pin-point the noise. I checked the flywheel for cracks, damage, and loose bolts and that checked out fine. I removed the valve covers to check the valvetrain and everything seems to be working fine, although normally the valvetrain should make a bit more of a mess with the covers off and only the valves and lifters at the second cylinder squirted any oil. I know it couldn't be a loose timing chain because the engine runs great aside from the knock; there isn't a bad miss and it always starts right up.

My oil pressure normally ran about 20 psi but now fluctuates wildly between 20 psi and 40 psi, sometimes as much as 50, although that's rare.

Anyone have any ideas? I'm a little stumped on this.

Thanks.

 

[patmckinneyracing]

My sbc 350 in my malibu started having the same problem. It developed a knock after it overheated one time. The problem that we came to was a collapsed lifter. My oil pressure used to be 20-40 psi on the street but now barely gets 22 psi on the highway now. A lot of times its 1 out of the 16 lifters in the valley.

 

[turbo78]

sounds kinda like you got a main bearing spinning in the journal of the block and your oil pressure is fluctuating because of it, the knock is probably the rod jumping up and down on the loose rod journal next to the bad main journal... more than likely numbere 1,or2 cylinders... good luck, sorry to hear you are having issues.

 

[Minion1186]

i think its the lifters,anyone know how the old oldsmobile 350 diesels sound at idle?with that strange cranking sound like metal with no lubrication,well thats how my engine sounds now.It's not exactly loud and you'll have to listen closely to hear it but i think because of my lead foot and too many bad cold starts i've killed a lifter.So its a possiblitly its a lifter,olds engines stock dont like to be revved over 5 grand,if you do they'll blow up without drilled holes in the block to accomodate my lube going to the valvetrain.

 

[anunknownpresence]

Well my worst fears were confirmed. :shock:

Looks like I might be in for a rebuild whenever I get the money.

Thanks for the opinions everyone.

 

[turbo78]

so what was it?

 

[anunknownpresence]

so what was it?

Given what I know and what you told me, I'd almost bet money you're right about what's going on with the engine. It especially makes sense because I have had a few people say that "it sounds like something worked loose in the engine."

This sucks because the Regal was my Daily Driver. I'm going to keep it, but I chances are I'm going to try to get another car.