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I took my 340 Dart out for a real test drive



I did not re-touque the heads soon after I got it started. I have been told I should have done that after the initial startup.

with this information, are these symptoms of a blown headgasket or could it be something else.

thanks again guys.

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A little history on the rebuild.?? What was done.

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A mechanic friend of mine and I assembled the motor in his garage about 6 years ago and it sat in a bag in my garage until this year. I was the one who was responsible for torqing the heads .
so...
I have a couple of questions.
I orginally used an engine gasket set from Fel-pro when we put it together.
What is a better head gasket to use now?
When we assembled the motor I told him I really wanted the motor to be more dependable and idle smoothly than a ground pounder.
He convinced me that a P4452759 cam would be just fine.
While the car was running, it's idle was anything but smooth.
Now would be the time to slip it out and replace it with the P4452782 which I understand is the stock replacement cam for a 1970 340 isn't it.
there is also the P4452757, which is one "notch" up from the stock unit.
What is your opinion of these three camshafts. what would I sacrifice?
thanks

Mike

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That isn't really a very big cam. Very little difference to the OEM 340 type grind. I think that you had better do some checking to see what is wrong. Yes, it sounds suspicious to a head gasket but not nessessarly, they are not that notorious for going out if the surfaces are prepped and torqued correctly. Very few are retorqued.
Pull your valve covers and make sure that all the rockers & push rods are in place. Also check your coolant level in the radiator.

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If there is anything different between them you will see it. oil coating - wet?

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We cannot see the smoke you saw. it could be nothing but condensation 'smoke'. In cool high humidity weather it can get real heavy and drip water from the tail pipe. Oil smoke doesn't have to be a dark blue color either.
Like I said before I am not at this point convinced that you have a head gasket out.

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Can you borrow a compression tester. wire the choke/throttle wide open,take the plug off of the ECU, the plugs are already out, you're almost there. You'll have an answer pretty quickly.

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the ECU is the electronic control module & removing it's electrical plug in eliminates any possibility of an "open" frying any electronic components during our testing. consistant readings pretty much are we are wanting to have & they will vary from ~120-170 psi roughly depending on the CR & the cam & you would want them to be the same within maybe ~10% or so & I am not positive on that % figure. But do post the readings. We are hoping to NOT have 2 adjacent cyls that are WAY lower than the others which would indicate a blown head gasket between the two offending cyls. I would get one that screws in to the cyl with a detachable hose rather than cheap one with a rubber tip that you have to hold to the plug hole while someone cranks the eng & they are not expensive.

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it's 14 MM & most if not all are that size & a few have 18MM adapters(which you wont need). I would suggest you get a fairly good one at your parts house that will continue to give accurate readings years to come. Compression testing is somewhat basic & people have gotten away from them somewhat but they have saved me lots of times when my mind wanted to get away from the K.I.S.S. principle.

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But then the question arises, what caused it to happen in the first place.

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Not having the throttle wired open will affect the readings some, but not so much so that the readings are not valid--your readings are all in the same ball park. Probably not a head gasket.

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#1 140 #2 150 #3 135 #4 135 #5 140 #6 147
#7 145 #8 140

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Could I have run the motor too lean or rich and possibly burned a valve?
Would that cause the over heating and high oil pressure? Would I able to tell anything from cranking the motor with the valve covers off?
but the nagging question is why would it run fine and all of a sudden run poorly?

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would something as simple as fouled plugs be the culprit for the stumbling in the motor...but that doesn't explain the running hot does it.

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take a picture of the smoke cloud????

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If you have the ralley dash, your fuel gauge could be the cause of your gauges reading too high, as the voltage limiter is part of the fuel gauge, and could cause the gauges to read too high or to low if it malfunctions. Happened to my 340 duster, all three gauges, (temp, oil press and fuel level started reading half of what they should have because of the fuel gauge. I imagine a non ralley cluster may do the same if plug-in style voltage limiter freaks out. Head gasket re-torqing is seldom done, so if the bolts were torqued to correct specs, it should not cause a problem.

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that crossed my mind too that the gauges were pegging especially when you said the oil psi was pegged but then I thought nah that couldn't be it because there's all the physical symptoms, the white smoke, the leak at the front of the head & especially the missing and wouldn't hardly stay running. I am going to go out on a limb & say ECU/slight intake&coolant leak/bad voltage limiter as he mentioned.

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Is there a way to test the Breakerless ignition I put in? If there is a vacuum leak and I spray the area w/ starter fluid, will it bubble like a hole in a tire does?

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A parts house can test an ECU but if it doesn't act up when they test it then we are not going to have a valid test but I would have them test it(our run of(bad) luck has to change ). I for sure hate throwing parts at a car expecially after my contributions. Do you have another vehicle that you could borrow the ECU from. An intake sucks the fluid in as opposed to a tire that bubbles it outward & if any fluid is sucked in through a pinhole leak it changes the idle because you are improperly adding extra fuel & drastically changing the mixture & the idle speed/quality will change & I'm thinking that if this was just condensation & if the ECU is the culprit that there might not be any intake issue so I would start there with the ECU. EDIT & white smoke that is what we call steam so you're good there.

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Is there a way to test the Breakerless ignition I put in? If there is a vacuum leak and I spray the area w/ starter fluid, will it bubble like a hole in a tire does?

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A parts house can test an ECU but if it doesn't act up when they test it then we are not going to have a valid test but I would have them test it(our run of(bad) luck has to change ). I for sure hate throwing parts at a car expecially after my contributions. Do you have another vehicle that you could borrow the ECU from. An intake sucks the fluid in as opposed to a tire that bubbles it outward & if any fluid is sucked in through a pinhole leak it changes the idle because you are improperly adding extra fuel & drastically changing the mixture & the idle speed/quality will change & I'm thinking that if this was just condensation & if the ECU is the culprit that there might not be any intake issue so I would start there with the ECU. EDIT & white smoke that is what we call steam so you're good there.

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to review,
The ECU is the orange component that came with the distributor kit when I replaced the dual point. I bolted it to the drivers side fender. It has the large triangle shape plug. Is this is the unit we're questioning?

I have a wiring harness I pulled out of my mothers' (rest her soul) 74 Plymouth /6 Valiant. I think the ECU is still attached to the tangle of wires.

Other than the body panels, every system on this car has been replaced, refurbished or repaired. I'm learning that even though you replace items refurbished by professionals(carburator, dash, alternator, starter, wiper motor) or new (wiring harnesses from YO)...it is certainly no gaurantee that they will work.

Thanks for hanging in there with me.

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Is this is the unit we're questioning?
Thanks for hanging in there with me.

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(1) yes (2) we cant quit now ,we're in too deep

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Did you make sure that the ECU is grounded to good clean metal and not screwed down to painted metal.
Check your oil pressure with a good mechanical gauge.
Yes a misfiring engine can run hot.
You said you fired it up again in one of your later posts - How did it run?
What are you running for rocker arms? If adjustable how did you adjust them? Just a thought but if adjustable they could be adjusted too tight and when the lifter pumps up they are holding the valves open. [/quote




When it bolted the ECU to the fender I DID NOT scrape the paint to expose bare metal. I bolted it directly to the fender, right on top of the paint.

In answer to the question about when I fired it up to warm the motor to check the compression, if I set the idle screw @ around 1500 - 2000 rpms, initially, when still cold, it runs without problems. Very fast but no stumbling.

As it warms up, the engine begins to stumble. If I turn the idle screw back to the 1200 rpms (idle recommended by the cam shaft people) it bounces from smooth to erratic back to smooth.
If I leave it @ 1200 rpms, after a few minutes, it rocks back and forth struggling to run, the light in the cabin flickers, the gauge needles (temp, tach, oil, and amp)shutter slightly in an erratic motion and the motor simply dies out.

If I turn the rpms back up to 2000 before it dies, it will run but stumble.
AT high rpms, the gauge needles return to a calm posture until it stumbles at which time they flinch.

If the ECU is improperly grounded, as I'm now sure it is since I bolted it on w/o prepping the mounting surface correctly, that poor grounding could interrupt the signal, thus resulting in the erractic idle.

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Ground your ECU. It won't hurt. Check to make sure that your carburator isn't flooding over. Look down the carb throat while it is running and make sure that it is isn't flowing fuel. Sounds to me now like it is loading up.

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If it is flooding out the float could be set too high or there could be something holding the needle partially open to allow too much fuel into the bowl. When you look down the throat you should not see any fuel dripping. does it smell rich. If it is dripping fuel it should smell rich and the plugs should be black, which you say they are not so possibly scratch that idea.
On the other hand like Robert said you have the possibility of a vacume leak. OR have you adjusted the idle mixture screws or just adjusted the idle speed. Poor idle mixture can also give the symptoms you describe. A lot like slowly running out of fuel. We are all just guessing here without being able to see the problem.

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First place to look is for are tight clean battery cable connections. Make sure that the battery is fully charged. A marginal; battery will/can make your engine run ratty too, do you have your engine grounded to the fire wall of the car. The engine must be grounded to the body have seen lack of grounds do mysterious things.
As for your key switch returning Spray some spray like spray silicone lube on the key and then put it into the switch and turn back and forth.

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Sounds like a corroded or lose bulk head connection to me.Jumping it at the starter relay bypasses all that.

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Is this what all you guys go thru when you get one of these old cars going after 20+ years?

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either will work on the key. Would like to see a good ground from a head or rear of engine to the fire wall. Should have had one in original state.

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Is this what all you guys go thru when you get one of these old cars going after 20+ years?

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before we had Moparts it was worse

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Make sure that the connections are clean and tight at the bulkhead connector. Recheck your battery terminals and connections. Just because the battery is new it doesn't mean it can't be bad or that the connections are good. did you scrape the factory protectant off the posts? did you scrape the cable ends clean and shiny before you put them on?ake sure that the cable were indeed tight on the posts and that you couldn't grab them with your hands and turn them? If they are not tight or the posts clam together tight without being real tight on the posts you can re pair this by taking the bolt out and clamping the the cable camp together with a vice or vice grips and running a hack saw through the split and then putting the bolt back in and it will tighten down tighter. Rechecking - starting at the battery is the first place I would look and work from there. Making sure all grounds are tight and clean and all connections tight.

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I am going to dive in here and throw out something simple. I had a 73 Duster. Similar issue. Drive fine then for no reason the thing would start missing and everything would go nuts. What i found on this car was at the wire connector coming out of the steering column two of the wires inside the connector had fused together slightly. When hot they made contact and even when moved or if I hit a bump. I bypassed the connector on the two wires and solved the problem. Later I also found this had damaged the switch itself and I ended up replacing it and the connector.

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Just curious.

Is this what all you guys go thru when you get one of these old cars going after 20+ years?

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either will work on the key. Would like to see a good ground from a head or rear of engine to the fire wall. Should have had one in original state.

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