5.9mopar
Member
I been chasing this rough idle on this newly rebuilt 360 Magnum engine. Engine runs good and this shaking and stumble only occurs on idle.
See link for video of idle
See link for video of idle
360 Magnum Rough Idle
- Thread starter 5.9mopar
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Donny DartO
Well-Known Member
What have you done up to this point?
5.9mopar
Member
I have checked for vacuum leaks via a smoke machine and found none. I have replaced spark plug wires, distributor cap and rotor to see if another new set would make a difference but no luck. I did a vacuum test to check for vacuum and I'm getting about 10-12 inch , the gauge seems to be Fluctuating and not steady. Would a bad motor mount cause this shake. They are new but the one on the passenger side seems to move more than the driver side. Also im waiting on a NOS mopar electronic ignition kit , to see of a new distributor and ecu would make it any better. Also would incorrect valve lash adjustment cause this issue? Thanks
Professor Fate
Push the button, Max...
Two things come immeiately to mind.
1.) Crap in the carb's idle circuits.
2.) Since you're running a serpentine drive, that means you're running an electric fuel pump. Depending on how much fuel pressure you're running, you could easily be overpowering the floats and dumping way too much fuel into the engine. Eddy carbs don't like much more than 5-5.5 lbs., Holleys can take a bit more, maybe 6 or so. Are you running a regulator, and if so what is it set at? Incorrect float height can also cause the same thing.
1.) Crap in the carb's idle circuits.
2.) Since you're running a serpentine drive, that means you're running an electric fuel pump. Depending on how much fuel pressure you're running, you could easily be overpowering the floats and dumping way too much fuel into the engine. Eddy carbs don't like much more than 5-5.5 lbs., Holleys can take a bit more, maybe 6 or so. Are you running a regulator, and if so what is it set at? Incorrect float height can also cause the same thing.
Might want to pull the top off that carb and double check the float height. Also, the Edelbrock carbs are finnicky about having the idle set too high by setting the idle screw to high exposing the transition circuits. I usually advance the timing to help set the timing.
Does it smoke? Leaking into the ports underneath? We had one member on here, LA, had a CRACKED intake manifold in one runner
Run a makeshift cylinder load test. Do NOT pull the plug wires loose. Instead, short them. I used to pull up the dist. boots and with a grounding probe in one hand, pull a wire up and out a bit, and stick the probe into the tower. Monitor the changes, cylinder to cylinder, on a tach.
If you can, might be quicker to borrow or beg the loan of a known good carb, just for an idle test
Run a makeshift cylinder load test. Do NOT pull the plug wires loose. Instead, short them. I used to pull up the dist. boots and with a grounding probe in one hand, pull a wire up and out a bit, and stick the probe into the tower. Monitor the changes, cylinder to cylinder, on a tach.
If you can, might be quicker to borrow or beg the loan of a known good carb, just for an idle test
furrystump
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what is the build? Valve train sounds a bit noisy. Motor mount won’t do that.
remytherat
Well-Known Member
What cam do you have? This is correct only for a pretty radical cam. For a stock cam this is very low. Suggests late timing and throttle blades open too much.
remytherat
Well-Known Member
That’s just the magnum noise.
You have 1 or more valves not sealing well .
At least according to your vacuum gauge .
Tommy
At least according to your vacuum gauge .
Tommy
Firing order correct?
Donny DartO
Well-Known Member
Did you know you can put 2 inch sections of rubber hose between the distributor and plug wires, then touch a grounded test light to each one and it will kill the cylinder? I just found that out a couple years back, though it was kinda neat.
TT5.9mag
Two atmospheres are better than one
Not my magnum.
5.9mopar
Member
prior to installing the carb, I went thru it because gas was not going in thru the seat needle , I opened it up and ran carb cleaner thru it, for the pressure i am running a regulator with pressure under 6 . I will probably go thru the carb again jut to make sure the float height and all that is good , thanks
5.9mopar
Member
Thanks, thats what I will doing to make sure the float is good
5.9mopar
Member
no i haven’t noticed any smoke, i will try and do that as well, thanks
5.9mopar
Member
I have a oregon cam regrind #1990, if the cam degree was incorrect would it cause that issue im having
5.9mopar
Member
Thanks
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Lifter noise?
If you have a timing light that has a built-in tachometer, like a dial back style..
Set your idle screws so that they are exactly the same as each other and open just enough to bring the RPMs to the highest reading. Once you go past into the two Rich Zone you will see that the RPMs no longer rise and will actually start to go back down. So do that and set them to the highest RPM you see on your tachometer or timing light then see how it idles. Don't forget to lower the idle speed screw on the throttle lever to the desired 750 or 800 RPM on speed and feel free to readjust those idle screws after that has done before
5.9mopar
Member
Not sure of the compression,
Camshaft is a hydraulic cam regrind from oregon cam #1990
Rockers are 1.60 Ratio, 3/8" Stud
Edelbrock performer RPM heads
Edelbrock performer RPM airgap intake
Edelbrock avs2 650cfm carb
I did have a hard time degreeing the cam but I think i got it right, would a incorrect cam degree cause this issue?
Im in southern ca, riverside county
Thanks for your help
MOPAROFFICIAL
If it has tits, it's a liabilititty.
Ill be in highland this week, if you want I can come by and help you.
5.9mopar
Member
Ill Pm you
TT5.9mag
Two atmospheres are better than one
Ha! I’m in Norco. You’re not far. If you’d like me to come have a look PM me.
Yea if the cam didn’t degree in correctly you could cause some shake. But it’d have to be pretty far off. What did you degree it to?
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