Spark plug gaps

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ozmoparjoe

ozmoparjoe

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Hi guys, looking for some advice regarding spark ug gap for my 360.
Engine is 10:1 comp, has MSD ready to run distributor, with MSD blaster 2 coil, and is tunnel rammed.
Spark plugs are BCPR6ES NGK.
What gap do you recommend I run?
Thanks in advance.
 
I don't think you'll see any benefit from going past .045".
 
I run a 7 @ .037 gap and have tried the larger gap from some other theories out there and it doesnt like it in my set up which is 9:5 to 1 408
 
Do me next!

1973 Duster 340, stock piston/cr, 222 SFT, LD340, stock manifolds, MSD Ready to Run distributor, MSD coil.

I’m using #4 Autolites with .038” gap.

Am I on the right track with colder plugs on low compression iron heads? I went a little more gap to get a bigger kernel.

@pittsburghracer @RustyRatRod
 
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go-fish said:
Do me next!

1973 Duster 340, stock piston/cr, 222 SFT, LD340, stock manifolds, MSD Ready to Run distributor, MSD coil.

I’m using #4 Autolites with .038” gap.

Am I on the right track with colder plugs on low compression iron heads? I went a little more gap to get a bigger kernel.

@pittsburghracer @RustyRatRod
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I already told you where I’m at and I run an MSD7AL3. My 72 (340) duster came with electronic ignition. When I told out local Mopar guru that I had to climb a local hill and jump on it in third gear and get two backfires out of it these were his words. Get rid of the damn Champion plugs and put Autolite plugs in it gapped at .028. 40 plus years later I’m at .030

This happened back in the late 1970’s
 
go-fish said:
Do me next!

1973 Duster 340, stock piston/cr, 222 SFT, LD340, stock manifolds, MSD Ready to Run distributor, MSD coil.

I’m using #4 Autolites with .038” gap.

Am I on the right track with colder plugs on low compression iron heads? I went a little more gap to get a bigger kernel.

@pittsburghracer @RustyRatRod
Click to expand...
What do the current plugs LOOK like? They'll tell you all you need to know.
 
pittsburghracer said:
Biggest problem about this is most guys know nothing about tuning a carb.
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I don’t know much but I’ve got my carb tuned pretty good with the help of a good friend.
@RustyRatRod I had a set of plugs in the 340 when I got the non-running car. Engine was freshened by the previous owner but never ran. I started the engine with new plugs, the #4 autolites.
My limited knowledge was leading me to a colder plug for open chamber heads and lower compression. Am I off base here?

I’ll get a plug from each bank and read those when the ice thaws here.
 
go-fish said:
I don’t know much but I’ve got my carb tuned pretty good with the help of a good friend.
@RustyRatRod I had a set of plugs in the 340 when I got the non-running car. Engine was freshened by the previous owner but never ran. I started the engine with new plugs, the #4 autolites.
My limited knowledge was leading me to a colder plug for open chamber heads and lower compression. Am I off base here?

I’ll get a plug from each bank and read those when the ice thaws here.
Click to expand...
You have it backwards as a rule of thumb. Normally more compression will tend to need a colder plug. More compression = more heat and in order to keep that heat in check, you will want a colder plug. But I always go by the "how it runs" and how the plugs look" deal, because there are exceptions to every rule.
 
Lower compression ratio=hotter plug. Should be 5 heat range in NGKs.

I would run 0.060" plug gaps [ yes, 060!!! ] with the RTR dist. The internal module electronics is based on the GM HEI module, which standard used 060 gap [ 080 with some engines! ], & your low CR allows for bigger plug gaps.
 
in my stocker, with msd 7al, run .060 gaps, also, use a standard length plug, not a extended tip plugs, also can run more timing , this is a 72 340. at track , opened up gaps from .045 to .060 ran .05 faster and .75 mph faster. btw, i use NGK plugs. just food for thought. btw it's a B8es plug
 
Sometimes a bigger plug gap does not increase peak hp......but it can certainly improve idle quality & drivability.....
 
perfacar said:
in my stocker, with msd 7al, run .060 gaps, also, use a standard length plug, not a extended tip plugs, also can run more timing , this is a 72 340. at track , opened up gaps from .045 to .060 ran .05 faster and .75 mph faster. btw, i use NGK plugs. just food for thought. btw it's a B8es plug
Click to expand...

Do you mind me asking what this car runs
 
I tried opening the plug gap on my 410 as Bewy recommended to 50 thou! It idled a little bit better and was a tad more responsive down low but on full throttle @ over 6000rpm it would backfire badly. I did not cure that back fire until I closed the gaps up to under about 40 thou. My 410 has 11/1 compression. And runs NGK plugs!
 
You autolite guys... are you running the Autolite 5224 in your small block daily drivers? Or the Autolite 65? I'm not talking race car with high compression, I'm talking in your stock 318 or 360 in your daily.....
 
318willrun said:
You autolite guys... are you running the Autolite 5224 in your small block daily drivers? Or the Autolite 65? I'm not talking race car with high compression, I'm talking in your stock 318 or 360 in your daily.....
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My bad. Not Autolite.

AC Delco Iridium, 19307141. All the other info is the same, 73 low compression 340 with only non-stock components is LD340 and R2R MsD.

Car runs good. Carb was tuned with these plugs and gaps but during tuning we didn’t consider the plugs.

I’ll definitely try a hotter plug in the NGK and start at .045, which is just .007 more than now.

I have always understood that heat ranges vary between mfg. but anyone know how much AC/D and NGK are apart from each other?

IMG_8059.jpeg
 
Iron head, mainly because an aluminium one would be a bespoke job with a bespoke price, its an australian I6 engine, semi hemi combustion chambers and a static CR of 12:1 DCR of 8.something :1

i basically tried to build a 340 like thing, out of a motor that was nothing like a 340 with a nod to I4 tuning i.e webers and a set of headers that are smaller and longer than you would expect.

i wanted rev happy with decent torque and the fun over and done with by 6500

cut 60 thou off the head :)
and 40 thou in a band off the edge of the crown

luck necessity and budget rather than true judgement and planning were involved in this build.

it works..i like it

dave
 
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318willrun said:
You autolite guys... are you running the Autolite 5224 in your small block daily drivers? Or the Autolite 65? I'm not talking race car with high compression, I'm talking in your stock 318 or 360 in your daily.....
Click to expand...
I run Autolite 65 plugs in my 340 car. It's a 10.3:1 compression w/cast iron heads. Still running the dual point. They last forever.
 
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