Spark plug read out

Hi fellow Mopar fans,

I have done some work on my 440 engine over the winter and all is just back together and i have been doing some test driving.
I am busy with setting up the carb and ignition for a happy medium, today i decided after done some miles to check the spark plugs.
The electrode and ground strap are clean and grey/light brown, only the base is a bit black from deposits.
The ground strap discoloration seems near the base, to me indicating too much timing right?
There is a very small line near the tip of the ground strap which should indicate a reasonable idle timing according me.
Any tips/suggestions from anyone how this spark plug looks?

Edit: Worth nothing the spark plugs are NGK XR5.

Insulator should be all tan.

This is just my opinion. Seems to me you have it running right now. Some more miles and they will clean up on their own, or you can clean, re-gap, and reinstall, then relax and enjoy the car. If you are still not satisfied, replace the plugs and enjoy as I said above. If you go looking for trouble you can always find something. A lot of us here are so **** about our cars that we see things that may or may not be there. I am inclined to do the same, I guess it's contagious.

Thx for the reply's gents.
These spark plugs come new with a gap of 0.375".
Some say, that with an high output ignition system like the MSD you can increase the gap to create a stronger spark (more heat) as the ignition system can handle the extra load.
Would there be any benefit over running with a little more gap? Say 0.450"?

Currently i still have not hooked up the V-can yet, i have around 15-16* initial advance and 18* mechanical advance.
Hooking up the V-can puts the initial timing straight to 30* when attached on manifold vacuum.
The V-can came with the MSD RTR distributor and is not adjustable.
At the Ported manifold it pulls only a few degrees advance in idle, i only tested it while adjusting and have not driven with it yet but will try soon.

.40 is what I ran without any issues.
Gap changes timing.

odcics2 said:

Gap changes timing.

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Is it? How does that work? Never heard of that.
I can imagen the timing retards as it will take longer for the ionizing process between the contact points...?

Yup, bigger gap takes longer for the spark to jump.
At high rpm, you may see a difference.

So would i improve something by increasing the gap from 0.0375" to 0.040"?

I tend to agree with you. You may have too much timing, or too fast of an advance curve. The black spots might indicate detonation. I'm still trying to learn how to read spark plugs so it's very possible I am wrong.

You haven't mentioned what the engine is internally. Cam, compression, heads, type ignition, etc. I always start with the FSM and work from there when tuning. Gap on plugs was 35 in the day and it still works for me.

The pics don't show super good on my phone, but from what I see, those plugs are too cold. Yes too much timing. Idle is rich, and it could be shadowing playing tricks on my eyes but it looks pig rich towards the mid range. Cut the threads off so you can get a good clear view of the insulator all the way to the bottom. You're doing it right, keep tuning and keep checking!

Jerry Hall said:

You haven't mentioned what the engine is internally. Cam, compression, heads, type ignition, etc. I always start with the FSM and work from there when tuning. Gap on plugs was 35 in the day and it still works for me.

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I did not indeed, cam is a Hughes Engines HE3844BL, 238/244 @ .050"(283/291 @ .008", 108 LSA, 10.5 comp. with 906 heads and MSD RTR distributor.
Plugs are heat range NGK #5, previously i was having #6, should i run #4?

Guess the gap of .0375" is ok then, i will leave it as is.

beanhead said:

Idle is rich, and it could be shadowing playing tricks on my eyes but it looks pig rich towards the mid range.

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I have the idle a bit rich due to the camshaft probably is mixing exhaust gasses due to duration/overlap.
Mid range is doing about 12.5 AFR average on the O2 sensor.

Every now and then, a vintage Champion Spark Plug reading chart will show up on ebay.

A good investment for the tuner!! It'll clear up the questions you have, rather than guessing.

Wietse said:

I did not indeed, cam is a Hughes Engines HE3844BL, 238/244 @ .050"(283/291 @ .008", 108 LSA, 10.5 comp. with 906 heads and MSD RTR distributor.
Plugs are heat range NGK #5, previously i was having #6, should i run #4?

Guess the gap of .0375" is ok then, i will leave it as is.



I have the idle a bit rich due to the camshaft probably is mixing exhaust gasses due to duration/overlap.
Mid range is doing about 12.5 AFR average on the O2 sensor.

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You can still tune the idle better IMO. Adjustable air bleeds and fuel restrictors are your friend here, if your carb doesn't have them, consider learning how to add them.
12.5 at cruise/midrange is not doing the engine any favors and the plugs are showing it from the looks of the pictures. The A/F there is a combination of primary jetting and transition depending on your particular carb and RPM.
I would think you'd be real close at a '5' NGK heat range, so like I said maybe I'm just not able to see thread coloring from my end.

The first threads are a little colored, not black but more a dark gold tan from heat.
The idle mixture screws are 1-7/8 turn open, which is too far i guess and i need to get to closing them up.
Although as that changes things again i am afraid i start playing with the wrong thing here.

The screws are that far out to keep the rpm drop within limits when putting the auto tranny in drive.
I've got it to idle at 820-ish rpm and drops of to 700 when in gear.
Also vacuum drops out from 7Hg to 5Hg when putting it in gear.
I was using a 5.5 power valve which i have changed to a 3.5 now and it seems it had done the AFR a bit of good during cruising speeds.

The carb is a Holley Street Avenger 770 with vac. secondary's, it has no adjustable air bleeds and fuel restrictors.
I assume these 2 components are the small brass plugs that can be seen from the top, next to the pump nozzle?

Wietse said:

The first threads are a little colored, not black but more a dark gold tan from heat.
The idle mixture screws are 1-7/8 turn open, which is too far i guess and i need to get to closing them up.
Although as that changes things again i am afraid i start playing with the wrong thing here.

The screws are that far out to keep the rpm drop within limits when putting the auto tranny in drive.
I've got it to idle at 820-ish rpm and drops of to 700 when in gear.
Also vacuum drops out from 7Hg to 5Hg when putting it in gear.
I was using a 5.5 power valve which i have changed to a 3.5 now and it seems it had done the AFR a bit of good during cruising speeds.

The carb is a Holley Street Avenger 770 with vac. secondary's, it has no adjustable air bleeds and fuel restrictors.
I assume these 2 components are the small brass plugs that can be seen from the top, next to the pump nozzle?

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Yes that's them. Some carbs they press them in and that's what you're stuck with. Fine for lots of stuff but when you get into bigger cams etc you really need to be able to tailor the carb to your build. This is done by drilling/tapping but I think you've already gone down that path... I would work with what you can to get it as close as possible and run with it.

I am realizing now i should not have bought this carb, instead pile up money and buy myself a 750 Quick Fuel carb, which has all singing, all dancing installed from factory.
But..when i bought this carb i told myself this is the last carb...next will be EFI.

What's actually stopping me now is a EFI fuel tank with internal pump, to buy one here is expensive, especially on top of a EFI kit.

I will try with what i got indeed for now and start saving up for a full Holley Sniper kit with fuel tank and internal pump.

I have played with the adjustments again, and in the meanwhile checked a tip from a friend about the PCV valve, which pulled too much air from the crankcase in idle due to to low manifold vacuum the engine produces.
This caused my idle mixture to run so lean, even with the mixture screws open far.
Now i am able to idle at 700 rpm, with only 1 turn on the mixture screws which brought down the AFR a bit during cruising speeds.
I had cleaned a spark plug and stuck it back in, this is what i found after some miles.
Think it looks better.

Tell me about what you did regarding the PVC valve.

RobsRR said:

Tell me about what you did regarding the PVC valve.

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My engine only pulls around 7"Hg vacuum at idle, which is low...caused by the camshaft.
My issue is that, with a "general" type PCV valve has 2 positions, depending on vacuum.
Normally when an engine is at idle or cruising speed, the vacuum is high, this pulls the valve inside the PCV all the way up in the housing against a seat.
When it is in this position it causes a restriction, strongly reducing the amount of air that is pulled through and avoids your engine pulling a lot of air from the crankcase at idle/cruise which would lean out the A/F mixture.
The other position of the valve is WOT mode, this is caused by a low manifold vacuum situation like high throttle or WOT.
The valve inside the PCV will be in a "float" situation, not pulled against the upper seat and this results in maximum air flow through the PCV valve to make sure the crankcase is well ventilated from all blow-by gasses.

So, with that being the way it functions, my PCV was allowing full airflow at idle already due to low vacuum and introducing a lot of air, and for that air i had to supply a lot more fuel with the mixture screws to support it but that also makes my cruise mixtures more rich.

I had made a fixed orifice from a 1/2" long piece of threaded bar that fits snug in the PCV hose and drilled a .100" hole in the center and installed it on the carb side of the hose.
Then i set the carb back to basics, trans slot to about square, mix screws 1-1/2 turn open and test run the engine.
I found it idling to slow and too rich, so i removed the orifice again and drilled the hole larger until idle rpm was around 800. (this was with a 3.5mm, 0.138" hole)
It was still running rich so i was able to shut in the mixture screws and lean out the whole range a fair bit.
As a permanent solution i have ordered a M/E Wagner PCV valve, this is an adjustable PCV valve with 2 stages which was developed to get rid of this common issue with bigger cams.
Because now the orifice i installed only allows a certain amount of air, which is ok for idle, but not sufficient during high throttle.
So this is where the Wagner PCV comes in, it will switch to a 2nd stage to allow more air when the vacuum drops below a certain setting.
This is all adjustable and you can tailor it to your engine characteristics.