Cylinder has spark but not firing..

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duey_roc

duey_roc

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So ive had this 360 torn apart 3 times now and im going to scream since ill most likely be doing it again. Heres whats going on...

I have a brand new set of J heads on the motor. I had them put new hardened valve seats in, valve grind, and surfacing all sides of the heads. For some reason, nothing happens when i pull #2 and #8 plug wires out. They're giving spark but im not getting any action into the cylinder. Ive tried multiple sets of spark plugs and they all do the same thing.

The bottom end is stock. Original rings and bearings. I haven't gotten around to doing a compression test on it, but im thinking i have bad piston rings. If i have spark, and i know my cylinder heads are good, i can rule those out. The only other thing i can think of is low compression caused by bad piston rings. What does everyone think? angry9:
 
I think you should "get around to" correct diagnosis and stop the guesswork.
 
That's why I'm open to peoples opinions on what they think the problem is. I'm doing a compression check tomorrow. If it's low, that's telling me it's rings. If it's ok, obviously something else and I'll brainstorm at that time
 
Get the compression check done first and we['ll have more to weigh in on. Make sure to do all eight.
 
Compression check 1st....then a leak down test to see where the leak is at...rings or valves..
 
Could be a valve not closing all the way. After a compression check, pull valve covers and check valve train. Do compression test with valve covers off so you can see what's happening.
 
Check the inside of the dizzy cap for cracks and carbon tracing
Could be grounding out inside cap
 
When you are trying to diagnose spark problems DO NOT pull spark plug wires off. GROUND them instead. This is for several reasons

Check cap and plug wires. "Getting shocked" is not a scientific test

You need a spare cap and rotor anyhow. So why not buy a new one?

Use a good spare plug wire and substitute, or move the plug wire to another cylinder and see if the trouble follows

Change the plugs!!!!!

Check compression!!!!

Squirt water mist around intake, carb base

Check valves/ valve adjustment / rocker movement

At the price of Horrid Freight, everybody can afford a leakdown tester, or they are easy to make.

YOU'VE HAD this engine apart THREE TIMES????????????

THINK man, about what you just SAID!!!!!

What did you expect to see in there that you can't "see" with the engine together?

Flat cam

bad compression, either rings or valves

broken valve spring(s)

no ignition

intake/ vacuum leak
 
67dart273 said:
when you are trying to diagnose spark problems do not pull spark plug wires off. Ground them instead. This is for several reasons

check cap and plug wires. "getting shocked" is not a scientific test

you need a spare cap and rotor anyhow. So why not buy a new one?

Use a good spare plug wire and substitute, or move the plug wire to another cylinder and see if the trouble follows

change the plugs!!!!!

Check compression!!!!

Squirt water mist around intake, carb base

check valves/ valve adjustment / rocker movement

at the price of horrid freight, everybody can afford a leakdown tester, or they are easy to make.

You've had this engine apart three times????????????

Think man, about what you just said!!!!!

What did you expect to see in there that you can't "see" with the engine together?

Flat cam

bad compression, either rings or valves

broken valve spring(s)

no ignition

intake/ vacuum leak
Click to expand...

lol
 
Ok so here's my compression test. Cylinders 2, 6, 1, and 3 came out at 130psi. Cylinders 4, 8, 5, and 7 came out at 135psi
 
I had a friend just tell me it can possibly be cam timing. I remember when doing the cam swap, seeing that the distributor gear turns freely while the camshaft is away from the distributor gear.
 
Cam timing won't affect just one or two cylinders, and it won't run at all "180 out"

69Mope is absolutely correct

69MOPE said:
Flat intake lobes will have little affect on compression but will not let air/fuel in.
Click to expand...
 
cudascott said:
Have you checked the pushrods?
Click to expand...
Pushrods are all straight. Ill have to check the lobes on the cam. It is the original cam i know. I did check it briefly when the motor was apart but i didnt really mic it up and stuff. Wat about that distributor gear? what if when i pulled the cam out it rotated just slightly... wouldnt that affect the timing slightly?
 
If you can set the timing with a light, the gear "can point to China" as one member on here loves to point out. IN FACT on any Mopar V8 you can actually close your eyes and "throw" the gear in, and "throw" the distributor in after it. Then bring up no1 ready to fire, stick the no1 plug wire into what ever dist cap hole that the rotor points towards, and run the engine.

Timing WILL NOT affect one or two cylinders
 
okay lets do this the red neck way. to just a vision check pull the valve covers and the spark plugs and roll the motor over with a rachet at the crack, watch and see if all the valves go up and down and about the same amount of travel up and down, yes i said red neck way, if one or two don't then you may have a lobe gone on the cam. then lets go back to the timing and i am not talking plug wires to the cap to cylinders i am talking disrguture to cam, and yes i said red neck way. crack the motor over so the cylinder no.1 is firing, yes you can watch the valves go up and down and the piston come up. now that you have the motor so it should be firng no.1 take the manual and see which way the the rotor should be pointing to fire no. rotate it a few deg forward or back depending on the rotation of the disputer and slide it in make sure that the rotor is pointing to to fire. now i hope that this did not offend any one but have had to do this one the trail so it may not be the most or best way of doing it but may get the same results. like i said the red neck way.
 
rlevs said:
see if all the valves go up and down and about the same amount of travel up and down, .
Click to expand...

The first part of your backyard diagnostics was great.

So far as the second part, This really doesn't prove much. If the cam and ignition timing are correct for no1, "the rest will follow"
 
rlevs said:
okay lets do this the red neck way. to just a vision check pull the valve covers and the spark plugs and roll the motor over with a rachet at the crack, watch and see if all the valves go up and down and about the same amount of travel up and down, yes i said red neck way, if one or two don't then you may have a lobe gone on the cam. then lets go back to the timing and i am not talking plug wires to the cap to cylinders i am talking disrguture to cam, and yes i said red neck way. crack the motor over so the cylinder no.1 is firing, yes you can watch the valves go up and down and the piston come up. now that you have the motor so it should be firng no.1 take the manual and see which way the the rotor should be pointing to fire no. rotate it a few deg forward or back depending on the rotation of the disputer and slide it in make sure that the rotor is pointing to to fire. now i hope that this did not offend any one but have had to do this one the trail so it may not be the most or best way of doing it but may get the same results. like i said the red neck way.
Click to expand...

this^ use the KISS principle...:blob:
 
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