TravisF

Recently I have noticed a popping sound coming from under the hood under hard acceleration. Under normal driving conditions, I don't hear it at all. New plugs, New wires, timing is on the mark, TPS is where it should be. Anyone have any ideas? Possibly the distributor?

TravisF

Sorry, forgot to mention, stock 82 base model. Thanks,

Patro46

Does the popping noise sound like a backfire?

TravisF

No, doesn't seem like a backfire, I've seen it backfire through the drivers side TB once a while back, and this is different. This happens continuously only during hard acceleration....pop, pop, pop, pop, pop...... as soon as I let back on the throttle, it stops. I can recreate the sound running, in park, from under the hood by manually moving the throttle linkage.

1Fordman

Is the popping back coming from the intake manifold? That's one of the signs of a flat cam. It shows up under hard acceleration.

TravisF

It does sound like it is coming from the intake manifold.

1Fordman

Take off the valve covers, bar the engine over and watch the rocker arms for each cylinder. If one barely moves look at that rocker arm for any abnormalities and no bent pushrod. If those check ok then a wiped cam lobe is most likely.

When the popping occurs is the popping a steady or random cycle?

TravisF

It is a steady popping sound under acceleration. As soon as I let off the pedal, it goes away.

Brians1

I agree 100%...having same issue now and my mechanic (I threw in the towel and took to the shop as I couldn't figure it out)' he called me into the shop and cranked over the motor...I called it a banging...he called it a pop. He had me look at the #7 rockers...no movement...wiped cam, damaged lifter....either way they gotta get replaced. If these are your symptoms then your looking at a wiped cam. Only under load for the pop was my exact issue as well

augiedoggy

Curious as to what caused it? Did you install and break this cam in? Do you use the proper flat tappet oil or additives?

Brians1

I'm performing my tear down starting tomorrow....on vaca from work
As far as cause...I'm not sure the PO did not take care of it but I didn't get this until after I installed a true dual magnaflow from corvette central...made it maybe 10 miles and then boom....popping under hard acceleration.

hugie82

When I wiped my cam the 427 I was running had about 20k on it. I did have triple valve springs and with modern oil, it wiped. Same thing, down on power, then it felt like a misfire. Finally it started popping a little. Pulled the valve cover and fired the motor up and you can see the rockers barely moving compared to the rest. No valve tap or noise of any kind. Just a cam lobe with vertically no lift. My jaw dropped because this was back in the 90s and no one knew the government was screwing with the oil!

TravisF

well that got me thinking. I have read about flat tappet oil and additives along with regular high quality oil changes within this forum. I didn't use a flat tappet oil (I would need to research what that is) or any additives. Just a good quality oil and filter. Could this be the cause of the issue?

hugie82

That's a loaded question that will blow up your thread! Everyone has their own opinions on what is a good oil. Up top is a sticky on oils. If yours does measure up, then yes your oil could have caused this.

Brcmpbl

Sure you're not just hearing some detonation?

TravisF

It could be, I had a friend ask me the same question. But there has also been a decrease in power as well. I hope to take the valve covers off this weekend and take a look.

TravisF

Argh! Sounds exactly like my symptoms. Loss of power, then popping. Well I bought the car knowing that its history was a mystery. I brought the car back to life after not running for 4 years (previous owner) because I really like the car and the challenge (I'm not a mechanic). I just can't believe that all this could be caused by using the wrong oil! Back under the hood I go!

hugie82

You won't be sure until you pull the valve cover and fire it up but it's looking that way.
The good news is you get to pick out a new cam if it is depending on how many lobes are wiped out. If you have more than 2 or 3 lobes wiped, I would suggest a rebuild.

TravisF

Well because I don't know the history of the vehicle I had planned to rebuild the engine sometime in the future anyhow. It just might have to happen sooner than expected. I would like to do it myself, but that would be a huge undertaking, I've never done anything remotely close to an engine rebuild. I just bought a copy of "How to Rebuild Your Small-Block Chevy" by Vizard, David; in preparation for the job. I also talked with an engine machine shop close to home here and I was quoted 1200.00 for them to completely clean and rebuild my engine stock. All I have to do is pull it, take it to them and reinstall it when they are done. I have been told that that estimate is pretty, oddly, low.

augiedoggy

To keep it simple,
Back in the day when engines came with flat tappet cams the oil was very different. It had anti wear agents and minerals like zinc /zddp and didn't have the detergents that today's oils have. Today's oils do not have the zddp because it creates ash deposited in cat converters and additional pollution..
Also today's modern cam designs are more aggressive and that's all the more reason to diid the racing oil or additives...especially for cam breakin.