Rod knock? (Watch video at post #6)

Hey guys. I have been having this issue lately. I get occasional carburetor backfire and instant loss of power. it actually became worse today using some seafoam(1/4 only) and there's a slight knocking noise. Could seafoam might have caused a damage? 302 engine with 4 barrel edelbrock. Thanks in advance.

I would check your timing first of all. Your backfire is most likely the spark plug lighting off while the intake valve is open with some fuel in the intake manifold.

Do you have the book/manual for the Edelbrock? If not, grab a copy and make sure the carb is tuned properly - if it's rich, too much fuel can help the backfire along as well.

It's definitely rich, it literally drinks gas and also PO did a messy job running the wires, they are touching and overlapping each other, I think I have to rerun them also. So rerun the wires and adjust the carb?

Don't ignore the ignition coil and ignition condensor. I've seen both cause lack of power and cause intermit backfire

It's definitely rich, it literally drinks gas and also PO did a messy job running the wires, they are touching and overlapping each other, I think I have to rerun them also. So rerun the wires and adjust the carb?

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That should definitely help. ::thumb::

Spark plug wire cross-talk can also cause back firing. Electricity is lazy - it always takes the path of least resistance.

Once you get that done, still check the timing, as well as the coil, as judge said. If you still have points, you'll want to check the points 'timing' as well.

Anything firing while the intake valve is open will create the backfire. A weak coil or condenser will take longer to fire, which can screw up timing as well.

Alright guys! Found out the issue. I did the spark plugs the other day and buy mistake, I forgot where the first two went so I ended up installing them wrong. Backfire went away immediately as soon as I switched those back to where they belong. But now I think I got a huge problem. While it was backfiring and stalling, I kept revving and I believe I caused something catastrophic. I have a knocking noise now. Could anyone identify this? Here's the video:

http://youtu.be/QjeUm8zkYks

change the oil asap........

change the oil asap........

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I was thinking that, change the oil with something thicker like 10w40 and see if it gets quieter.

Drain your oil and check the oil for metal particles, if there's metal in there, then you have more than likely bearing problems. If the oil is not real metallic, then cut up the filter and check for metal particles. I'm not real good on hearing things properly on a computer (same as when people would call the shop revving their engines over the phone asking what I thought the problem was) but that sounds to me like a big end bearing gone, more than likely due to keep running the engine with a backfiring problem, which in turn has probably put extra load on the bearings from not firing properly and hammered them. Seen some crazy stuff with engines over the years, but when sounds like that are present, it's usually not a good outcome. Anyway hope it's not too bad of an outcome and fairly easy and straightforward fix for you.

I vote rod bearing by the sound, hope I'm wrong.

I've heard my share of rod knocks and was only fooled one time

turned out to be a piston lost its skirt.

Hard to tell for sure from that video

Thanks. It was perfect before the backfire issue and I didn't even beat on it except for a few high revs while it was back firing. If backfiring wouldn't cause that, I'm sure it can't be anything serious since I didn't really beat on it but like you said, you never know, it's an old motor and things happen. Hopefully nothing major

Just drained oil and that's all I found. Kind of looks like thin kanthal wire bits. I ripped apart the oil filter too but there is nothing in it except for lots of gunk and carbon bits(literally 5 miles since oil change)Am I screwed?

By the looks of that, good chance of the big end bearing being hammered out, also remove the oil filter and cut it up and have a look inside to see what's inside. At this stage it's not looking real good.

By the looks of that, good chance of the big end bearing being hammered out, also remove the oil filter and cut it up and have a look inside to see what's inside. At this stage it's not looking real good.

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Nothing in the oil filter.

Sure looks like wire wheel pieces. There's more where those came from.

Rod knock or piston skirt like Rocket said is my opinion, too.

A change in oil viscosity won't fix a thing.

Either way, it will probably warrant dropping the pan for some pre surgery exploring.

You may find this inside:

Yup they are from the wire wheel. I forgot I used the wire wheel the same day and bits from it fell into the oil bucket. So there's no damage yet I guess. Should I just replace the bearings dropping the oil pan?

Hi,

the sound of your video remembered me of my damaged piston rod bearing last year. It sounded exactly like this - a very strong sound from inside. It came suddenly but you could have heard it before very very latent - difficult by all the noises of our cars.

After hearing that sound I drove 20 miles back home - the worst trip in my life accompanied by that hard knocking. I didn't know what it was back then but only that it would be something bad. My buddy and me hoped that it was something easier and stripped the engine part for part. Waterpump bearing - no. Headers and their gaskets - no. Petrol pump - no. Spark plug wires and other ignition elements - no. Lifters and valves - no. And so on...

The result: one bearing half slided under the other and caused that sound. So the piston rod had enough vertical clearance to knock against the crankshaft and caused an elliptical cut to the crank bearing of this piston. Fortunately the piston didn't touch the valves of the head but it was very close. The end of story was a complete engine rebuilt from ground with an other good old crankshaft and a piston rod. You can follow on my restauration thread...

Flip the oil pan and check the rods for vertical clearance - you will feel it clearly if there is something like I mentioned before...

Wish you all the best,

Tim

Hey Tim. Thanks for the input. Do you think it's possible to just replace the bearings right from under without pulling the motor. Car ran like 5 mins since it started knocking so I might be lucky it didn't cause major harm yet. If I'm gonna end up doing a complete engine rebuild, I would pretty much rather swap it with a cammed 351w.

Do you think it's possible to just replace the bearings right from under without pulling the motor. Car ran like 5 mins since it started knocking so I might be lucky it didn't cause major harm yet.

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Hey!

Yes, with a little skill that's possible - but you have to turn the crankshaft. And look exactly at the crankshaft bearings and the piston rod if there is too much clearance before you add some new bearings...

Tim