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AMC 401 engine problem |
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shootist
AMC Addicted Joined: May/24/2012 Location: Triad, NC Status: Offline Points: 1023 |
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Very odd, you have checked the obvious culprits. Since you have the intake off I would check your cam, lifters and lifter bore. Make sure the lifters don't have wobble when they are seated and make sure the bases are not worn.
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304-dude
AMC Addicted Joined: Sep/29/2008 Location: Central Illinoi Status: Offline Points: 9082 |
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Just an odd thought... If you have an old set of timing gears, you can check the keyway clocking to timing marks compared with your timing set. There was some discussion about off timing marks long ago.
I have my set that I pulled with a good running engine. Can post a picture, to give some indication that might be the issue. I had a new set of gears long ago with what looked like a timing mark on the reverse side. Which did install proper, but threw internal engine timing off. |
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71 Javelin SST body
390 69 crank, 70 block & heads NASCAR SB2 rods & pistons 78 Jeep TH400 w/ 2.76 Low 50/50 Ford-AMC Suspension 79 F150 rear & 8.8 axles Ford Racing 3.25 gears & 9" /w Detroit locker |
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Vweberdk
AMC Fan Joined: Apr/25/2017 Location: DK Status: Offline Points: 16 |
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Both cam and lifters are new and look like new exept from the lobe which the paint/Black stuff is worn off. I have tried move the timing 1 and 2 towards advanced,- but compression still the same. Tried with the old cam, lifters and rocker arm, and it kind of got worse...
Hmm i have a friend that will come tomorrow with a degree plate amd a needle gauge. Lets see if he Can do some hokus pokus and make some out of this crazyness |
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SCRAGTOP
AMC Nut Joined: Jul/03/2007 Location: Chesapeake, VA Status: Offline Points: 367 |
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I think your leak down is on the high side... When you re-lapped the valves after my last post, did you do a blue check? There's only so many causes for losing compression... Valves not sealing, valve(s) open (valve train issue or overlap) , rings not sealing, head gasket not sealing.
I read a few posts about rounded off cam lobes. I do not believe that would cause your issue. That would open the valves LESS and start your valve motion slower and end sooner... I read a few posts about timing chain alignment. Keep in mind the alignment marks should be near each other. I rebuilt a Pontiac one time and the alignment marks were supposed to BOTH be at the bottom of the gear in the same vertical plane. Very strange to this old AMC guy. I think you need to stay focused on combustion chamber sealing... |
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shootist
AMC Addicted Joined: May/24/2012 Location: Triad, NC Status: Offline Points: 1023 |
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I would also go back and recheck all of your compression and leak down numbers again. Something is just not right in the information we are seeing. There is an obvious loss of pressure occurring in the cylinder and there are only a few things that can cause that.
bad rings bad pistons bad bore leaking head gaskets valves not sealing (sticking, bad lapping, burnt, etc) cam degree way off and not in synch with the pistons travel invalid testing/test parameters Think that just about sums up all possible causes I can think of. It is pretty simple, piston moves down intake valve opens, air gets drawn in as piston reaches BDC intake and exhaust valves reach fully closed position, piston begins upward compression stroke, close to TDC spark plug goes zap, air/fuel mixture goes boom, piston starts moving back toward BDC, close to BDC exhaust valve starts to open, piston starts back upward and exhaust valve starts to close, back at TDC exhaust valve is fully closed, piston starts moving down, intake valve starts to open........ You get the idea. |
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rondo
AMC Fan Joined: Nov/28/2014 Location: ca Status: Offline Points: 17 |
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At this point, I think you need to look for something simple that is wrong with your set up. make sure your distributer cap is wired correctly-the firing order goes in a clockwise direction and is 18436572 just like a chevy. the EVEN numbered cylinders are on the passenger side of the engine. I have seen engines with the firing order wrong and they ran all crazy...but they ran. try a different distributer if you have one. Use a different timing light if you have one too.
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rondo
AMC Fan Joined: Nov/28/2014 Location: ca Status: Offline Points: 17 |
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OK, time to put away the timing light and go old school... start the car and turn the dist. back and forth slowly-left slowly, right slowly... you will notice it will speed up or slow down, etc.... the point is, you will hear it run better or worse.get it to a point were it speeds up when turned counter clockwise, and slows down when turned clockwise. mess around with the timing in this way and keep in mind that if you turn your dist. past this window, the rotor will actually start arcing to the next post in the firing order (because that post is then closest to the rotor). this will cause it to fire at the wrong time possibly giving the readings you are getting, im not sure. The possibility of this being other than an ignition issue seems slim at this point...
Oh, and put your old dist. back in too, until you get this sorted out. it's just one less variable to consider. Every time you install a new part, you run the risk of getting a bad part, and don't think this doesn't happen. You need to return to as many of your old parts as you still possess. The timing chain is one thing to change back if you can. you already tried your old cam/lifters and it was not fixed...worse maybe is what you said.....it shouldn't have been worse-that is kind of a result-SOMETHING you are messing with is the problem. I'm wondering...Is it possible to install the cam gear 180 out on the camshaft? there IS a little thing that looks like a keyway that ISNT a keyway, but I doubt it could be assembled wrong-but then again I never tried. its something to check anyway Edited by rondo - Apr/26/2017 at 8:42pm |
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Someassemblyrqd
Supporter of TheAMCForum Joined: Jul/02/2012 Location: Renton, wa Status: Offline Points: 458 |
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Morten - when you refreshed your engine, did you pull the piston and replace the rings? If so, is there a possibility that [with the exception of #1 Cylinder] the rings were not staggered, but with the ring gaps aligned, allowing compression blow-by.
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Greg E.
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rondo
AMC Fan Joined: Nov/28/2014 Location: ca Status: Offline Points: 17 |
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I was just wondering the same thing- did you replace the bearings without removing the pistons, or did you dis-assemble the entire engine? I've been assuming you just pulled the pan and did a bearing swap that way.
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Vweberdk
AMC Fan Joined: Apr/25/2017 Location: DK Status: Offline Points: 16 |
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Hi guys.
I guess its time for a little Update, not that there is much new to tell. Its for sure still pretty dead. Vi took the the timeingcover and intake manifold off. Had a degree wheel installed on the crank and a gaugeclock on the intake valve on cyl 1. The timing chain were installed as default, with cyl 1 at TDC and the dot marks alligned faceing eachother. Recording to my cam card, my intake valve should begin oppening approx 1,5 degree before TDC. Well it was nearly as spot on as you can get. So i know for a fact my timing gear and cam are working as they should. Than we tried cranking the engine, and hold our hands over the each intake, and the was alot of sucktion/vaccum. Maybe a little less on cyl. Nr 7 but not much. than we took another compressiontest. Strange thing happened. Now we have approx 5,5 - 6 bar / 80-90 psi on all cylinders. I guess this would be an okay (not what i could wish for) but on a cold engine with a mild cam this would be enough to crank and start the engine. We than reassembly the timingcover, and intake, and took another vaccumtest on the intakemanifold, again on the starter. Again not much vaccum,- around 3-5 in/HG on the starter. We than installed the ignition, distributor, coil a.s.o. Testing that we have fuel, spark and of course free air flow. We know had had some sort of compression. Cranking the engine with fingers crossed, but not even a little fart.. Doublechecked ignition, timing and pulled all spark plugs out. We can see all cylinders get fuel, except cyl 1 and 2 at the front. Thoose two, were not wet of fuel of some reason i dont understand. Than we tried again, but this time with a little help from a spray of "diesel start" - but still nothing. We tried many different positions with the distributor, but nothing would even give us a little indication of an ignition. So this is basic were i am right now.. i ordered a new High torgue starter Yesterday, because the my current one never had turned the engine in the speed i wanted it to, and after using it pretty hard last 3-4 weeks its getting even worse, so my cranking speed is very slow, and after 4-5 sec of cranking, its like its giving up. Battery is New, and since i dont know the age and origin of the poor bastard - i give it go. I also ordered a New distributor gear for my old dist. and im going to try installing the old ignition controller, and maybe buy a New coil. Well i am simply just lost for now.., if the things i Wrote dont seems to do magic, i'll might just buy a bag of marshmallows and make me a great fire... |
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