New project with a knock, what do you think?

Picked up a new project, a 99' Prerunner, 3.4l, auto. Got it for cheap and am doing a 4wd conversion on it. However, I need to address a knock it has, it sounds high to me like it could be in the valvetrain but I can't think of anything in the valvetrain in these dohc trucks that would cause such a racket. What do you guys think? Rod knock and yank it and rebuild it or could it be in the valvetrain? Here is the link to the video: https://youtube.com/shorts/gGZLqfFCte0?feature=share

 

If I had to guess, it would be in the head. Pull the valve covers. Rotate the engine with hand tools and look/feel for any loose valves or broken valve train.

Also can perform a compression test. That might pinpoint a broken valve.

 

Yep a compression test could save a lot of time.

 

Rocker arm or cam lobe is worn

 

A flatted lobe is all I could really think of. No rocker arms in these bad boys.

 

ive never opened a totoya up. Good info.

 

Sounds like a belt tensioner to me.

 

This was my Sienna with a bad timing belt tensioner. It sounded very much like a rod but Toyotas don't roll bearings in the top end. If it did there would prob. be a rod hanging out the case. This also sounds like a huge exhaust leak but it wasn't. I replaced the (counterfeit Ebay) tensioner after 20K miles and it was happy again.

 

Ok, so finally got to tear into the truck and the first thing I did was pull #6 sparkplug and this is what I see. Began pulling everything off to get access to timing junk so I can pull the head. Anyone seen anything like this before?

 

I have, long time ago. Ford F150 with 300 straight 6. Oil change tech dropped a washer down the carb when changing air filter.
2 miles away, it started knocking.
Spent the weekend pulling the head to retrieve it. Had some nice knicks on the piston too.
Oil change guys paid the bill for the parts I bought.
Prolly not what you are experiencing though.

 

Your engine Ingested some FOD thru the throttle body , either a screw or bolt , The closed plug gap is a dead giveaway . The sound you're hearing is something inside the cylinder being pounded into the combustion chamber of the cylinder head . At most that combustion chamber is trashed as is the cylinder wall and top of the piston

 

The most common item that gets sucked into a cylinder are throttle plate screws . Such a tiny screw can cause alot of carnage , I've even seen it punch a hole in a piston

 

Oof, I wonder if I would be better off finding a replacement engine.

 

I think it's worth pulling the head and taking a picture for the rest of us.
It may be salvageable.

 

Do yourself a favor before you get way too deep, order a bore scope off Amazon. You can get an idea without tearing it completely apart. If the object is small enough, you may be able to retrieve it with the magnetic tip. If that is the case, do compression and leak down test, if it is all good, let it ride. It could save you some money now, you just know it may be an issue later.

 

Ugggh, Hate to say for your sake, that looks like everyone is prob. right and you have a foreign object inside.
Hate to say for my sake that I lost a bet and owe a beer.
No, I don't want to trade places. Have been in the spot before though. Carburetor days were notorious for it.

edit: I also could be wrong in respect to a bearing. If there a bit of slack in the big end of the rod it will let the piston come up that small amount needed to smack the plug every rev. Seems like it would have a heavy knock in addition to the metallic rap of hitting the plug though.

 

Could you be out of time? This just doesn't sound like a nut or bad bearing. If a tensioner failed a plug electrode just might be within reach of the piston, I don't know.

Look inside before pulling head.

 

Autozone rents those borescopes so Ill grab one and have a look. Ill have a look and tear down timing stuff on the front to check. Will update with some pics in the next few days, thanks fellas.

 

I just can't see it. Both electrodes bent and porcelain not broke? Strange...strange things happen though.

 

Welp, I'd say she's chooched. Anyone know if these engines are sleeved? There is some scoring on the cylinder walls that'll catch a nail but its not insane. A relative who does all the Toyota heads around is going to swing by and have a look, I have no doubt the head is toast. Local place can get a long block with 140ishk on it for $1750. Might be the way to go.