Car not running right

[Mr Lee]

383, 4 speed

Fresh rebuild with about 700 miles. Car just doesnt run right.  Doesn't have the power it should.  I haven't taken it past 4,000 rpm yet because it doesnt even feel like its happy to go that high.  Like instead of getting smoother and stronger as it revs, the engine sounds kinda rough, and the power doesnt keep building, so i shift it. 

I keep fouling plugs.

One of my spark plugs was oily when I checked them so I thought i might be getting oil from under the valley pan gasket into my intake, so I just replaced the intake gasket and valley pan gasket. Plugs still fouling but no longer oily.  Dry and sooty black, but really just two of them which has me confused.  Wouldn't they all read more similarly?  Its #5 and 8 that keep turning black.  See pics. 


Put in new plugs and it drove ok at first but drive it for an hour, the plugs foul and it starts to stall out when coming to a stop. 

Sometimes it hesitates (cuts out very briefly) while cruising on light throttle.  This is a new symptom.


Replaced the coil and voltage regulator.
Replaced my plug wires with some MSD ones and they're all going to the right places.
Air mixture screws are at 1-1/4 turn out. Set with vacuum gauge. (14")
Confirmed power valve is working by turning the mixture screws all the way in - car stalls.
Holley 4160 - was rebuilt by Harms Auto.
Accelerator pump seems to be set right with no play but not pushing down too early.
Vacuum secondaries - i put the lightest spring in the vacuum diaphragm which definitely helped make it run a little stronger, but its still not running smooth. I tested that the diaphragm holds vacuum.

I have the mechanical timing at 18 initial and 34 total, no pinging.  (Checking timing with vacuum disconnected and plugged).  Running the car with vacuum advance on manifold which adds another ten degrees.
Retarding the timing makes it run worse.
I can advance the timing even more but im still not finding that sweet spot where it sounds happy.

Ive verified top dead center with a piston stop and the marks on my balancer.
Mild cam but i dont know the specs.  Was done many years ago. 
Compression test - all cylinders btwn 130-145 psi

Not sure what to do next.  I think its running rich.  I am taking it to the guy who built my engine tmrw.  He is an older guy and used to be a mechanic at the local Dodge dealer back in the 70's. 

Open to suggestions.








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[DeathProofCuda]

You say that the car idles with 14" vacuum.  What is the idle speed at that vacuum?  Is that the highest vacuum reading you can get at idle?  14" seems low for a mild cam.

What jets do you have in the car on the primary side?  Take the front fuel bowl off to verify what you have.  You said the carb was a Holley 4160.  Is it using a metering plate on the secondaries or has it been modified by the addition of a metering block?  Since you had Harms do it, maybe I should assume it is an original correct carb for the car (Holley 4367)?

Looks like you have a mis-matched set of plugs.  Are they all correct for the engine?  Hard to tell from the photo, but it almost looks like the depth of the electrode may be different between a couple of them.

You have a relatively new motor and need to do some tuning of your combo.  Therefore, my first suggestion would be to install a wide-band O2 meter in the car.  It will expedite your tuning process immensely and save you from a lot of guessing.

[Shane Kelley]

Bad fuel. Drain your tank and add some fresh fuel and a new set of plugs. I have been through this same issue myself.

[Mr Lee]

You say that the car idles with 14" vacuum.  What is the idle speed at that vacuum?  Is that the highest vacuum reading you can get at idle?  14" seems low for a mild cam.

What jets do you have in the car on the primary side?  Take the front fuel bowl off to verify what you have.  You said the carb was a Holley 4160.  Is it using a metering plate on the secondaries or has it been modified by the addition of a metering block?  Since you had Harms do it, maybe I should assume it is an original correct carb for the car (Holley 4367)?

Looks like you have a mis-matched set of plugs.  Are they all correct for the engine?  Hard to tell from the photo, but it almost looks like the depth of the electrode may be different between a couple of them.

You have a relatively new motor and need to do some tuning of your combo.  Therefore, my first suggestion would be to install a wide-band O2 meter in the car.  It will expedite your tuning process immensely and save you from a lot of guessing.

It idles around 700
Yeah, 14-15" of vacuum is about all i got.

I dont know what jets are in the carb. Scott said he rebuilds them back to stock.  Do you think i should go w smaller jets?  The engine has been bored .030 over and has a mild cam so I would think, if anything, bigger, but by the looks of the plugs, its already running rich so, I dont know.  I have a lot to learn about carbs. 
Here is a pic of the carb   Its a 4368.  Im not sure how to answer that about the metering plate.  I dont know.

The plugs are different brands because i had to take what i could get but they are all correct for the engine to my knowledge
Champion RJ12YC
Delco R45S

Should i be running different plugs? 




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[Mr Lee]

Bad fuel. Drain your tank and add some fresh fuel and a new set of plugs. I have been through this same issue myself.

Ive been getting gas from different places. And have cleaned and changed the plug. The car not running right has been going on for months.  I wish it were that simple a fix.


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[Shane Kelley]

Bad fuel. Drain your tank and add some fresh fuel and a new set of plugs. I have been through this same issue myself.

Ive been getting gas from different places. And have cleaned and changed the plug. The car not running right has been going on for months.  I wish it were that simple a fix.


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Then it's time for a compression test. Those plugs look black and dry. If if was a rich condition they would look wet. Spark is a possibility but you should check your compression on all cylinders and make sure you don't have a valve hanging open. If you have non adjustable rockers and the heads or block have been cut your pushrods may be a hair long. Compression test will help eliminate that.

[Chryco Psycho]

SO I would start with the basics ,
Start by checking the float levels , after being shipped they can be way off , that can cause flooding for sure . Make sure you have spare seals for the fuel feed line to the rear bowl as they always get pinched unless you are extremely careful !
I wrote a Holley tuning guide in the reference section you can work through step by step .

[Mr Lee]

Bad fuel. Drain your tank and add some fresh fuel and a new set of plugs. I have been through this same issue myself.

Ive been getting gas from different places. And have cleaned and changed the plug. The car not running right has been going on for months.  I wish it were that simple a fix.


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Then it's time for a compression test. Those plugs look black and dry. If if was a rich condition they would look wet. Spark is a possibility but you should check your compression on all cylinders and make sure you don't have a valve hanging open. If you have non adjustable rockers and the heads or block have been cut your pushrods may be a hair long. Compression test will help eliminate that.

I did a compression test yesterday. All 8 cylinders were btwn 130 and 145 psi. 


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[Chryco Psycho]

It looks like cyl 467 are running leaner which are all on one side of the carb , are the mixture screw turned out the same # of turns ?

[DeathProofCuda]

You say that the car idles with 14" vacuum.  What is the idle speed at that vacuum?  Is that the highest vacuum reading you can get at idle?  14" seems low for a mild cam.

What jets do you have in the car on the primary side?  Take the front fuel bowl off to verify what you have.  You said the carb was a Holley 4160.  Is it using a metering plate on the secondaries or has it been modified by the addition of a metering block?  Since you had Harms do it, maybe I should assume it is an original correct carb for the car (Holley 4367)?

Looks like you have a mis-matched set of plugs.  Are they all correct for the engine?  Hard to tell from the photo, but it almost looks like the depth of the electrode may be different between a couple of them.

You have a relatively new motor and need to do some tuning of your combo.  Therefore, my first suggestion would be to install a wide-band O2 meter in the car.  It will expedite your tuning process immensely and save you from a lot of guessing.

It idles around 700
Yeah, 14-15" of vacuum is about all i got.

I dont know what jets are in the carb. Scott said he rebuilds them back to stock.  Do you think i should go w smaller jets?  The engine has been bored .030 over and has a mild cam so I would think, if anything, bigger, but by the looks of the plugs, its already running rich so, I dont know.  I have a lot to learn about carbs. 
Here is a pic of the carb   Its a 4368.  Im not sure how to answer that about the metering plate.  I dont know.

The plugs are different brands because i had to take what i could get but they are all correct for the engine to my knowledge
Champion RJ12YC
Delco R45S

Should i be running different plugs? 




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4368 is the correct carb for a 383 automatic car.  That must be your problem (kidding).  Although maybe someone one here that is a factory carb expert can explain to us what the differences were.

As Chryco Psycho suggested, you should go back and start with the basics to confirm that the carb is set up correctly.  Check float levels, fuel supply pressure, etc.  Get yourself that wide band O2 meter and a good book on tuning Holleys.  As you said, you have a lot to learn about carbs.  This is the perfect opportunity for you to do so.

Your carb uses a metering plate for the secondaries.  You can tell because the back side of the carb does not have a metering block between the carb body and the rear float bowl, like the front does.  See markup of your pic.

[DeathProofCuda]

Keep in mind that just because your plugs look rich does not mean that your carb is running rich at all operating conditions.  Its entirely possible for you to foul your plugs by running rich at idle even though the car is running lean at cruise or wide open throttle.  This is why you want the wide band O2 sensor.  Can you tune without one?  Sure, but it will take much longer and is alot more work.

[JonH]

First thing you need to do is get rid of the AC plugs. Champion cross reference says they cross to rj18yc. Wrong plug heat range will play havoc with your tune/driveability. Other than that along with other suggestions listed previously, you may also have the cam out of time...

[Mr Lee]

Mixture screws are turned out the same on each side, yes.  1-1/4 turns.  Turning them in about 1/4 turn from where they are makes the engine starts to sputter.


The O2 sensor sounds like a plan.  I will look into that.  Thanks.

Correct,  the 4368 is for an automatic, which is what my car used to be. I dont know what the difference is exactly but was told that the difference is negligible. 

Agreed.  I think I should go into the carb and check float levels and jet sizes even though it was rebuilt by a pro.  Never hurts to double check.

I actually had an issue with the float in the front fuel bowl a few weeks ago.  Fuel was coming out of the bowl vent.  I opened it up and the float had fuel in it. I was able to drain it out and solder it up and its been fine as far as I can tell but maybe its time to double check it.

Cam timing...question...    If i confirmed top dead center on compression stroke matches with the mark on my balancer, could the cam timing still be off? 


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[DeathProofCuda]

Mixture screws are turned out the same on each side, yes.  1-1/4 turns.  Turning them in about 1/4 turn from where they are makes the engine starts to sputter.


The O2 sensor sounds like a plan.  I will look into that.  Thanks.

Correct,  the 4368 is for an automatic, which is what my car used to be. I dont know what the difference is exactly but was told that the difference is negligible. 

Agreed.  I think I should go into the carb and check float levels and jet sizes even though it was rebuilt by a pro.  Never hurts to double check.

I actually had an issue with the float in the front fuel bowl a few weeks ago.  Fuel was coming out of the bowl vent.  I opened it up and the float had fuel in it. I was able to drain it out and solder it up and its been fine as far as I can tell but maybe its time to double check it.

Cam timing...question...    If i confirmed top dead center on compression stroke matches with the mark on my balancer, could the cam timing still be off? 


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Yes, your cam timing could still be off even if the mark on your balancer and TDC on the compression stroke match.  Think about it, TDC is determined by the position of your crank, which the balancer is bolted to, and alignment is ensured by a keyway on the crank snout.  Rotation of your cam is linked to the crank by your timing chain, so there is plenty of opportunity to install the cam in a position where your valve timing is not correct relative to the piston position.

You would need a degree wheel and dial indicator, and then you'd have to partially tear the engine down to check the cam timing.  Plus you would need to know the specs of the cam that you have installed in order to verify they are correct.  Do you have a copy of the cam card?  Without it, I think checking the cam timing would be pretty meaningless.  The car has been running "reasonably" well, so you know the cam timing can't be too far off.

For now, I'd stay away from checking the cam alignment and instead focus on the tuning basics previously recommended.  Consider the cam timing issue later if you still haven't solved the issue.

Yes, I would also assume that the difference between the 4367 and 4368 would be pretty minimal.  I was just a bit confused why you were running the 4368.  Makes sense now knowing that your car was originally an automatic.

This is the wideband meter I put in my 70 383 4-speed car a few years back:

https://www.amazon.com/AEM-30-4110-UEGO-Ratio-Gauge/dp/B00N3VGPYS/ref=asc_df_B00N3VGPYS/?tag=hyprod-20&linkCode=df0&hvadid=227534560992&hvpos=&hvnetw=g&hvrand=10119149933823857808&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031245&hvtargid=pla-377903111462&psc=1

Good luck with it and let us know what you find out.

[Chryco Psycho]

OK I will say it , if the engine will not run smooth at any RPM using different circuits in the carb the cam could have wiped out a lobe too or as above the cam could have been installed wrong , I have seen cams 11* off with the timing marks lined up , but I would check a lot of stuff before going into the cam . The carb was probably set correctly before it was shipped but in shipping the adjustments will usually be off so you need to check that & the float could still have a problem & may need to be replaced .