Hey guys, I recently picked up an '82 z28 crossfire injected 305. To my knowledge everything is oem except I changed to ngk plugs, and an msd cap&rotor with 8.5mm wires. It is running better, but there is some sort of knocking. I generally don't enjoy going to the mechanic when usually a little research can go a long way, but I can't figure this out. Plus I live in Ca. so I need to get the car to pass smog before I get in trouble for expired reg. while it's parked. Any ideas would be greatly appreciated and if you need some more info on the car, or other details let me know. Also, at the end of the video you see me hold some sort of cable that comes up from the passenger front wheel well. I have no idea what it goes to, or if it is important. The previous owner was a deuch who had the speedometer cable unplugged and a few other things less than desirable. Also the oil pressure gauge isn't working, I believe the sending unit is in the rear of the vehicle, but i'm not sure if that could be an issue as well. Thanks again dudes!

here is the youtube post where I loaded the video, not sure if I could load here or not.

Thanks again guys, I need to get this resolved or gone asap.

 

cant see the video oil pressure gague mat be working ,and you may not be getting oil , knock knock isn't good.

 

the oil pressure guage is not working, I have the repair manual, but all it says is test the sending unit in the rear compartment. Is there any way to verify the oil pump is working, without that guage, or can you run me through troubleshooting the guage? Thanks for the reply.

Tomorrow, I will pull the belt off, and try to see if it's something belt driven, but other than that I'm at a loss.

For what it's worth, the plug wires were in the wrong order when I got the car, so i'm not sure if that could have damaged something?

"video is now public" sorry

 

The easiest way would be to hook up a mechanical oil pressure gauge and see where the oil pressure is. From listening to the video its sounds like a tap rather than a knocking. It also sounds like its much louder on the driver side. Could be coming from a lifter or rocker.

 

Spun rod bearing

 

Thats what I am afraid of. Any rough idea what I would be looking at to do a rebuild? At that point am I better dropping in a 350? Im not trying to spend a fortune on this, the guy said it just needs a tune up. Im a sucker. Will it last a few months while I save for/start building another engine? Will a mechanic be able to tell for sure, or is it gunna be guess and check?

 

On mine car the oil pressure dropped and the noise cam after, the noise would come and go but would get louder as the days went on

Get a 350 and rebuild it out of the car then drop it in

 

sounded a lot like a loose rocker arm to me-could remove the LH rocker cover and check for a loose rocker or other problem.If it is a rod bearing,could rebuild the 305 or build/get a 350-you will need 350(corvette 82-84)injectors and ECM chip along with a computer friendly cam to run the CFI on the 350.To increase performance of the CFI,certain manifold and fuel pump modifications should be done

 

A couple of people say it sounds like lifters, and reccomend putting some auto trans fluid in and then changing oil. Guess ill give that a whirl. As far as rocker arm, would it be something obvious by looking at them with the valve cover off? The oil pressure guage is "pegged" should I just replace the sending unit when I change the oil? Im assuming its fairly simple ans straight forward , located by the filter. Thanks for the advice thus far, at least I can check a few things before dropping major cash.

 

On a side note, can I theoretically build an engine in a second story apt.? I figure weight is about 600-800lbs so a few buddies can get it downstairs? I know, I know, I know, my other option is to just rent a small garage for $125 a month. All my tools are in the apt fyi.

Just trying to figure options at this point.

 

building an engine in an upstairs apartment can and has been doneIf you have to do that,you could just build the shortblock in the apartment and add the heads and other parts once shortblock is installed in the car-installing the heads with block in car is easy and fast and a couple average guys could carry the shortblock down.

 

rocker arm noise to me.

 

Sounds like a rod knock.

 

Update, when I put it in drive the rpms drop to about 700 and it wants to stall. Occasionally it will backfi. Out of the exhaust then blow white smoke ( doesnt smell like coolant) for about 10 minutes. The water temp goes up then drops back down. No oil in coolant or pressure in overflow, no residue on dipstick so I think the head gasket is alright. Maybe timing or vaccume leak?

 

Is the knock coming from high on the engine are low? You can use a broom handle, sick one end to the engine and the other to your ear. Put it on the valve cover,then move it too the engine block. If the knock is low in the block it probable is a rod,
if its high it may be valvetrain.

 

Your kidding, right? From the sound I am hearing in the video I am almost positive it is a rod knock, either that or your flexplate has a crack in it. If it's knock, then there is a reason for it. If you want help I will give it to you. Grab a pair of pliers with a rubber grip, and with the engine idling, remove one spark plug wire at a time from the distributor listening to see when the knocking stops. When it does stop, you found your bad cylinder. Pull the spark plug from that cylinder with the engine off and take a good look at it, this will let you know if you detonated. But either way, from the sound of it, the engine needs to be pulled, and the bearing needs to be replaced. If you wait too long, piston slap will inevitably get worse and worse, and soon your cylinder walls will get scored up. Take care of it now before it gets worse...

 

Check out the Renegade manifold swap if you build it. I have a sick liking for crossfire setups. It's pretty rare, and pretty awesome when someone mods them into a good strong runner. An intake swap and TB rebuild and balancing really wakes them up.

They're actually pretty simple to work on and pretty reliable.

Oh, and the that sounds completely like valvetrain.

 

Agree, sounds like (a) loose rocker(s).
Could be,
rocker nut backing off
rocker stud pulling out of head
cam lobe/lifter wearing down

 

A collapsed lifter would cause the engine to cough upon acceleration in gear, and a loose rocker arm sounds more like an exhaust leak does, not as heavy, and more like snapping one's fingers, not mention loose rocker arm noises go away as RPM is increased. Careful inspection of the video shows the noise loud and prevalent, and getting louder when he blips the throttle at 44 seconds into the video. His oil pressure gauge is also not working, so he needs to use a mechanical gauge to see if pressure drops as RPM is increased, as well as pull each spark plug terminal from the distributor to source where the knock is coming from. That is definitely a spun rod from what I can hear...

 

Still Sounds like a rocker arm to me.

 

Hopefully the maker of the video will be honest, and will follow through with another video showing what he finds out. I for one HOPE its a loose rocker arm, as I don't want to see him have to pull the engine out, but sadly he more than likely has to because it sounds like a spun rod bearing to me. In any event, I wish him or her the best of luck with it...

 

After listening with a stethoscope it sounds like its coming from behind the exhaust manifold towards cylinder 1. Ill pull the plug tonight if I can ( living in an apartment with no parking spaces sucks). When I changed the plugs the old ones were still gapped propperly, black, wet, and reaked of gas. Ill also pull the rocker cover and check that out. Is there anything other than obviosly loose nuts to check for? I appreciate the help, I have the fsm and can usually figure crap out, but not haveing space to work is really inhibitive. On another note I hooked a vaccume guage to the manifold and it was reading 18in/hg, but the needle was pretty shakey with no huge fluctuations. (Loose valve stem guides).

Ill try to dig in more asap and will let you guys know what turns up.

Thanks again

 

Look at your rocker studs, they should all be close to the same height.
Same for the nuts, close to the same.
Depending on where your motor is in its cycle you may have some rockers tight(open valve)
Try to get motor TDC on compression stroke so both are closed.
They will be a bit loose in the closed postion but shouldnt be crazy loose

 

Stupid question, is there anywhere topside that I can accurately check oil pressure? My property manager gives me grief anytime I lift the car up. Otherwise its midnight auto mechanic for me.

Ive read that many small blocks have a small plug above the timing cover and below the intake manifold on the front of the block for this purpose, but am not sure what I am looking for.

 

Take off your air cleaner, to the right of the distributor you will see a canister with a 3 wire connector plugged into it that's the oil pressure sending unit. unscrew it and thread an oil pressure gauge in to the fitting.

 

Just saw this thread - I had that same sound years ago and it wound up being a wiped cam lobe causing the issue. Take off the valve covers and make sure you have full movement on all the rockers.
If it is not that it could be a bad lifter or loose rocker. But it is definitely valvetrain noise.