Hot Rods Flathead spark plug question

I have been having problems fouling out plugs in my 40 going to try NGK this time and want to know what gap works best?

My setup is 50 Merc motor 400jr cam Edelbrock 2x2 with new 97's been running Autolite 216 @ .32 gap, It is 12 volt and dual point dizzy. Also still running Orig Heads.

HELP!!!

I get 30 miles on a set of plugs, then they are trash! The old worn out 8BA I took out never fouled a plug and I drove it all over the place, even to Austin and back without any issues. I am ready to BLOW this thing up!

 

Ngk B6L are good to go but my flatly seems to run stronger on Ngk B4L.

 

I know I may need to back off the jet size in the carbs as well but want to get the rest right first.

 

Yes I got B-6L this time.

 

Surly there is Flathead experts on here that know more than me.

 

Personally I'd stick with .025" gap. Even with a Pertronix or MSD that's what most people run. There's no big advantage to a wider gap.

 

Anybody else? Does this make sense? Never had a SBC cause me so many seemingly simple problems!

 

B6L at 25 thou works for me.

 

Why not try the Fordbarn?

 

My 36 coupe has 8BA flathead Isky 400 cam 2 x 97s, I was having plug issues switched to Autolight 303 there 1/16" shorter but I have put 2,000 miles on them with no issues. Your engine is the same as mine except I'm running a Vertex mag.

 

Its still a flathead so run between .025 and .030 ask Bubba. I have a basically a stock motor with 12 volt and electronic ign. I run .030 NGK's AB6

 

According to MSD that is incorrect information.
Read this....
http://www.jalopyjournal.com/forum/showthread.php?t=810297

Instead of looking for a sparkplug to fix your engine problem go back to basics. Fuel, compression, timing and ignition. Your problem lies in one of these areas. Flatheads don't normally foul plugs when everything is in order.

 

Your plug gap depends on the coil voltage and really nothing else.

When in doubt, a matchbook cover thickness will usually do the trick. Good luck finding a book of matches today.

 

As I said, not running electronic but dual point. I get 30 miles on a set of plugs!!

 

Are your plugs fouled with gas or oil?
Is this a fresh rebuilt engine? If so maybe the rings aren't seated.
I have had very good luck with autolite plugs. Champions not so much....

 

Maybe the new 97s are setup to rich.

 

Don't blame the plugs. Tune your engine properly.

 

Get yourself a set of adjustable jets for the 97s...

 

Like the others said , fix your rich fuel problem and the plugs will do ok.
.025 gap is what works the best in the flathead, extending the gap ( wider) on the flathead is nothing but trouble especially on the stock distributor. The rotor spacing from tip to case is very small compared to other ignitions.

 

I'm running NGK B6L's in a stock '52 EAB with a single 94,Bubba's distributor,plugs gapped at .025 been in for a year now with 4000 miles on them with no problems.

 

Lean out the carbs,make sure the coil is strong enough.

 

It's somewhat like an archer blaming the arrow! Sounds like a fuel problem... how much fuel pressure? Those old 97's and 48's usually don't want more than 2.5 #'s or so. In my experience once they are fouled they won't recover. g

 

They are talking about ignitions with their 6A-type control box. I should have been clear, I meant an MSD electronic distributor. Even with a 6A system there's just no benefit to a wide gap on a flatty. Not many people are running lean mixtures in flatheads.

I agree it sounds like something's wrong on the mixture or rings, but if it is mis-firing due to the wide gap, it would look the same.

 

I encountered the same problem - 99A, two 97's, Offy standard dual intake, aluminum heads. The problem was not ignition, plug heat range or gap. I jetted all the way down to .040, tried combinations of main jets, couldn't find smaller idle tubes, tried different float levels, hotter plugs. Leaning the carbs helped only to a degree, but when the plugs cleaned up, the mixture was too lean and drivabilty really suffered. The problem was the carb linkage - opening both carbs together. If you have two carbs opening together, you are effectively doubling the size of the carburetor and the RPM at which you're still running on the idle circuit or transition circuit ( each carb is only getting half the air volume and thinks the rpm is half of what it is). The idle circuit is jetted way richer than the main circuit. The main jets may not come into play until maybe 1500 -2000 RPM. Most of my driving was around town under 2000 RPM, hence the constantly sooty plugs. Lowering the float level had the most effect on leaning the idle mixture but was never satisfactory. I finally designed an adjustable progressive linkage which let me use the front carb for most driving under 2000 RPM. When the rear carb opens, it is at a high enough RPM and opens twice as quickly so it's on the main jets much sooner. I have an .045 main jet in the front carb, and an .044 in the rear. everything else is set to stock specs in the carbs. The accelerator pumps are on summer, and both idle circuits are intact and adjusted. I 'm running 2PSI fuel pressure, 180° thermostats, B4Ls at .025 and they look spectacular after not having been touched in 1000 miles. I hope this gives you another direction to go in solving you problem.

 

you have to make sure your carbs are tuned properly otherwise no matter what plug you throw in it will foul out its quite simple just my 2 cents

 

What exactly is your distributor...converted stocker, MSD, new Mallory, antique Mallory? Advance issues can also mess up your plugs very rapidly.
Mixture...what jets? New Strombergs---real or Speedway?
If normal good Strombergs, jets are probably not the issue. The standard 97 jets and power valves MIGHT be slightly too rich for optimum, but they would not be stinking rich kill the plugs in 30 miles rich.
If this seems to be truly a mixture issue, look up top: Do you have the normal 2 little chrome aircleaners?? If so, FIRST IMMEDIATE thing is to take them off and go for a drive. See what that does for the plugs.