Engine knock

77RS · 05-27-2009, 08:42:36 PM

I've got an '85 Camaro that I bought a few weeks ago just to fool around with. it has been sitting for 10 years. I finally got it started, but it's got a knock in the engine at idle. The knock goes away above 1k RPMs. At first, it knocked at all RPMs, but seems to be smoothing out. Any ideas whats' going on here? Would a rod knock smooth out like this?

74Lt1 · 05-27-2009, 09:12:12 PM

a rod knock would get louder as the rpms went up... atleast mine did... Probably need to give it a refresh if its been setting that long.. I would put new mains/rods and cam bearings in it to start... look everything over real good... replace anything that looks like it needs replacing. Thats the easiest thing to do other than trying to chase down a knock. because sometimes you cant chase it down. you have to tear it apart to find out for sure what it is.... JMO hope this helps..

77RS · 05-27-2009, 09:40:02 PM

That's what I was thinking. It should get worse at higher RPMs if it was a rod. I know it needs to be gone through, so that's what I'll probably do. What other probs would cause a knocking sound? I just wondered it it was even worth the trouble to do. I bought this car for a fun summer project. Don't want to put a ton of money into it. I'm saving that for my 2nd gens

Thanks

1972L · 05-27-2009, 09:48:04 PM

Piston slap
or a stuck/sticky wrist pin

77RS · 05-27-2009, 11:02:47 PM

What exactly is piston slap? I've heard of it, but not sure what it is. I'm enocuraged to know that there are other possibilities besides a rod knock

ProStreet383 · 05-27-2009, 11:03:55 PM

Quote:

Originally Posted by 1972L

or a stuck/sticky wrist pin

This is my guess. I bet after it runs a while it goes away.

ProStreet383 · 05-27-2009, 11:05:50 PM

Quote:

Originally Posted by 77RS

What exactly is piston slap? I've heard of it, but not sure what it is. I'm enocuraged to know that there are other possibilities besides a rod knock

That is when the piston rocks in the cylinder bore and "slaps" the bore. Heck now days a lot of new engines have piston slap from the factory. Once the engine warms up it goes away. My 99 SS camaro has piston slap on cold mornings.

77RS · 05-27-2009, 11:40:03 PM

Great! I've got some carb issues now that are causing probs in starting it. I let it run for about 15 mins one day though and the knock seemed to ease up. It still knocked when below 1k RPMs, but not as much as it did when I first started it. So you guys think that after I get all the juices flowing good again this may not be a major prob after all?

When I got the car, the oil smelled like gas. I replaced the fuel pump and oil. Cold oil pressure was at 60 PSI; warm it was around 32-34 PSI at idle. Seemed good to me?

74Lt1 · 05-28-2009, 08:19:07 PM

The specs for oil pressure i think is 40psi at 2000rpms. Thats what my chilton book says... so your psi should be ok.. what kind of knock is it? is it like a peck? or a solid knock? there are lots of things that can knock... let it set and run some and see if it stops.. It could be a lifter or anything... could have bearing problems... if its a cam bearing i think they smooth out with rpms... Thats what the local machine shop guy at NAPA told me... Cam bearings are only about 15 bucks... Probably about $30 to have your local machine shop to put them in... Main bearings will usually rattle when you first start it if they have wear on them... try to tell us alittle more about the knock your experiencing..

77RS · 06-16-2009, 10:49:34 PM

Thanks for all the info guys. I decided to do a little upgrading before pulling the engine. Changed the oil and added some mojo to loosen things up.

Also... new dist cap, rotor, coil, wires, plugs, carb, fuel pump, hoses, filters, etc. that engine is running great now. It kept up the noise for a little while but finally cleared up. I think that I also had a sticky valve that cut loose today. the engine idles and revs perfectly. i'm happy with it. Thanks again!
Daniel