Electrical Spark Plugs

jimzzilla · Feb 24, 2026

I have a 1988 Mustang, D1SC Procharged 331 stroker motor, Blow Thru Carb, 586 RWHP. The Plugs in cylinders : 1, 4,5,8 run much richer than cylinders 2,3.6.7
I have been told to try a 1 heat range hotter Plug on cylinders 1,4,5,8. I am getting mixed opinions on weather or not to do this.
Anyone tried this, opinions anyone? thank you in advance, James.

86HO5.0 · Feb 24, 2026

Sounds concerning to me. I don't foresee 1 heat range making a big difference/if any on the rich issue.

I'd also be concerned with ignition timing as well. Rich cylinder + more heat=detonation.

gkomo · Feb 24, 2026

I'm no master mechanic, but is it odd that its the fore/aft cylinders only that are running differently? Could that be a sign of something?

86HO5.0 · Feb 24, 2026

What does the AFR look like on both banks throughout the RPM range as well?

jimzzilla · Feb 24, 2026

It's a simple set up, Blo Thru carb, MSD 6AL W/ boost reference Aeromotive A100 FPR. I have AFR meters on each collector bur for meters only.
Lite cruising AFR'S 10 - 10.5 full throttle 14 - 14.5

86HO5.0 · Feb 24, 2026

I hope you meant light cruise 14-14.5 and WOT at 10-10.5.

That looks a bit rich to me. I'd start by leaning it out by 1/2 point across the board.

Noobz347 · Feb 24, 2026

86HO5.0 said:
I hope you meant light cruise 14-14.5 and WOT at 10-10.5.

That looks a bit rich to me. I'd start by leaning it out by 1/2 point across the board.

This would be a good place to start.

You might also consider getting your injectors cleaned and flow tested.

Bullitt347 · Feb 24, 2026

Noobz347 said:
This would be a good place to start.

You might also consider getting your injectors cleaned and flow tested.

"Blow through Carb"...

I don't think cleaning Inj. is going to help. Lol

General karthief · Feb 24, 2026

Check gasket alignment under the carb too. Make sure the boosters are boosting and air passages are passing air.
What brand carb and type of hat?

AeroCoupe · Feb 24, 2026

What is interesting to me is that on a carb setup the four corners are showing fat and the center four are showing lean which I find to be opposite of what most get. Runners on the corners are longer so they tend to get less fuel. This is of course as long as the ignition system is working like it should.

jimzzilla · Feb 25, 2026

Noobz347 said:
This would be a good place to start.

You might also consider getting your injectors cleaned and flow tested.

No injectors, Blo Thru Carb.

jimzzilla · Feb 25, 2026

General karthief said:
Check gasket alignment under the carb too. Make sure the boosters are boosting and air passages are passing air.
What brand carb and type of hat?

jimzzilla · Feb 25, 2026

Ouickfuel blower carb - 650.

jimzzilla · Feb 25, 2026

So has anyone tried installing 1 heat range hotter plugs on the richer cylinders?
I am curious if it can help and can be done or if it is detrimental and not to do it. I have had mixed opinions.

86HO5.0 · Feb 25, 2026

Heat range won't fix a cylinder that is too rich, that is a tuning issue.

The only thing a hotter plug will do is increase its resistance to fouling.

Noobz347 · Feb 25, 2026

Yeah, yah... I missed the carb

86HO5.0 · Feb 25, 2026

Are you running a carb spacer? If so, which one?

General karthief · Feb 25, 2026

Intake type?

jimzzilla · Feb 26, 2026

86HO5.0 said:
Are you running a carb spacer? If so, which one?

I do not remember the brand but it is 3/4'' SPACER.

jimzzilla · Feb 26, 2026

General karthief said:
Intake type?

Vic Jr intake and Vic Jr Heads.

Electrical Spark Plugs

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now i can hopefully expect to receive the shaft

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Stangnet Facilities Maint Tech... Er... Janitor

I have been doing it wrong this whole time

wonder how much it would cost to ship you a pair

lube between the nut and the face. I know my lubes

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Stangnet Facilities Maint Tech... Er... Janitor

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wonder how much it would cost to ship you a pair

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