Another Spark Plug Gap Thread.... LOL

[Vbb199]

If you know about the title, we can be friends.

Curious what peoples takes on plug gaps are? No, my truck isnt broke down, and if i dont gap mine correctly, ill cry and throw a fit if someone doesnt answer within the next 10 minutes.

I'm not asking for stock configuration input (sorry )

Im asking what you guys run on your highly modified motors or slightly modified, with adders like ignition boxes, coils, etc etc.
Im running a large gap, ignition box, 30k coil, on a 10.5 motor, running on 93 octane.
Motor runs like a scalded dog, and sounds throaty and mean, pulls hard, overall, im satisfied from an ancient TBI system. I'll be even more satisifed once my modded 46mm tbi is installed i machined up a couple weeks back.

I was just pondering today maybe after work, playing with plug gaps and doing runs down the road.

The purpose here isnt intended to discuss MY setup, its to hear YOUR setup whether youre running a blaster coil, MSD, etc etc.


With the input i get, ill get a general consensus and aim for that first as part of my tests.
Let me/us know your setup!

 

[Vbb199]

My purpose here is, the internet tells many many variations of stories.
One side says you can basically take a stock ign system, put a big gap on your stock motor, and make 1,000,000 horsepower. I know thats fraudulent, and im exaggerating.

Another side says, keep a tight .035-.045 gap if youre under like, 700hp, n/a, even with a ignition box and coil.

Im wanting to see what YOUR input is on YOUR motor.

**the only requirement here is, no LS motors (totally different system from a distributor driven system), and no induction motors. Just wanting raw naturally aspirated bbc and sbc data
Thanks guys

 

[AuroraGirl]

I had .6 amd up gap on 46 plugs and heavily retarded base timing

it wasn’t a good setup nor would I recommend ever doing it

 

[legopnuematic]

My 76 I run with HEI (0.040 over mild 350) at .045, when I had the MSD setup I was running somewhere closer to 0.055-0.060, works fine with both.

From what I understand is that spark plug gap is based on what your coil is able to throw without pushing it too hard and overheating it and where it wont blow itself out.

So a smaller gap will be more reliable and better for older/unknown ignition systems in a more "industrial" (in the sense of put it in the engine and run it till it doesn't work no mo) application

Likely wont make any appreciable difference in 90% of engines out there.

I'll throw a zinger in, what about sidegapping and plug indexing?

 

[Vbb199]

My 76 I run with HEI (0.040 over mild 350) at .045, when I had the MSD setup I was running somewhere closer to 0.055-0.060, works fine with both.

From what I understand is that spark plug gap is based on what your coil is able to throw without pushing it too hard and overheating it and where it wont blow itself out.

So a smaller gap will be more reliable and better for older/unknown ignition systems in a more "industrial" (in the sense of put it in the engine and run it till it doesn't work no mo) application

Likely wont make any appreciable difference in 90% of engines out there.

I'll throw a zinger in, what about sidegapping and plug indexing?

I was gonna sidegap mine should i have time. But yes, id like input in thar also.

I too am running a .060 gap with my coil and box.

Was considering going to slightly above stock (.035) to a .045 and see results

 

[Ricko1966]

I've side gapped, I've indexed, run gaps all over the board too much gap causes a stumble IDK why. And kills modules.And of course too little gap your not gonna light a good fire. HP coils and modules are a waste of money IMHO. If it takes 30,000 volts to light the fire a 100,000 volts doesn't light it anymore.Gap and compression will dictate coil selection and non of us are running enough of either to get any appreciable benefit from non oem parts, and AC Delco ignition components are fantastic. I use.040 on everything I run copper cores and change them regularly.

 

[Snoots]

.035 was great for points distributors, .045 works great for HEI. I've known guys that ran .060 that had MSD boxes but went thru boxes. I guess they had a money tree.

I ran HEI at .035 for a short while, they fouled out quickly. I run AC R45TS' at .045 in a mild rebuild on regular gas.

 

[Ricko1966]

If you're playing just for the sake of playing, I'd drop 1 heat range and throw 2 degrees more timing at it.

 

[Vbb199]

If you're playing just for the sake of playing, I'd drop 1 heat range and throw 2 degrees more timing at it.

With the PROM chip i have that added a couple degrees of total timing, plus im advanced 2 more degrees above stock, my total timing is damn close to detonation. As i learned this weekend while pulling a little over 6,000 pounds, i actually need to go down just a tad in timing. It was pinging going uphill from a stop.

 

[Bextreme04]

Realistically most of these engines would prefer .060, but the coils can't support the amount of voltage required to reliably fire that big of a gap. The CNP setup on the newer engines lets the coils take longer to charge and more reliably fire the plugs, which is why they run a .060 gap with iridium plugs from the factory and can go 100,000 miles with no maintenance.

If you look at engines that have both standard distributor systems and CNP system variants, you can tell that it isn't the engine itself that is the deciding factor on plug gap. For example, L29 Gen VI 454 using the vortec distributor(computer controlled), 9:1 compression, MPFI, runs .045 gap platinum plugs factory. L21 Gen VI 454 is the EXACT same engine with forged internals, CNP ignition, 9:1 compression, MPFI, runs .060 gap iridium plugs.

 

[Vbb199]

Realistically most of these engines would prefer .060, but the coils can't support the amount of voltage required to reliably fire that big of a gap. The CNP setup on the newer engines lets the coils take longer to charge and more reliably fire the plugs, which is why they run a .060 gap with iridium plugs from the factory and can go 100,000 miles with no maintenance.

If you look at engines that have both standard distributor systems and CNP system variants, you can tell that it isn't the engine itself that is the deciding factor on plug gap. For example, L29 Gen VI 454 using the vortec distributor(computer controlled), 9:1 compression, MPFI, runs .045 gap platinum plugs factory. L21 Gen VI 454 is the EXACT same engine with forged internals, CNP ignition, 9:1 compression, MPFI, runs .060 gap iridium plugs.

Good point there, i dont totally understand ignition, but i always understood to some capacity n/a or induction played roll, (induction requiring small gap, high voltage).
Where a standard naturally apirated motor depended on compression.

(14:1 i.e. necessitating a large gap and high energy with some actual amperage to ignite it)

 

[Ricko1966]

With the PROM chip i have that added a couple degrees of total timing, plus im advanced 2 more degrees above stock, my total timing is damn close to detonation. As i learned this weekend while pulling a little over 6,000 pounds, i actually need to go down just a tad in timing. It was pinging going uphill from a stop.

That was why I said drop 1 heat range, now that I know you have preignition definitely drop 1 heat range and see if it goes away. How many pin ignition module are you running?

 

[Vbb199]

That was why I said drop 1 heat range, now that I know you have preignition definitely drop 1 heat range and see if it goes away. How many pin ignition module are you running?

2 pin, electronic advance distributor.

Forgive me, What do you mean heat range? Plug gap?

 

[Ricko1966]

2 pin, electronic advance distributor.

Forgive me, What do you mean heat range? Plug gap?

Spark plugs come in heat ranges hotter and colder.The manufacturers all use their own numbering system some as the number goes up the heat goes down, and vice versa.Anyway 1 range colder as long as they do not foul is a cheap way to try to bring down preignition.As for module under the cap is it a 4 pin a 5 pin or a 7 pin. If it's 4 pin you can make a poormans knock sensor real cheap you replace the 4 pin with a 5 pin I think it was ac/delco 1941 module when 5th pin is grounded it pulls 4 degrees of timing out rig the 5th to ground how ever you want to momentary contact switch, toggle switch etc. Now you can bump timing if you only have ping at limited times and when your in those times ground the 5th pin.

 

[Vbb199]

Spark its come in heat ranges hotter and colder.The manufacturers all use their own numbering system some as the number goes up the heat goes down, and vice versa.Anyway 1 range colder as long as they do not foul is a cheap way to try to bring down preignition.As for module under the cap is it a 4 pin a 5 pin or a 7 pin. If it's 4 pin you can make a poormans knock sensor real cheap you replace the 4 pin with a 5 pin I think it was ac/delco 1941 module when 5th pin is grounded it pulls 4 degrees of timing out rig the 5th to ground how ever you want to momentary contact switch, toggle switch etc. Now you can bump timing if you only have ping at limited times and when your in those times ground the 5th pin.

2 pin, its TBI, electronic advance. No vac or mechanical advance.
Has a knock sensor in the side of the block with the use of a ESC module for retarding timing upon preignition.

ECM does a selftest every time on startup for pinging.
It increases timing until it recieves a ping at the KS, if all works as well, it continues on doing tests at other sensors.

If it fails, it sets code 42 or code 43.