not sure, maybe a blown headgasket

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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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Chances are the head gaskets are blown,....hopefully thats all!....where they steel gaskets, or compositions?....how did you seal them?.......plus check the head dowel heights (put the head bare on the block, with no gasket, to see it if sits flat?), see if there holding the head "off" the motor enough to allow the gasket to blow due to pressure,......before the heads go back on, have them "magged" at a machine shop for cracks, going to cost a few bucks, but better than chasing your tail later, if their cracked now!......been there, done that!

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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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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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