Welcome.

I would be curious to know what test, or information indicate a cam failure?

 

Hello & thanks for the quick reply. I’m not sure what was done to determine a cam problem. Let me start by say the car sat for several years. It belonged to my father. He parked it when he no longer could drive it. He was 85 years old. I was unaware he even still had it. Unfortunately he passed away & left the car to me. We had a history with a corvette when I was just out of school. He wouldn’t let me buy it. I was 17 at the time. Flash forward some 30+ year a C-4 corvette pulls in my driveway with an elderly man driving. Horn honking. As I walked out the door to my surprise was my father. A friend of his had it. My father had always asked if he would sell it. He stated no I’m saving it for my son who had the time was only three years old. The man became ill and asked my father if he was still interested. he was and he bought it.
So back to the car’s problems. I had to put a fuel pump in it to get it started. Ran really rough no codes, blew out soot & black smoke. Changed the plugs, the wires, distributor and rotor. Both fans were replaced as they did not work.
Temperaturelight came on so I changed Temperature sensors, mass flow air sensor finally got the car so it ran decent. I took it for a ride one day and it started to lose power upon reaching temp? I couldn’t figure it out after a couple months of working on it. I had friends over who tried to help. No luck. So I finally took it to a mechanic who was experienced with Chevrolet’s used to work at a Chevrolet dealership. Built Chevy race car motors etc... He had it about two weeks when he called me and said that it needed the cam. I asked him how he determined it? He said listen to the tick. It had always had the dreaded Chevy tick as I called it. I haven’t got to it yet, but I was gonna pull all the plugs and do compression test on all the cylinders just to see if in fact, I had a bad lobe? But I haven’t got to it yet waiting for the weather to get better. anyway that’s about it. So I know I have a lifter issue. I’m wondering if that’s causing my loss of power? Sorry to ramble on. Thanks Mike

 

You need to start with a compression test, follow that up with a leak down test. Take valve covers off also and check for excessive play on the rocker arms. What do the spark plugs look like?
also you have roller lifters correct? With the exception of bad ones, ive never heard them tick.

 

I'd do a lot more diagnosis before assuming the cam is bad. I removed my '87s stock cam somewhere around 175-180k miles and it looked new. The injectors often sound like a lifter tick in these things. Kind of a clickity clackity sewing machine pattern. Does it bog at a certain RPM? If it has the stock cats one thing to check is if they broke apart after 49 years and are causing a partial exhaust blockage.

Has anyone done any OBD1 logging to look for clues? If it has never been replaced, then I'd be looking at your narrow-band O2 sensors readings in the log for anomalies.

 

thanks for the quick reply’s other than me using my obd1 nobody else has done a check. Injectors was my next thought. Planned on it in the spring when weathers warmer. I have a garage but it has another project going on in it. O2 sensors is something I didn’t consider? Cats were checked by mechanic who said cam was bad and said they were good? So I may have to do that too. Thanks again. Great information from everyone.