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Possible knock - pucker factor 5

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TheBirdman View Drop Down
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    Posted: Dec/03/2018 at 11:21am
Well, I may have a problem. Lets just jump right in. Ive got an 83 eagle wagon that I swapped a 4.0 into last fall, and transplanted the 4.2 accessory drive, intake, carb, and ignition onto it. A few month later I put a MC2100 on it, and last summer I put a skip white HEI into it, with a crane vacuum advance. I recurved the dizzy a bit and had it running great in the summertime. Then winter rolls around, in the land of the snow, home of 10 degrees F. The car starts acting a little cold blooded. For the first 3 minutes of running, till the coolant got to 130F or so, it would stumble off idle and occasionally die at stoplights. Now I get it, 35 year old car, carberator, ect, I should have just let well enough alone, but I couldnt help but remember that with the carter and ford ignition it started and ran just dandy in the cold, almost no warmup needed at all. The downside of the combo being, it had no power. So I set off to tweak the carb and hei to see if I can get it running better in the cold. Part of the trial and error process was to crank up the advance limiting cam on the crane unit to take around 10 degrees of vacuum advance out. I made the change, and set the idle timing back to 11, but it just ran like total junk. Misfiring, chugging, nasty. After more head-scratching, cursing, and investigation, I found that I had set up the HEI with the rotor on 180* backwards. I dont think that really would have caused any problems on its own, but there was a tab on the rotor to keep that from happening, and I had screwed it down on top of the tab, thus making the rotor sit cockeyed.
But lets back up a little. When I was reassembling the dizzy after screwing with the vacuum advance, I put the thing back together and it wouldnt start. Wierd, turned out I left the rotor out. I took the cap back off to put the rotor back on, and seeing the tab, put it on the "correct" way. Since it was set up backwards originally, when I cranked it after this it popped and backfires a couple times. Knowing what the problem was, I took the rotor out again, cut down the tab so it would sit flush, and stuck it back on how it was originally set up. After that it run just fine, no misfiring. The problem is...

knock knock knock knock
I took this video about 30 seconds after first hearing it, and by the time my phone was out and recording, the noise was a little quieter, probably 75% of the original sound. It quieted down to probably 30-40% after running a minute, and while it was idling I pulled each spark plug boot to see if I could get the noise to change, but didnt get any noticeable change. Now this was late last night, andId had enough, so I called it quits. This morning I popped the flexplate inspection cover off to see if the flexplate bolts were loose, and they were all tight as a drum. I started it up to hear if it got louder when cold again, but it was pretty quiet, Id almost consider it a tick rather than a knock now. heck, if I didnt know what I was listening for, I might not be able to pick it out of the background normal bottom end noise. It doesnt really get any louder or quieter with revving or rpm changes.
Im going to check the spark plugs for signs of detonation, check the oil for sparklies, and do a compression test later today. Ive also got a buddy with a stethoscope coming over so we can see if we can find where exactly its coming from. Anything else I should check? Any ideas of what it could be?
 My first thought was that the backfiring while the rotor was backwards bent a rod or spun a bearing, but Ive never seen one of those type of noises get quieter like this. At the same time, Ive never heard a lifter sound as bad as it was initially, and I cant think of any reason why a lifter would collapse after a backfire. The 4.0 motor had around 100k miles on it when it arrived at the junkyard, and it passed a compression test and leakdown test with flying colors last year.
1983 Eagle Wagon
4.0 from 93 cherokee
motorcraft 2100
skip white hei
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tufcj View Drop Down
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Post Options Post Options   Thanks (2) Thanks(2)   Quote tufcj Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 1:00pm
Sounds like a rocker or lifter to me.  Too quiet/fast to be a rod.  I'd pull the valve cover before going into the engine.

Bob
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 1:14pm
Sticky lifter.
1971 Javelin SST
American 304 2v | FMX | AM20-3.31

1983 American Limited
Jeep 4(.7)L S-MPFI | 1982 NWC T-5M (4.03/.76) | Dana30IFS/35-2.72
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 2:40pm
Originally posted by tufcj tufcj wrote:

Sounds like a rocker or lifter to me.  Too quiet/fast to be a rod.  I'd pull the valve cover before going into the engine.

Bob
tufcj


I'm with Bob on this too - the knock is too 'light' sounding to be a rod or something deep down in the motor. That it happened at the same time you were dealing with the distributor is probably just a case of coincidence, and not the cause of it. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheBirdman Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 3:43pm
I agree it sounds way light for a rod, but that is one heck of a coincidence. If I dont find anything wrong in its biopsy today, Ill have the valve cover off in the next couple of days to put new seals in, I can inspaect things in there. Maybe Ill send an oil sample into blackstone to reassure myself.
1983 Eagle Wagon
4.0 from 93 cherokee
motorcraft 2100
skip white hei
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fluffy73 Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 7:07pm
Agree with all those above me. Sticky/Lazy/Leaky lifter. Worst case scenario, it's stopped rotating and is biting into the cam.   Pull the rocker cover and check for slack.

Not sure if there's an inherent design flaw or it simply stems from lack of maintenance, but I've never owned an AMC six that didn't need lifters.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 8:25pm
I would first pull the valve cover, examine the pushrods, turn the engine over by socket wrench OR disconnect the distributor and blip the starter while watching the rockers for lack of movement. I can't really tell the location since I'm on my old monitor and using junk speakers for the first time in forever but it sounds like it could be 5 or 6.
1971 Javelin SST
American 304 2v | FMX | AM20-3.31

1983 American Limited
Jeep 4(.7)L S-MPFI | 1982 NWC T-5M (4.03/.76) | Dana30IFS/35-2.72
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheBirdman Quote  Post ReplyReply Direct Link To This Post Posted: Dec/03/2018 at 9:20pm
Well hey, good news and bad news.

Good news is the knock went away completely, couldnt even hear any ticking with the stethoscope. Engine ran pretty much perfect too, it idled the smoothest it has in a good while, I bet the cockeyed rotor was screwing it up.

Bad news is there is enough bearing material in the oil that I can wave a magnet over it and watch the magnetic fields in the sparkles. Its actually kinda pretty.

We are thinking it was already on its way out before this. I only put the magnetic drain plug in on the last oil change, so I wouldnt have noticed it, and I think I recall seeing the wavy patterns in the oil before, and not looking hard enough to see that it was metal. Im going to send a blackstone sample in just for kicks and giggles. Anyone wanna take bets on how many hundreds of times over the limit the copper levels are?

I suppose Ill wait a few days and a few day's beers until I decide what to do next. Could pull it out, put new bearings in, and hope that was the only problem. Could fill it with 15w40 and lucas and get a few more drives out of it in the meantime. Could find another 4.0, transplant all this eagle junk onto it, and whack it back in. Wouldnt be near as hard as the first time. I still have the 4.2 crank and rods, so I could save up for a little machine work and make a 4.6 stroker.

Maybe Ill just park it outside for the winter and focus on other problems for a while. My crown vic would enjoy the warm garage space.
1983 Eagle Wagon
4.0 from 93 cherokee
motorcraft 2100
skip white hei
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Post Options Post Options   Thanks (0) Thanks(0)   Quote DaemonForce Quote  Post ReplyReply Direct Link To This Post Posted: Dec/04/2018 at 12:31am
I can say based on where you're at, you have a good pick of the litter when it comes to 4.0 donors and that should be really easy but you're nowhere near ready to do the stroker build until you're absolutely sure you're not going to need so much garage space. Also, make sure you setup a kickback for that process and I would estimate somewhere in the $1500-2000 range. There's nothing bad or embarrassing about the stroker but the thing with speed shops and parts is that the stroker project can get real stupid real fast. The odd geometry issues with the Eagle multiplies this difficulty a few times over. Plan out your purchases if you're really going to do that. Thank God I did.
1971 Javelin SST
American 304 2v | FMX | AM20-3.31

1983 American Limited
Jeep 4(.7)L S-MPFI | 1982 NWC T-5M (4.03/.76) | Dana30IFS/35-2.72
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Post Options Post Options   Thanks (0) Thanks(0)   Quote farna Quote  Post ReplyReply Direct Link To This Post Posted: Dec/04/2018 at 6:38am
Probably just a stuck lifter. The back firing may have caused it to stick, took a little time to loosen back up. The lifters will collapse over time as the springs weaken with age. I've had them stick in the AMC six when it sat for a long time, like several years, with a good many miles on the engine (80K+). Had to replace 3-4, but at the price I replaced all.

One observation -- did you have that open air filter on the old carb, or the stock air filter assembly? If you had the stock assembly with a heat stove (or even without that) that's your old weather running issue. The closed filter housing even without a heat riser tube (heat stove) will run better than an open filter element sucking in lots of cold air.
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