Low Mileage original 318 suddenly dead on 5 and 7 HELP!

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dodgethis12

dodgethis12

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Hey guys this pertains to my 72 Scamp. 84,*** original miles. Internally untouched since new. Car spends most of its time sitting in the garage. Suddenly it has developed a dead miss on cylinders 5 and 7. Plugs are wet and plugs are good. Have swapped in a second set of plugs, wires, cap, rotor etc. I have fire and I have gas. However removing the wires from the dist. cap while running reveals that there is no change in the miss when 5 and 7 are disconected.

When I pull the other 6 wires there is a definate change in the engine. The miss is dead miss, never clears up, never goes away even at higher RPMs.



Any ideas? Car is very well babied...never raced or romped. Has placed at Carlisle...

Collapsed lifter from sitting? I guess my next step here is to pull a valve cover. Just seems weird as cylinder 5 and 7 are side by side on engine and on the dist. cap..... initially led me to believe it was the ignition.

any help appreciated. Thanks!

PS. I forgot to add.... added seafoam into oil ran engine, drove car, etc. Changed oil to clean oil after.... still nothing.
 
Run a compression test.
 
Put NEW plugs in it, see if it comes back. If not, compression check! Adjacent cylinders could be a head gasket.
 
dodgethis12 said:
Hey guys this pertains to my 72 Scamp. 84,*** original miles. Internally untouched since new. Car spends most of its time sitting in the garage. Suddenly it has developed a dead miss on cylinders 5 and 7. Plugs are wet and plugs are good. Have swapped in a second set of plugs, wires, cap, rotor etc. I have fire and I have gas. However removing the wires from the dist. cap while running reveals that there is no change in the miss when 5 and 7 are disconected.

When I pull the other 6 wires there is a definate change in the engine. The miss is dead miss, never clears up, never goes away even at higher RPMs.



Any ideas? Car is very well babied...never raced or romped. Has placed at Carlisle...

Collapsed lifter from sitting? I guess my next step here is to pull a valve cover. Just seems weird as cylinder 5 and 7 are side by side on engine and on the dist. cap..... initially led me to believe it was the ignition.

any help appreciated. Thanks!

PS. I forgot to add.... added seafoam into oil ran engine, drove car, etc. Changed oil to clean oil after.... still nothing.
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First, Before you pull the valve covers do a compression test on all eight cylinders with all plugs removed. Do a dry test and then squirt some oil in the cylinder and take a second test. Compare the numbers.
 
try switching the wires or double check your firing order, these are sometimes crossed by accident because they are next to each other on the cap
 
pull the valve cover and see how far the pushrods went thru the rockers, gather the pieces of them and install new rockers
 
Easiest thing to do first is a compression check. Does seem odd though. You say the plugs are wet. We are talking gas wet right? If you remove 5 or 7 plug and wire and clamp the plug to ground you see spark correct? If you do then it has to be compression. Only thing. Even a compressed lifter would give you some valve movement I would think. Plus if the valve was not opening where is the gas coming from? Are you getting any steam in the exhaust? I am thinking maybe blown head gasket between 5 and 7. Or worse. How about oil in the coolant or coolant in the oil?
 
Never thought of that. Makes sense. Likely exhaust. Just keeps pumping same dirty air.
 
waggin said:
pull the valve cover and see how far the pushrods went thru the rockers, gather the pieces of them and install new rockers
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What Waggin said.
 
plugs replaced twice now and yes they are gas wet. Firirng order checked multiple times by myself and my father.... as a second set of eyes usually catches a simple brain fart...... Just seems odd that it happened sitting. The car ran fine.....sat for 6 months....start it up and dead miss. It ran fine before it sat for 6 months. Its hard to figure that if blew a head gasket sitting still.

I guess I will compression check it. There is no steam or any tell tale sign in the exhaust other than it smells a little rich.
 
Maybe there is some corrosion on the reluctor. Just thinking out loud.

Also you might want to check the gap it should be .008 checked with a BRASS feeler gauge.

EDIT: Do you have spark to the wires on those cylinders? If so I guess it eluded me in your OP.
 
no oil in coolant or vice versa so if it is a head gasket its between the 2 cylinders...
 
Huh?

Just to check to make sure the valvetrain is not involved. As Waggin offered.

Bank. As in bank of cylinders.

Need to get used to how this forum works. Reply is to 73 Abodee
 
73AbodEE said:
xs2 ???
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I am a compression numbers guy first then the valve cover. If you take the valve cover off then do the compression check you end up with oil everywhere unless you put the valve cover back on. My dear departed friend always told me to work with the KISS program.... Keep It Simple Stupid!!! It has worked well for me.
 
The plugs will be wet as hell cause them two cylinders ain't hittin. Run a compression test.
 
Oklacarcollecto said:
I am a compression numbers guy first then the valve cover. If you take the valve cover off then do the compression check you end up with oil everywhere unless you put the valve cover back on. My dear departed friend always told me to work with the KISS program.... Keep It Simple Stupid!!! It has worked well for me.
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:cheers:
 
Oklacarcollecto said:
I am a compression numbers guy first then the valve cover. If you take the valve cover off then do the compression check you end up with oil everywhere unless you put the valve cover back on. My dear departed friend always told me to work with the KISS program.... Keep It Simple Stupid!!! It has worked well for me.
Click to expand...

in this situation, i would 100% agree with a compression check first, i was just curious if he had taken the cover off, since it only takes 5 minutes.

im kind of a visual inspection guy first. :D i like to see that the valve train is in good working order and there arent any loose pushrods or anything else. i recently went through the whole valve train bs with my 360,:banghead: and now i have my covers set up so that i can take them off and on in 2 minutes flat :cheers: and they dont leak. i also ran the engine with the covers off so i could listen for any noises coming from the valve train and lifters, and didnt loose but maybe 3 drips of oil at 65 psi :cheers:

but yes a compression check here would tell the story
 
73AbodEE said:
in this situation, i would 100% agree with a compression check first, i was just curious if he had taken the cover off, since it only takes 5 minutes.

im kind of a visual inspection guy first. :D i like to see that the valve train is in good working order and there arent any loose pushrods or anything else. i recently went through the whole valve train bs with my 360,:banghead: and now i have my covers set up so that i can take them off and on in 2 minutes flat :cheers: and they dont leak. i also ran the engine with the covers off so i could listen for any noises coming from the valve train and lifters, and didnt loose but maybe 3 drips of oil at 65 psi :cheers:

but yes a compression check here would tell the story
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I am not that fast anymore. More like 30 minutes since my back is jacked.

I can't manage not to get oil splattered all over the place. When I rev the engine to listen for changes it just happens to me.
 
I'd put my money on valves stuck open since it's been sitting.
Personally I'd skip the comp test and pull that valve cover to make sure the valves are closing all the way.
If you have spark and fuel, then ya already know theres no compression.
 
TrailBeast said:
I'd put my money on valves stuck open since it's been sitting.
Personally I'd skip the comp test and pull that valve cover to make sure the valves are closing all the way.
If you have spark and fuel, then ya already know theres no compression.
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I have to disagree here. The push rods could be through the rockers like Waggin said and there would be plenty of compression if it was the exhaust valve rockers that were bad or those push rods bent. A no compresion could be a carbon issue. I have a trick to fix that and never remove anything but the air cleaner. Being sitting I would bet on the carbon not letting the valves close all the way.
 
TrailBeast said:
I'd put my money on valves stuck open since it's been sitting.
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a very good possibility

Oklacarcollecto said:
I am not that fast anymore. More like 30 minutes since my back is jacked. yes, my back doesnt enjoy that like it used too lol

I can't manage not to get oil splattered all over the place. When I rev the engine to listen for changes it just happens to me. i guess i should have mentioned that it was only idling
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