Hi. I have a 79 150 4X4 with a 400 and a C6. I've done the normal sort of mid range mods to the engine, intake, 4 bbl, cam, valve springs, timing set, and headers, and I just a couple months ago went through my whole trans and modified the valve body, added an extra fiber disk or two to each clutch pack, and put in a wider band.
The engine ran beautifully before and after the rebuild, and after a little breaking in, the trans also did very well. The transmission has still retained one problem though, at certain rpm ranges, it makes a sound that I would best describe as the sound that you get when you clip a playing card onto the back of a kids bike, so that when the wheel spokes hit it it makes an "engine" sound. It is a heavy sort of flapping shuffling sound. This noise appears pretty suddenly when holding at speeds between 45 and 60 mph. (If I knew the rpms I'd tell you) Going above 65 or so completely eliminates the noise, and going under 40 does the same. The noise never seemed to make anything run badly, so it didn't get very far up my to do list.
Yesterday though, I was going along, and I'm not sure exactly when it started, but noticed that what had been that sort of sliding slapping noise, was now a pretty heavy rap or knock. It also happened at idle for the first time yesterday, and now when I'm accelerating it is VERY loud, like a sledge hammer coming down on metal. I did an oil change just 2 days ago, and it's still clean, with no metal bits or anything like that visible. My transmission fluid is also still clean and smells fine.
2 other relevant pieces of info are: When I was dropping the trans, I forgot to unbolt the torque converter from the flexplate, and pulled on the trans pretty hard, I've always wondered if I may hav bent the flexplate. And, yesterday, for a whole list of other reasons, I was messing with ignition wires, and just before the knocking started last night, I was driving, the ignition wires made contact, and the starter started cranking away when I was going about 45.
My first instinct is maybe yesterday I further damaged an already wounded flexplate, but would that cause the symptoms I am experiencing?
Thanks for any help, and congratulations if you made it this far down this post.
AleX

 

Does truck shift good and run good? I once had a strange situation like this and it was a starter clearance issue. I had to shim the starter. I had a aftermarket flexplate on engine and was a clearance issue. does it do it in neutral or in gear only? if messing with torque converter hopefully didn't hurt pump in tranny. but you should see something in tranny oil pretty quick. very interesting. forgot but if you pulled on tranny and forgot bolts on converter it should of just stayed attached to flexplate and then just slid out. interesting situation.

 

I doubt it would have hurt anything pulling the converter with the engine.

 

Yes the truck still shifts and runs excellent. That's what has me so confused. Haven't tried neutral, but it does do it in park. I took the little peek cover off the bottom of the dust shield plate that goes over the trans bellhousing yesterday and while hearing the noise as the truck idled, went underneath and listened right into that little peek hole, even let the flexplate graze my finger looking for vibrations, and the sound wasn't coming from there.
I could feel the knock on the oil pan though. Why does an engine knock normally?
AleX

 

i know full well this is mucho work. but u know, in this case it might almost be worth your time to pull trans back, support block and fire just long enough to see if motor or trans. either way u go. a noise to the degree u describe is obvisiouly serious, and the more u run. more $$$$ it costs. do not misunderstand me. i know u are not a child. u rebuilt your auto. u got it going on. just trying to be supportive or help. take no offense. this hurts to say this, but it does sound like a rod a wee bit from here. i HOPE not. hence the idea split rig it up and just quick diagnose. ours was second from crank flange. sounded just like u describe. i first thought it may have been sloppy input shaft on our hi mileage t18. no such luck. you know i may be talking thru my hat. never run an auto on 400. is it possible to rebolt starter with an auto. maybe could borrow a man bell for test. reaching i know but my heart is good and i hate when this happens to a good wrench. my op and thoughts. dad

 

Need to drop oil pan. Engines/trannys are not supposed to knock at all. might be a loose rod cap and getting ready to come apart???

 

Darnitdarnitdarnit. I figured all of that, that it was something serious, but I've done pretty much the whole truck learn as you go, so when something new happens, it is pretty much for certain going to be completely new to me, and with it getting so much worse so suddenly, I thought maybe I had just made some small mistake. After a year of working on this thing basically eeevery single day though, and after rebuilding the entire top half of the engine, I'll admit I've never touched a pan bolt once, so I have no reason to think that something isn't just about to explode. I'll get underneath and see what's going on I guess, ugggggg, but thanks guys, AleX.

 

Everyone, I've taken up oil painting! My first painting was myself! No not a self portrait, i mean I literally painted myself with oil... I took the pan off, had my brother crank the engine over for a second at a time while I was underneath, and although I don't know exactly where the knock is coming from, I now know that it is from somewhere in the bottom half of the engine (cam down). If anyone has any advice as to how exactly I should isolate the knock any further than that, I would appreciate it.
When I was underneath though, I discovered some very interesting things. First, I have a 1971 400! The good year with the 9.0-1 flat top pistons! D1AE was stamped on everything down there. My heads are D5AE though, meaning anywhere from 75-80 right? How can you tell 4V heads from 2V?
Next, although I did an oil change less than a week ago, I had never actually taken the pan off, so I didn't know what type of large debris might be waiting for me in there. What I found though, blew me away, copper. Quarter to half inch flakes, about paper thick, of bright shiny copper. How in the world could that have gotten in there?
Finally, every time I'd have my brother start the engine for a second, as soon as he would turn it off, I noticed that a white oil would come dripping down from the inside of the block, and mixing with the dark used oil. It wasn't water/coolant, it was an oil, it mixed perfectly with the dark oil, but where the heck could it have come from? Maybe it was just oil mixed with tiny air bubbles since the pan was off?
I'm excited about some of this, extremely disheartened by other parts (how loud the knock is with no pan), and very curious but just baffled by the rest. If you're reading this and know the answers to any of my questions, please help me out. I want my truck back, and I want to get it right, finally, AleX.

 

So you:

--did top end work, but never touched the bottom?

--hear a knock like a sledge hammer on metal?

--find big flakes of copper in the pan?

Next step, pull rod caps off. Keep track, as they should go back on the same rod.

I think you will find a destroyed bearing and damaged crankshaft and rod.

It has to come all the way apart to fix that. That means you might as well check the bore and if needed, bore it and put new pistons in, a cam, cam bearings, oil pump, etc etc....

Don't forget to get the rod resized.

Oh, almost forgot. The "white oil". Tell me, is there a separate reservoir for "white oil" in your engine? Of course not. You may have a cracked block and you are seeing an oil/water/coolant mix dripping. Have the block checked before any machine work is done.

 

As 85e mentioned check the rods.Look for a discolored cap,extruded metal hanging out of the cap,excessive play either up and down or side to side.Turn the engine over with a bar and socket and watch the travel and movement of the rods.If you have flakes and debris that size,there is a major failure in there.While you are down there,try to track the entry point of the coolant into the crankcase.

 

You could have pulled each plug wire off one by one when it was running to see if you could have isolated the knock to a particular cylinder.

 

85, thank you for the advice about the caps, I'll try that now and tell you what I find, but as to the rest, especially the part about the white oil, there's no need to be condescending. Ask me once and I'll tell you that I'm new at this. I've had 2 old Ford trucks, and done what I can to learn everything I can about each of them, but I am no trained mechanic, I'm learning as I go. I know quite well that there is no white oil reservoir on my truck, but what I saw last night was best described as white oil, and when I really have no idea what something is, rather than guessing, I try to describe it to someone as well as possible, and the best description I can give you is that it appeared to be a white oil. Furthermore, I asked the mechanic at the place I work today, and he said that the white stuff could be coolant, as it turns milky when it mixes with hot oil, but that it could just as easily be thick oil frothing up because of a cold start, and that he has seen exactly this before on old Ford engines, so I may not even be that sunk.
Next, mask, the debris in the pan was copper, and I know of no parts in the engine that have even a small amount of pure copper in them, and there was NO other metal in the pan, so about all that, I'm still very confused.
Mark a., thank you for the idea, I may still try that.
Thank you for the help everyone, I'll keep updating, but if you're going to snap an answer at me then I'd prefer you just kept quiet. I ask alot of questions for a reason, I'm a very curious person and I'm trying to learn. Take all my questions as a sign of respect, I'm interested in the things you know, and I trust your knowledge enough to ask you to pass it on so that I can benefit from it. I will be ashamed of myself if I ever talk down to someone who is doing me the honor of asking for my help.
AleX

 

Well there's some pretty heavy storms going outside right now, so I had to come in before I could remove any of the caps, but I did have a chance to do a few things. I tried removing one plug at a time, but it knocked through every single one. That does tell me conclusively that it isn't just pinging I guess, but I already figured that. Also though, after having the engine running for at least a few seconds, and now thinking to look for the exact source of the white stuff, I found that it is coming individually from almost every cylinder. It drips slowly along the lowest path on the sleeve wall below each piston, and then collects on the lowest points on both sides of the engine (the main bearing bolt heads). The fact that it is happening on both sides of the engine, and coming from multiple cylinders (if not all of them) on each side, tells me that it is highly unlikely that it is coolant/water. Since the intake is dry, I would have to have blown the head gaskets on both sides and around each cylinder, or cracked the head or the block in a similar way for water to leak into every single cylinder, and I'd also have to have pretty much completely nonfunctioning piston rings all around for that much fluid to leak from the combustion chamber to the cylinder sleeves anyway, right?
Tell me if any of this is wrong, but I think I'm back to looking for the source of only the knock.

 

Well, I found the source of the knock. The very frontmost connecting rod was loose to the touch. I was really suprised that it was that simple. The second from the rearmost rod is also loose on the crank just very slightly, the front one was wiggly though, some real play. I took off the 2 nuts, slid off the cap, and found the bearing surfaces of the cap, rod, and crank, all relatively OK. They weren't mirror finish, the grooves were just big enough that you could feel them with your fingernail, but not horrible. I know that they really should be mirror finish though, and I also have only heard this knock for about the last 30 miles, and it came on very suddenly.
All that said, my question now is, what do I do? (Secured the cap back on, wasn't just loose, still knocks) I know not to abuse the engine now, but do I keep driving it? What do I fix if not? Everything else looks and feels fine. Can I change out just one rod? Can I keep that piston? How much is a new crank? Or is all of that just dumb, and should I really just go with a total rebuild, or a whole new engine?
Any thoughts anyone?
AleX

 

Complete rebuild, including either a new or turned crank. The rods must be resized, and that means the pistons come out. You would not want to put the old pistons and rings back in the motor after all the work and money you have/will have in it.

Sorry about the previous impression, you should see the messages when I try to be an a hole.

Your block should not be one with the dreaded block cracks:

Rumors & Myths

So the drippage from multiple cylinders makes me want to say head gasket.

I wish it were different, but with that kind of damage and the other questions, a fresh start on the motor is the only way to have a reliable engine.

Good luck with it.

You can find several links about your engine with a simple search like "351m-400" etc.