Engine Knock

A knock has slowly become apparent on my motor. I had known about a possible rod knock already, but that only seemed to happen on a cold start up and would disappear right after the motor started up, also sounded different.

This noise sounds like it's coming from lower and is only audible when I am giving it gas… Ive attached a video for some reference. What do you guys think? Am I pretty much screwed?

I removed the spark plug wires one at a time to see if I could isolate the noise to one cylinder, but nothing changed.

cant see or hear private vidio

m1d

Whoops, try it now

Scotty,
That defiantly sounds like a rod knocking to me. You should not drive it anymore till you replace the rod bearings & main bearings. I wouldn't even suggest that you crank it up anymore!

Had a feeling it might be serious. What are my options?

Can I drop the oil pan and change these without dropping the motor, or is it pretty much necessary to drop the motor? At that point do I might as well rebuild the entire motor since it's out? Or buy a fully rebuilt crate motor for $1600?

You can support the engine from above and drop the motor mount and pan. Then individually change out the rod bearings from below. For starters tho, just Check them one ata time and see what the story is. If the crank is toast then yeah its time for a new or rebuilt engine. You might be okay if it isnt to bad to just slip in some new bearings, but it is only going to buy you some time to come up with a better engine. This is super Po' Boy stuff but you'd only be into it for the bearings pan gasket and an oil change for now. If you have to do machine shop work and replace/rework all the moving parts, that 1600 crate doesnt sound to bad. JM2C

Just an add on here, normally pulling a plug wire will quiet a rod knock somewhat. If you can do a compression test also might be helpful. I couldnt tell if it had a miss or not from the video.

I would just pull the engine & do a complete rebuild on it. You can get a complete master rebuild kit from Northern Auto Parts for $305 & it will cost around $300-$400 to get the block cleaned cam bearings installed, cylinders bored & the head re worked. As nice of a van as you have it will be well worth doing a rebuild on the engine! Just what ever you do don't keep running the engine or you will be replacing the whole engine.

If I can manage to save up and get a crate motor that's basically ready to drop in, I may go that route.

If I can convince Don to help me tackle a rebuild, maybe I will try it
My main hesitation is that I don't have a garage to work in and keep any half assembled parts etc.

Its hard to diagnose a problem by listening to a video but I think that it's a rod knocking. Maybe if Don can check it out you will get a better opinion on which route to take. You could probaly get by with new rod bearings & main bearings. Which can be replaced with dropping the oil pan. I would want to keep the original engine if possible.

replaced my rods before nats. did it while in van. the crossmember comes out completely and bearings are pretty easy. mine wasnt knocking, it just wouldnt keep oil preasure. if your crank is scored, probably not worth the time. i have heard of people cleaning them up with emery cloth but i never have, or will.

I guess I should check out what's going on in there before I drop a bunch of money, then decide what to do. If everything else looks ok, maybe replacing those bearings will hold me over until I can save up for a new motor...

I didn't think about the torque converter bolts possibly being loose. That's a good first start to check. I had a 1980 Chevy silverado that I thought for sure had a rod knocking & it turned out being almost all of the torque converter bolts were loose & one of them had came out.

I will check that tomorrow…the knocking did seem like it was coming from down low when I listened from underneath the van, so that could be a possibility (fingers crossed).

Definitely count me in for the van show in El Cajon. I also need to at least be able to drive it down the hill to the Tiki Oasis car show in August!

Good Luck! Hopefully it will turn out to be the torque converter bolts loose.

don't go throwing away good money. Further diagnosis is warranted here.

I agree to checking the torque converter bolts and also look very carfully all over the flex plate for a crack, especialy around the crank to flex plate bolts and check them for tightness too. You will have to undo the torque converter and slide it back to check the crank bolts.

However that sound is comming at cam shaft speed and has the eractict inconsistancy the valve train can have. Since you think it is a lower end sound it could very well be a sticking or colapsing lifter.

Gat a stethescope or use a long bar to listen on the block at the bottom of the side covers at each lifter location.

Judging by the soumd, its speed and eratic behaivor, if it is to do with the botton end it would have to be a cracked piston skirt to be at that speed but if it is that it should disapere with the plug wire pulled.

M1d

That sounds like a good pre plan. Is that your original motor?

Whatever ends up being the problem, it will be nice to know everything is in working order so I can put some more miles on my van.

Well, bad news, those bolts are tight. Looks like the problem lies elsewhere.