Thread: Chevy 305 knocking (with Videos inside)

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I'm new to this forum and american cars/engines in general, I hope you guys can help me

I recently bought a 87' Caprice with a completely stock 305 engine (non TBI, 146k miles on it), unfortunately it didn't even make the way home the day I picked it up...

I drove it for about two hours without any real problems, the engine hesitated a little under acceleration from time to time, but I figured it was due to not being driven for a few month during winter...

As I drove up the freeway from a fuel-stop, I put it back in overdrive and suddenly hear a silent (luckily the radio didn't work ) ticking, which seemed to be coming from the tunnel right under the dash...so my initial thought was that the transmission/ TC was getting into trouble.

I took the next exit and rolled down the window as I sneaked the car to the next possible parking spot and heard that the noise was actually really loud outside the car and the idle was way too high in Park and almost stalls when putting it back into Drive :...so I shut it off and called a tow truck.


The next day, something odd happened: I wanted to drive to car a few meters into my garage and the sound was completely gone, so I let it idle for a few minutes and the sound slowly returned, but very infrequent in neutral and completely gone in gear

Later that day, I went to fire it up again and the noise was there again, so I took quick videos:

When you stand infront of the car, the noise is actually more present on the passanger side...

https://vimeo.com/216217746

https://vimeo.com/216217833

shortly after that, the Idle began to rise again, I guess the timing and carb setup are completely off...

Haven't run the engine since then, It ran about 5 to 10 minutes total with this noise, most of it idling...

As I wrote before, I have no experience with this engines/cars, so I hope someone can point me in the right direction

And please forgive me if some of my grammar is wrong, I'm a german dude doing what I can :drool:


Thank you very much

Welcome to CHR!

The noise sounds like valve lifter to me. I would do the following:

1. Drain the oil
2. Change the filter
3. Re-fill with 5 quarts of 10w-40

Drive until it gets warm and in all likelihood, the knock may disappear.

Good Luck,
Glenn

When you drain the oil drain it over a magnet if the cam went flat it will look like it's growing a beard beacuse the cam is cast iron

Ok, I couldnt listen to your engine for some reason but I have to say I had a '83 Chevy 305 and I am not a fan, the things had smogger heads on them and pinged just by looking at them, you might check and make sure that it doesnt have that anti knock distributor from the 80's left in it, it had a sensor in a freeze plug hole and retarded and advanced the timing automatically, well it did until I yanked it out, ran better and cut out the terrible noise. Might not be your issue but dont expect much out of the 305's. Good luck and dont forget the computers where just coming into play with these motors and it wasnt always good. Matt

My ears say it's a rocker, but the videos were very short.
If it is a problem in the valve train, it may likely show up in a compression test across the cylinders.
At a minimum it'll probably give you a direction as to which cylinder(s) to begin checking.

First of all,thanks for the answers !
Alright, I removed the valve cover and checked the rockers, they were all rather tight except for one which I could slightly click from left to right, but none could be taken from the pushrod or get compressed by hand..the loosest one isn't even near the source of the sound, since it's more present at the second cylinder of that row and the loosest rocker was the last of that row...
Is there any other way to check the lifters? or should I turn the engine by hand and check the rockers with the crank/camshaft at different positions?

The engine does in fact run rough when the noise occurs , you can clearly hear it miss when listening to the exhaust... hard to describe, it almost sounds like there's a racing cam in there from time to time...

@"Matthyj"
what exactlxy do you mean by "smogger heads"? sorry if that's a stupid question, but i'm new to those engines so please forgive me
The distributor and carb look all stock and rancid:





And I also found something else:
All the "emission"-stuff got deleted by the pre owner, the metal lines on the header are cut of and crimped together on one side, on the other side the big line which feeds the smaller lines going to the cylinders got plugged with...well, I can't exactly tell whats in there...however, the engine light also got blacked out with a marker, but you can still see it lighting up in the corners..




Thanks