Mysterious problem, please help!

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NorthernSwede

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Hi!

I've got a '66 Dart with a 4barrel carbureted 318, and oldschool igniton, 360 heads and intake. The carb is a Holey 650 vac sec.
It all started with me hearing a ticking noise from the engine and noticing that some of the lifters were done for. So i changed the lifters just to notice that I still had the ticking noice and that the engine besides that doesnt run on cylinder number 5, 6 and 7. So i took out the engine and changed the oilpump and checked all the bearings which were all fine. So now the engine is back in the car with a new oilpump, new sparkplugs, new distributor cap, new lifters, new rotor. The ticking is almost gone altogether, all 8 cylinders have good compression when the engine is running so the valves shut properly. The camshaft is all but new, very good condition. But the engine still doesn't run on 5,6 and 7. I can't figure out the problem, anyone that has any ideas? The sparkplugs give spark on the faulty cylinders, maybe not at the right time? The plugwires is in the right order on the distributor, at least according to what the 360 intake says.

Please, any ideas will help, I'm running out of them myself
 
What shape is the carb in? Sounds like it may need a rebuild. How sure are you if they have spark that they are not firing? What was done with the distributor while the rebuild was happening? Any chance the shaft got bent during the work or pulling/installing?
 
Well the distributor is a strong possibility but as stated above those three cylinders did not fire before removing the engine either. Well, if i remove the plugs and lay them on the exhaust and turn the engine they give a good spark. And the plugs are new, maybe bad plugwires? I have a 650 double pumper that I can try with, what tells you that it might be the carb? Well and how I know that those cylinders are dead, quite simple. I start the engine and pull the plug wires from the sparkplugs one by one untill I find one that doesn't change the way the engine is idling.
 
It's real easy to cross the wires on 5 & 7 but it sounds like you have a vacuum leak. Does the car have power brakes? Maybe the booster leaks.
 
What kind of shape is the timing chain in? There is a metal tab cast into the timing cover that will start hitting the chain and making a ticking sound when the chain gets too much slack in it and needs to be replaced. When that happens, there will be all sorts of weird problems cropping up.
 
The plugs that are NOT fire, how do they look compared to the others?.....wet, dry.....oilly?

Check resistants in the ign wire. compare good wire/firing cyl with non firing cyl

Swap carbs, thats a good idea as well!

vac leak from booster, also worth checking out.
 
Hm, the vacum on the ignition is broken, i just noticed that it leaks air, is that the problem? It shouldn't skip cylinders just because of that? No power brakes whatsoever, I'll check the timing chain. Well, on cyl. nr 7 it looks like the plug has been firing and number 5 is completely dry, I have not checked number 6.
 
You mention good compression when running..??? Have you done a compression check? Sounds more like a head gasket to me...doesn't explain the ticking which could be the timing chain hitting the cover or an exhaust leak which would/could be different after reinstalling the motor. You didn't mention pulling the heads, just replacing the oil pump.

Did you remove valve covers and make sure all the valves are opening and closing? Just because its a new cam doesn't mean it couldn't be wiped out from a bad break-in...
 
Make sure the distributor is not worn out, I have had a problem like that, the rotor was running eccentrically.
 
On dual planes 6 and 7 share a plenum.. So if the carb had an issue you might see issues like that. If the plugs spark when grounded, you have spark. You need fuel, compression, and spark to have it fire. Are you CERTAIN there isnt an issue with compression? What do you get for sylinder pressure readings for all 8?
 
I have done a compression test on all cylinders, not saying that the readings are correct since the meater is quite old but it shows roughly the same on all cylinders, between 90 and 100 Psi. Which seems low but more than half of the cylinders run on it. I think i got those three cylinders firing though by taking apart the distributor and cleaning up ground points and such but still have a very loud knocking sound coming from the engine, specifically at low revs and when throtteling, when holding steady throttle at around 1500 rpm there's no sound. Still runs really rough too, not at all at idle, have to get either the accpump to squirt or hold around 1500rpm for it to stay alive. When trying to let it idle it simply dies. I have the ignition breakerpoints set at 0.4mm, is that to low? Is it possible that it's the timingchain making that loud noice? The lifters have stopped ticking altogheter no when running for a while, thats comforting at least, and yes i have lifted on the valvecovers and all lifter move well.
 
I don't have a reference book handy but IIRC the poits should be around .17mm...
 
Not wanting to idle on it's own and having to pump the acc. pump to keep it running is a clear sign the carb has a problem with fuel delivery and may be your problem. BTW: 90-100 psi is barely enough to fire decent. Sounds like the engine is very tired and needs rebuilt.
 
You have low, but consistent compression, and spark to all cylinders. That only leaves fuel and timing.

Changing lifters alone is not good. Once the cam and lifters break in, their surfaces are mated. Your lobes may be bad even though they look good to the naked eye.

Does the spark in the bad cylinders look exactly the same color as the spark in the good cylinders? Just because you have a spark in the bad cylinders, doesnt mean that it is a good spark. A weak spark can be as bad as no spark at all.

Are you sure all of your intake runners are clear of debris? If the motor was apart for any length of time, there could be a mouse or squirrels nest, or something blocking some of the runners. You would be surprised at the things I have found inside used intakes. One time I found a mouse nest. Another time, an old rag. Someone must have used the rag to cover the intake, then the rag fell in and got wedged into one of the runners over the course of time and movement.

Is the distributor correct for the motor? Is the distributor installed correctly? By that, I mean did you install the distributor using TDC in cylinder #1 on the compression stroke, or did you just put it back in the same way that you took it out?

I once had a car where the distributor was installed several teeth off, then the spark plug wires were arranged to compensate. When I put on a new cap, I did not bother to look at the order of the plug wires because I was going to put them back on in the proper order anyways. When I put the plug wires on in the correct order, it ran like crap. I put the old cap and rotor on, still ran like crap. I tried another distributor, but when I installed it, in order to save time, I installed it exactly in the position that the other one was removed, which just duplicated the problem. Still ran like crap. Took me a while to figure out what had happened.

If you havent already done so, pull your distributor and make sure you put it back according to proper procedures, not how you took it out. Then redo all of your wires in the proper firing order.
 
Well as I said I wouldn't trust the compression meter to show the right value, especially not this time since it has been run like 5000km since new forged pistons. I do sincerely not think that compression is the problem.

The distributor is in the right place, i TDC'd the engine when putting it back.

And regarding the lifters I think they simply got bad from standing still too long since the camshaft and lifters were changed in -02 and the car has barely been driven since. The surfaces of the old lifters were entirely flat and so were the lobes, i checked.

.17mm? That sound really, really small. Sure you don't mean .017 inches?

Well I guess I'll tear the intake again just to check since I really can't find a problem. I'll try with the old carb too, but right now I'm more worried about that knocking sound than the car running bad. I mean it running bad should be something simple like the carb or some nicked intake gasket or something. But the knocking sound, well I dont know, anyone got any suggestions? The sound only occurs when putting load on the engine and is quite a deep sound. More like a hammer is trying to get out of the damn thing...
 
Are you sure the noise is coming from your engine if your flexplate cracks or the bolts rattle loose it can make a ticking/knocking noise like the engine can.
 
Well the flewplate seemed allright when I put the engine back and i tightened the bolts with loctite so they should sit firm
 
Very interesting problem you've got going on Swede. I'm just pulling this out of my arse, but, have you put a timing light on it yet? And if so, was the timing marker erratic? If it was, it might serve you well to replace the distributer bushings, as this would cause erratic timing issues. Also, how are you setting the gap of your points? I've had more accurate dwell adjustment when cranking engine w/dwellmeter, as opposed to "bumping" engine and using feeler gages. Just random thoughts.....
 
You mean that the stroboscope light flashes on diffrent places sometimes? Like -5 sometimes and -15 some times? Actually yes it does. The gap of the points is at the moment set to 0.45millimeters I have tried from .35 to .50

If this is true and the bushings are bad, could this cause that knocking sound?

I really want to pinpoint that sound, I mean if it is something as simple as the timingchain which I'm going to check this week, well then all is good but say its a bad pistonbolt or some other "takeaparttheentireengine" problem then that's really, really bad... I really dont have the time to take the engine out again though I'll have to make time if I have too. I need the car running. I'll try to get a good audio clip of the sound if I can.
 
Sometimes knocks can be tough to find. About 100 miles after I installed my new engine in my Cuda it developed a low knock that was hard to find cause you could barely hear it when stopped and listening to the engine under the hood but when running down the road you could hear it really well. I didn't have a mechanics stethoscope so i cut off a 3' section of old wooden broom handle and put it against various parts of the engine with it running and put my ear to it. The wood transferred sound and I was able to tell the noise was loudest coming from the #8 header tube. I couldn't see where it was hitting anything but after closer inspection I found it was bumping against the engine to trans. bracket. I took the bracket off and ground 1/8" off of it where the header tube hit it and re-installed it and the knock was gone. You might try either getting a stethoscope or using a piece wood broom handle and listen around. Good luck.

BTW: loose dist. bushings can't make it knock.
 
Try to locate a garage with a "Frame Ear" or "Mechanics Ear". You may be able to rent one at one of the car parts places. I know a garage that has one and it is really neat.

Basically, its a bunch of small wireless remote microphones that attach to various points on your car. Each one operates on a different frequency. The mechanic rides as passenger while someone else drives. He cycles through the different microphones until he locates the sound. Then he can stop, reattach all of the mics to the general area, and can actually pinpoint the sound. He told me that it he bought it to located chassis noises, but it works really great for engine noises too.
 
Hm, I just heard a new possibility from a friend, since there's only a electrical fuel pump in the engine compartment he said that it's possible that the noice is coming from where the stock pump sits. Apparently something can come loose there when the stock pump is removed, or atleast that's how I understood it.
 
Some electric pumps can be real noisy but I never heard one knock but I guess if it's mounted loosely it could do most anything. I had one on my car for a while and it sounded like a weed eater running. Drove me crazy so I switched to a mechanical pump.
 
The firing order is 18436572

5,6 and 7 fire consecutively.

5 is the middle one in the firing order. maybe there is an internal short of some kind in the distributor, causing the spark from 5,6,and 7 to short to ground instead of down the plug wires to the plugs.

Look for anything loose inside the distributor, maybe the condensor wire?
 
The fuel pump eccentric could have come loose(causing the noise) but that would not cause it to be dead on cylinders, I would check to make sure the rocker arms are not too tight or that the proper pushrods were used, it's possible it may have sunk valves (burned exhaust seats)could also be a sloppy timing chain(hitting timing chain cover) you can take a long screwdriver and touch it to the engine and put your ear to it(like a dr's stethescope) and narrow down where the noise is coming from....Hope this is helpful.....
 
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