Spark issue help

[notadart]

Ah, that's because I don't know what I'm talking about.
I have the metering block off, and am about to remove the idle screws to air-compressor them out. Is there anything else I need to remove from the m block before I do this.

 

[AJ/FormS]

Unscrew everything on the block.Pull out the seals around the mixture screws so you don't lose 'em.Sometimes/often they come out with the screws.

 

[nm9stheham]

Backfires have been known to rupture these power valves. But that 'ought' to effect both sides of the carb.

Is the gunk in the PV area gooey? If so, it could well be ethanol that settled out when the carb was setting. But it would have to set for some months at some point to do that.

Is there a good filter in the fuel line?

 

[notadart]

Backfires have been known to rupture these power valves. But that 'ought' to effect both sides of the carb.

Is the gunk in the PV area gooey? If so, it could well be ethanol that settled out when the carb was setting. But it would have to set for some months at some point to do that.

Is there a good filter in the fuel line?

Power valve looked corroded, but everything was dry.
Only weird thing was 2 gaskets under the power valve.

Nothing black came out when I shot compressed air through. Now the carb is back together, so I guess I'll check it tomorrow.

Fuel filter will be changed. Looked clean, but the fuel that came out of the carb wasn't particularly clean.

 

[AJ/FormS]

well
my opinion is
if nothing came out,then nothing is fixed.
guess we'll see

 

[teringer]

what was the ticking noise did you find it?

 

[notadart]

what was the ticking noise did you find it?

I'm going with successive backfires.

 

[notadart]

well
my opinion is
if nothing came out,then nothing is fixed.
guess we'll see

Yeah, thats my opinion too. Nothing worse than hoping to find something broken and coming up empty-handed. :???:

Gonna grab a new power valve tomorrow, and see if they have a new metering block. If it's not going to be too spendy I might just throw money at the problem.

If that hasn't fixed the issue, I'll toss the spare carb on, then vacuum test the system.

 

[notadart]

Okay! Here we are again. Still stumped.

Carb is sparkly clean and back on. Pretty happy with the setup though my power valve might be a bit low. Meh.

With everything back together I started ******* with my timing more. Run it everywhere from 6 degreed retarded to 10+ degrees advanced. Runs about the same. Still pops when I give it throttle and backfires, and she still smokes.

All plugs show signs of firing now.

THE BIG ONE:
Vacuum test shows bad ignition. (Bounces between 17 and 19 in time with the engine (which has a definite lump to it))

 

[AJ/FormS]

Try the spare carb....................

The bouncing needle, says nothing about the ignition. What it says is; there is a pressure spike back into the intake. If you have just one or two spikes in every eight and they are regularly spaced, it speaks to a faulty intakevalve seal.And that leads to a leakdown test. But if there are a number of high readings with one or two low, that speaks to a vacuum leak at the port.And if its sucking from the bottom of the intake that leads to smoking.The test for this is to put a vacuum gauge on the dipstick tube, and remove the pcv out of the valve cover, and seal the valvecover breather ports. A vacuum in the crankcase on an idling engine proves it.
Burned exhaust valves, or non-sealing exhaust valves, will pop in the exhaust for sure. If you are running log manifolds this can be proven by covering the tailpipe with your hand;not sufficient to seal the opening.(if you have a crossover you will have to seal the other pipe.) If you feel the engine occasionally suck your hand onto the pipe, there is your proof.And time for a leakdown to see which one is doing it.But really, it doesn't matter cuz the only cure is a valvejob.Headers make this test a little harder to prove.Heres the thing tho; if an exhaust valve goes bad, then when that cylinder is on the intake stroke, at idle, the piston will pull air from the header instead of from the carb cuz it is just so much easier. Of course this air has no fuel in it. So that cylinder goes lean. There is also a good chance that the hot exhaust will ignite the mixture in the intake, which it has access to via the still open intake valve. Then you get a pop in the intake which can blow up through the butterflies and further up set things. As you open the throttles the spike moves out of the manifold and into the filter house, creating more popping and havoc.
But, a malfunctioning low-speed circuit will also pop, hence "try the spare carb". Or you can just jump ahead and go straight to the leakdown test. If the leakdown test proves the valves are sealing, then you only have two possibilities; Bad idle circuit, or a non sealing intake port.
Well there is one more possibility, cracked plug insulators, but you said the plugs are new.
Again, trying the spare carb, will rule out the bad idle circuit, at least.
If your car was in my shop, I would immediately go to the LD test.

 

[notadart]

Try the spare carb....................

The bouncing needle, says nothing about the ignition. What it says is; there is a pressure spike back into the intake. If you have just one or two spikes in every eight and they are regularly spaced, it speaks to a faulty intakevalve seal.And that leads to a leakdown test. But if there are a number of high readings with one or two low, that speaks to a vacuum leak at the port.And if its sucking from the bottom of the intake that leads to smoking.The test for this is to put a vacuum gauge on the dipstick tube, and remove the pcv out of the valve cover, and seal the valvecover breather ports. A vacuum in the crankcase on an idling engine proves it.
Burned exhaust valves, or non-sealing exhaust valves, will pop in the exhaust for sure. If you are running log manifolds this can be proven by covering the tailpipe with your hand;not sufficient to seal the opening.(if you have a crossover you will have to seal the other pipe.) If you feel the engine occasionally suck your hand onto the pipe, there is your proof.And time for a leakdown to see which one is doing it.But really, it doesn't matter cuz the only cure is a valvejob.Headers make this test a little harder to prove.Heres the thing tho; if an exhaust valve goes bad, then when that cylinder is on the intake stroke, at idle, the piston will pull air from the header instead of from the carb cuz it is just so much easier. Of course this air has no fuel in it. So that cylinder goes lean. There is also a good chance that the hot exhaust will ignite the mixture in the intake, which it has access to via the still open intake valve. Then you get a pop in the intake which can blow up through the butterflies and further up set things. As you open the throttles the spike moves out of the manifold and into the filter house, creating more popping and havoc.
But, a malfunctioning low-speed circuit will also pop, hence "try the spare carb". Or you can just jump ahead and go straight to the leakdown test. If the leakdown test proves the valves are sealing, then you only have two possibilities; Bad idle circuit, or a non sealing intake port.
Well there is one more possibility, cracked plug insulators, but you said the plugs are new.
Again, trying the spare carb, will rule out the bad idle circuit, at least.
If your car was in my shop, I would immediately go to the LD test.

Thanks for all the advice man. From what I read ( this article: http://www.gregsengine.com/using-a-vacuum-gauge.html ) a jump of 1-2 inches indicates an ignition problem. That's where I got that info.

-I will test for the intake sucking issue (dipstick test)
-I've got headers, so I'm guessing the tailpipe vacuum test will be hard to execute. I'll give it a shot anyway.
-I'm having a little trouble understanding "As you open the throttles the spike moves out of the manifold and into the filter house, creating more popping and havoc." If you could provide a bit more detail that would help me out.

-Plugs are (once again) brand new. Tossed new ones on 2 days ago before the latest round of vacuum testing.

 

[AJ/FormS]

-I'm having a little trouble understanding "As you open the throttles the spike moves out of the manifold and into the filter house, creating more popping and havoc." If you could provide a bit more detail that would help me out.

No problem;I'll do what I can.
--The pressure spike in question is when the pressure momentarily drops on the guage as compression pressure blows past an open intake valve,and enters into the intake,and the pressure there-in rises . The gauge reads it as less vacuum, so the vacuum drops.
--This is the same reason big cams idle at low manifold vacuum; the pistons are ALL continuously blowing some pressure back into the intake.
--This is all fine and dandy as long as the pressure stays in the intake, and as long as the intakes all eventually close before the fire gets lit. If an intake is still open when the spark ignites the charge, then, the fire travels into the intake and lights anything in there, and that is the pop you hear.
--Now, if you are stepping on the gas, and the butterflies are open, then this hot expanding gas can leave the intake and travel backwards through the carb and into the air filter house. Since the carb venturies don't care which way the air is traveling through them, they can dump some gas into that wrong-way airflow. This same airflow is at a higher pressure than atmosphere, so momentarily the low-speed circuit quits.As you open the throttle a little further, following pistons begin to suck(sic) this hot expanding gas out of the plenum and a point is reached where equilibrium may be restored. However this hot burned gas is now inert as it enters a next-firing cylinder, diluting it's charge, possibly pre-igniting it, so now you have a second popping cylinder.This is havoc. As the rpm rises, all this havoc may diminish because there is no longer enough time for that initial pulse to get far enough up the runner. In fact if you burn an intake at 3000rpm, traveling down the highway, you might not even notice it until you slow down for a stopsign.
--Now let's talk about why the intake might not be closing. There are at least three reasons that I can think of; #1) it's burned, and #2) it is lashed too tight, and #3) it has a mechanical problem, such as it's bent, or there is a guide problem or there is a hydraulic lifter problem or a spring problem.
--The LD test will determine if there is a valve problem, and which one is the trouble maker. Then you have to figure out the why of it.

 

[notadart]

Still haven't managed to do a leakdown test (compressor fitting issue)
Discovered this after warming up my engine, of course.

Once I pulled all the plugs, I noticed that all but one are now running rich. (see the pic)

Any further advice? I'm gonna start the leakdown test on that cylinder, and fab up a new spark wire for that plug, see if that's the issue.

 

[InItSwingIt]

I don't know squat comparatively. but I'm curious as to how "good" it ran with the new cam. Seems like more than one factor causing problems with the carb and vac issues; I might reconsider the assumption it ran fine after the cam swap, retrace what was touched and assume the original equipment to be the only "knows state".

 

[MoparLeo]

JMO but I recommend that you use the proper Champion spark plug that was designed for this engine. I have found over the years that the ignition systems work better when you use the OE parts. All Chrysler products used Champion spark plugs, just like Fords like Auto-lites, Gm's like AC's ( Which happens to be the initials of Albert Champion ) and so on. And you don't have to make a new plug wire to check to see if a wire is bad. Just swap the plug wire from another cylinder and see if the problem follows the wire.
Oh, and if you didn't know before, Holleys make good power but are not street reliable. Constant problems with the metering block getting dirt in it. Use top quality fuel filters and use one between the fuel tank and fuel pump and between the fuel pump and the carb.
I run a Thermo-quad on one Challenger and an Edelbrock AVS replacement carb on the other one. Easy to adjust and no fuel problems like leaks etc... Like I said JMO.

 

[67Dart273]

JMO but I recommend that you use the proper Champion spark plug that was designed for this engine. I have found over the years that the ignition systems work better when you use the OE parts. .

Sorry my friend but this is absolute nonsense. There are better'n 'n wors'n parts, components and plugs, but OEM is not necessarily always better.......Certainly true of plugs

The OP

What did you do for timing?

Have you checked that TDC is actually correct? (Piston stop)

Have you checked that the advance (mechanical) is actually working

I think you mentioned "all the way retarded to 10* advanced" TEN DEGREES is not very much advance on a performance engine, especially if the mechanism happens to be stuck

 

[mguner]

The way that looks it sat on its side with ethanol blend in it for a while. Definitely need to make sure the passages in the metering and idle circuits are completely clean and functioning. May want to borrow a known good carb.....

 

[notadart]

Sorry my friend but this is absolute nonsense. There are better'n 'n wors'n parts, components and plugs, but OEM is not necessarily always better.......Certainly true of plugs

The OP

What did you do for timing?

Have you checked that TDC is actually correct? (Piston stop)

Have you checked that the advance (mechanical) is actually working

I think you mentioned "all the way retarded to 10* advanced" TEN DEGREES is not very much advance on a performance engine, especially if the mechanism happens to be stuck

Tried a variety of timings, didn't seem to run any better. (35+ degrees total)
Haven't checked if my mechanical advance is stuck.
I should investigate TDC more carefully now, it's been a lot of ******* around since the last time.



and Mgunner, just cleaned the carb out very carefully, but I'll toss on my old eddy to check, I guess. Kinda sucks to have to swap fuel lines too, bah.

 

[KitCarlson]

Haven't checked if my mechanical advance is stuck.

So, pop the distributor cap, twist the rotor, estimate or measure, how much it turns, an how well it returns. That only takes a couple seconds. Crank degrees is 2x distributor degrees. Twist in direction the distributor normal turns.

 

[nm9stheham]

Once I pulled all the plugs, I noticed that all but one are now running rich.

Any further advice? I'm gonna start the leakdown test on that cylinder, and fab up a new spark wire for that plug, see if that's the issue.

If that plug was not firing, then you would have a flat miss all the time. And you would smell gas very strongly on that plug. If you are going to test leak down or compression on one, test them all.

Ideas:
- Are plug PN's all the same? Are the lengths of the plugs' insulators the same? Just looking for that #2 plug to be a different heat range than the others; perhaps mismarked, but the insulator difference would tell the story. (That seems unlikely since you did indeed change plugs....)
- Pull the valve covers and check the lift on intake and exhaust on all 8 cylinders. There will be some variation if the lifters leak down any, so this is best done right after the engine has been idled for a few minutes to pump them up. See if the lift is low on #2.
- Use an ohmmeter to check the end-to-end resistance on all the plugs wires. Does not matter if they are only 6 months old....
- Pull each plugs wire one at a time (with the car not running) and put into a spark tester, restart, and see if each plug's sparks are about equal.
- Maybe the best idea: If there is nothing different in the #2 compression, or lift, or spark, then #2 has a bad intake gasket leak; on one corner would be a good spot for that to happen. It would be lean and the rest relatively rich. That would explain a lot; too lean, and the mixture will not fire in the cylinder, but will go down the exhaust and be lit off in the hot exhaust when opened up at all. R&R of the intake is not THAT much of a hassle

 

[notadart]

Finally got to the bottom of the issue.

3 busted lifters.

I don't know whether the ones I put in had just been sitting too long, or were mis-machined or what, but they were totally pooched when I pulled them out. Got a new oil pump and gauge in case, and they were definitely getting oil.

Anyway, new lifters and rods and she runs a treat! Now it's time to get tuning again!

Thanks everyone for all the help!

 

[67Dart273]

I would not assume the lifters "just went bad" There is a reason. Lifters are very reliable. Three? I'd be more than suspicious. Post photos of the failed pieces

 

[notadart]

I would not assume the lifters "just went bad" There is a reason. Lifters are very reliable. Three? I'd be more than suspicious. Post photos of the failed pieces

Oh yeah, I'm aware of the suspicious circumstances, but I can't think of anything else that would cause it. Break in was done properly, oil pressure was good, there was enough oil... I guess we'll just wait and see if it is actually fixed. (Seems great now!)