Club Cobra - Spark Plug Gap- Poll

Club Cobra (http://www.clubcobra.com/forums/)

- Small Block Talk (http://www.clubcobra.com/forums/small-block-talk/)

- - Spark Plug Gap- Poll (http://www.clubcobra.com/forums/small-block-talk/91755-spark-plug-gap-poll.html)

Spark Plug Gap- Poll

I had the idea to open up some basic topics to help the newbies / non-wrench turners to care for their cobras.

In so, getting a sense of SBF spark plug gaps, and what they run in.

-- in my experience;

with a points ignition systems in small block ford, a plug gap of .032 to .035" is fucntional for a stock distributor (points type) and a stock coil.

if you add a magnetic trigger (pertronix) to the distributor and a hotter coil that can allow you to open up the spark plug gap to .035-.038"

If you run a duraspark or HEI you can open the gap to .045-.049 depending on camshaft, carb and timing.

With an MSD or other type of capacitive (multi) spark discharge box, that can avail you to open the gap up .044-.059 depending on many factors.

In my experience, the narrower the plug gap - the smoother the idle can be, but this will take away from power at upper rpms. also there can be to-wide of a gap causing the engine to have a rattly idle and not feel like pulling under load, like a miss' under load.

-- open for other to add their experience!

--Steve

MSD... .045 autolite 3924. 351/427w

MSD Distributor, MSD-6T box(Analog), UR5 NGK plugs @ .045 gap, 289 with 48 IDA's

Mallory unilite + Mallory 6A, NGK BCP6 @ .045 gap, 347 4 x 48IDF.
RS

.032 " (0,8mm) after reading high A/F (10- 12) and advice from a guy. Saying high compression pressures also should have smaller gap.

Does it work better? Time will tell.

.039/.042 with a Jacobs Pro Racing unit. But since Jacobs is no longer worth anything I will be changing to another type unit one of these days. Also stay away from he Platinum plugs if you do have a Jacobs.I tried them once and it ran crappy as they threw off the resistance readings.

Ron

Hi,
Any high peformance engine with high compression, or power adder I tell to set gap at .035. It's best to get the spark than a misfire. Large plug gaps also burn out ignition wires. You can see wires that are like new but burned near the cap. They have a brown tinge to them.
Large plug gaps are for low performnce emissions engines.
I remember in the late 70's misfires at the rotor shorting to the distributor shaft....
Think of it as a .22 hit is better than a .45 miss...

I'll install my new Denso- equivalent of NGK BCP7E at .035" this evening.

Maybe same thing will happen as when I changed from 5'ers to 6'ers?

M.S.D. with E3 plugs, 3 tips, no gapping, no problem.

Mallory 6AL Autolite 3924 .040 gap

Stock 289 Hi-Po , 10:1 compression w/ MSD Digital 6, Autolite 45's gapped @ .45

same as above with vintage Paxton (6 lbs. psi maximum), Autolite 45's gapped @ .28

Z. Ray

FE, Champion RC12YC, .032, 10:1, MSD.