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93 engine knock... V6

scoodidabop

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So I bought a 93 and I'm working to covert it into a Jurassic Park tour vehicle. The previous owner put a donor motor in it about 5 years ago and now it's developed a knock. I only paid a few hundred bucks for the whole truck anyway and it's in nice cosmetic condition and has loads of new parts.

Anyway I looked at a 94 motor donor (craigslist, $150) and it sounded a little tired but ran ok. I worry about compatibility since I noticed my 93 doesn't have the extra emissions stuff that was used on the 94 motor... and other things like the belt tension pulley is in a different spot. Should I pass on it? Junkyard is my next option but I've never pulled a motor from there before so I'm not sure if that's a great option.

Thoughts? Thanks fellas!
 


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Anime

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What sort of knock does it have? Sometimes 4.0L OHVs that "knock" under load actually just have minor issues like clogged fuel injectors. Bad gas did this to mine and it knocked when pushed until a few weeks/months of top tier gas and fuel injector cleaner took care of it. It might also just have vacuum or air leaks or need general maintenance. Sometimes the valvetrain clatter can be mistaken for knock as well, that's just a common thing with all OHVs, the stock rocker arms need to be replaced to fix that, a different engine with stock rockers will just develop the same noises, eventually.

The 94 motor is a drop-in fit, the different pulley is probably the better one, Ford recalled the old pulley design on the 91-92 that some early 93's had, so the smooth pulley with the round dial-type tensioner is what you want, not the alloy lever type with the ribbed plastic pulley. You can install the motor and keep the stuff from your 93, so it stays non-EGR.

Maybe make a $100 cash offer on the motor. Might be worth it just to have the spare parts, though maybe you can get a parts Explorer for just a few hundred as well. Personally I'd look into whats causing the noise on the current motor, especially if you think it's in better shape than the one you looked at.
 




scoodidabop

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I pulled the valve cover off on the side that seemed louder (driver's side) and ran the motor for a bit. All the valves seem to be moving freely (as far as I can see) and the rocker arms are moving smoothly. My brother in-law is very motor "savvy" and took a look at it. He couldn't tell where the knock was coming from though... He had me hit the key a few times to turn the motor and felt the shape of the pushrods; they checked out straight as far as he could tell.

I gave the motor the old Seafoam treatment as well; some in the gas and some poured into the vacuum line while running. It blew plumes of white smoke but never cleared the knock. Injectors are fairly new along with new spark plugs and spark plug wires. Drove it around my cul-de-sac a few times and there are no signs of "power" loss either. Just a frikkin clattery knock. ARG! It doesn't help that the guy with the donor engine is a major hoarder... his home being is a severe state of disrepair and disgust casts the condition of his offerings in a negative light.

Should I post a video of the knock? I've already started taking things apart but could have everything back in and running within an hour so. It's just such a shame since the motor has already been swapped once... would be nice if the issue could be a identified at the very least, then an educated assessment could be made about what to do with it. Hoping it's not a rod knock but who knows... :/
 




Turdle

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Does this replacement engine have the egr tube? could it be leaking? An exhaust leak from near the heads sounds like a knock-
 




scoodidabop

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Does this replacement engine have the egr tube? could it be leaking? An exhaust leak from near the heads sounds like a knock-

Negative. No EGR on this one... Not sure if my 93 was early enough to miss the EGR inclusion but the donor they installed does not have it.
 




Anime

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You ran the motor with the valve cover off? Did engine oil not fly all over the place and coat the engine compartment on that side and underneath the hood? If not, maybe the oil level is low and the noise is from lack of lubrication.

Your brother-in-law sounds like a know-it-all who probably doesn't know as much as he wants you to believe he does. You can't "feel" if pushrods are straight, especially if they're still IN an engine. The valves and rocker arms will still move freely, the issue with the stock rockers is that the metal is soft and they develop indentations, which eventally leads them to develop a gap, that causes valve clatter under load. You won't see this visually unless you look at the engine with the valve cover off while driving the vehicle - not very safe.

You can post a video of the motor running and making the noise to get some opinions on what it is, sure, but keep in mind most videos have poor sound, and so what you actually hear in person won't always be easily heard in a video, especially for those with smaller computer speakers.
 




scoodidabop

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You ran the motor with the valve cover off? Did engine oil not fly all over the place and coat the engine compartment on that side and underneath the hood? If not, maybe the oil level is low and the noise is from lack of lubrication.

Yeah I ran it that way... sputtered a bit a dripped a bit. I didn't run it for an extended period of time so the mess was minimal. Oil level is within spec and pressure gauge is showing normal.

Your brother-in-law sounds like a know-it-all who probably doesn't know as much as he wants you to believe he does. You can't "feel" if pushrods are straight, especially if they're still IN an engine. The valves and rocker arms will still move freely, the issue with the stock rockers is that the metal is soft and they develop indentations, which eventally leads them to develop a gap, that causes valve clatter under load. You won't see this visually unless you look at the engine with the valve cover off while driving the vehicle - not very safe.

Hey man, that's not very cool to make assumptions about my brother in law based on what I said. I'm the "engine illiterate" one here, not him. He really does know his stuff and half of what he said went over my head so much that I have trouble recalling it correctly. He's passionate about motors and has been rebuilding them for a very long time so I trust his opinions. Anyway, he did his best to help me assess the issue and felt the pushrods in their various positions to see if they were grossly bent or not (I believe). His advice was to pull the head to check then let him take a look at it again. The head is coming off today but I've asked the guy selling the motor to hold it for me until the weekend.


You can post a video of the motor running and making the noise to get some opinions on what it is, sure, but keep in mind most videos have poor sound, and so what you actually hear in person won't always be easily heard in a video, especially for those with smaller computer speakers.

I'll get everything back in and make a video... might even use a quality condenser microphone to capture the sound since I'm sure my camera won't do it justice. Look for the video post in a bit but I'm not optimistic about how clear it will illustrate the issue.

Side note; my fan clutch bolt is giving me the hardest freaking time. The shop that replaced the fan clutch (about a year ago) buggered up the bolt just enough to make it IMPOSSIBLE to grab with the special tool. I bought a few different sized pipe wrenches to get it off but they're all too wide... moving on to my largest set of vice grips and hoping for the best. Any tips on getting that thing off? Fan shroud reads "right hand thread" so I'm certain I'm turning the bolt the right way... loaded it up with PB Blaster last night so I think that may help my cause.

Thanks a ton fellas! Check back soon for that vid....
 




scoodidabop

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Not sure of the "double post" rules or anything here so I hope it's ok that I'm posting again so soon... if not feel free to combine my posts moderator.

Got it back together (for the most part. Didn't tighten a line on the tranny cooler so I lost a few drips of fluid) and ran it for a little over a minute to record the knock. Here's the video;

http://youtu.be/4bptDqMcPpg

You'll notice my tickled disposition since I've forgotten how comically nasty the knocking really is. Not feeling like it's a simple fix really but that's ok. The video may help identify the problem but no big deal if it doesn't.

Let me know what you think.
 




Masterd

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Im going to be as optimistic as possible after hearing that noise and guess bent pushrod(s).
 




arco777

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You can tell whether a knock is valvetrain or bottom end related by the speed at which it occurs. I believe that a valvetrain noise occurs at 1/2 of engine speed. Use a mechanic's stethoscope to pinpoint the knock's location. Supposedly an ear to a screwdriver works the same way, but I've never had good luck with that. Mechanic's stethoscope works great for me.

If you truly have a lower end knock, repairing/rebuilding the bottom end the right way is going to cost more than a used donor motor in most cases. A top end (valvetrain) noise could be fixed with junkyard valvetrain components and be repaired with the engine in the vehicle.

After listening to your video, I'm thinking valvetrain. Possibly fixable! Fortunately you can pull the heads and (relatively) easily replace everything down to and including the lifters if need be.
 




arco777

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Watching your video, In 10 seconds of idle time, I count an average of 60 "knocks". I did this count almost a dozen times. That works out to 360 "knocks" per minute.

Assuming an idle speed of 600-700 RPM, which is standard for these trucks, that is approximately half of idle speed. I would bet that is valvetrain noise. Camshaft spins half the speed of the crankshaft.
 




scoodidabop

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Well alrighty then!! That's nice to hear that it might be valvetrain related based on the noise. I'll pull the heads and check em out... especially the head on the driver's side. Will it do my any good to post pictures of the various head components?
 




Roadrunner777

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Peanut Gallery Reporting In!

Yeah, this engine has a reputation for soft rocker arms, leading to valvetrain noise. Check other threads. There are kits available for this problem

Yeah, some knock is normal for this engine, says so in the manual. Mine knocks under load, regardless of of gas grade, use or non-use of additives, so forth. I tried seafoam and all the other fixes. It's an iron engine, not that big of a deal I guess, I have driven it for years like this.
 




scoodidabop

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Got the driver's side head pulled. I'm no expert on this stuff but here's everything I can assess, plus one seemly big issue with one of the pistons;

All rocker arms seat firmly against pushrods and valves. Rocker arms look good when removed. No perceivable wear on the arms where the make contact with the pushrods or valves.

Pushrods all look straight. Rolled them on a flat surface (like a pool cue!) and had no perceivable bend. All ends are uniform and length of rods seems the same. Sorted and marked for reinstallation.

Valves all pretty clean on surface and have uniform residue. All can be depressed be and and none are "stuck". Area surrounding valve heads (combustion area) all have uniform residue (none obviously more black or yucky).

Okay. So far so good right? I though "hmm... if it's a rod bearing shouldn't one of these pistons be loose or something?" So I pressed down on each of them with my thumb and the piston furthest from the radiator sank down about 1/4" with a "thunk". Other pistons stayed firmly in place. "Crap. That might be the problem".

Does that indicate a rod bearing issue or is a little "play" normal? For all I know the other 2 pistons could've very well been seated down already and this third one only became seated the same way when I pressed on it.

Anyway that's where I'm at now. The passenger side head comes out in the morning for inspection. Any guidance and feedback is, as always, much appreciated fellas.

Thanks!
 




mr cribb

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The rattle at the end of your video is the guts of your cat converter.... mine did it until I took care of the loose stuff floating around the inside.

It also sounded like you have an exhaust gasket issue.
 




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