.060" spark plug gap?

[2112]

OK, I just made the transition to a complete MSD ignition/distributor and I am re-reading the manual and they (MSD) recommend for engines less than 10.5 to 1 compression to run spark plug gaps of .050"-.060".

I have run.035" in everything from 9 to 1 motors to the one 11 to 1 engine (24' Warlock)I had several years ago.

I have to admit I must not fully understand the need to gap the plugs based on compression. I thought it had more to do with plug location in the chamber and whether you have a tight chamber vs. a big chamber.

I am just a tick above 9 to 1 with my current cometic gaskets but I have relatively tight chambers (78cc). Should I be gapping my plugs to .050"-.060"?

[Geronimo36]

Not sure if it matters either but I've been doing .045 on my MSD setup.

[imco offshore]

OK, I just made the transition to a complete MSD ignition/distributor and I am re-reading the manual and they (MSD) recommend for engines less than 10.5 to 1 compression to run spark plug gaps of .050"-.060".

I have run.035" in everything from 9 to 1 motors to the one 11 to 1 engine (24' Warlock)I had several years ago.

I have to admit I must not fully understand the need to gap the plugs based on compression. I thought it had more to do with plug location in the chamber and whether you have a tight chamber vs. a big chamber.

I am just a tick above 9 to 1 with my current cometic gaskets but I have relatively tight chambers (78cc). Should I be gapping my plugs to .050"-.060"?

higher compression can blow out the spark ( so to speek)

[LAKE EFFECT]

I did alot of research last year, but more toward heat ranges with a blower motor combo. I talked to an Autolite tech a couple times, and recall the saying "blowing out the spark", thats where the tighter gap is necessary. All or most of the Autolite racing plugs come with a .025/.035 gap. He also mentioned bigger gaps and emmisions, but did say keep a tighter gap in the boat engines(or any high performance engine) to help prevent misfires.

I would look up Autolite's website or call them. Their AR(racing) plugs have a thick shell, cut back electrodes and a fair price(under $3). They also cover a ton of heat ranges. Plus being a Ford guy, you should know Autolite makes all the Motorcraft plugs.

If I had to guess about MSD wanting a larger gap, I would say that the stronger spark will jump the larger gap, and smaller gaps may wear out a plug faster. But you want no misfires or a loading up condition at idle and such, plus I'm sure new plugs get put in every season, so your not going to wear out a plug.

LE

[JIMG]

when you have higher compression the actual cylinder pressure goes up. this in turn makes the air/fuel mixture more dense. the more dense atmosphere is harder for the spark to jump accross. it is as if it had to jump farther in th open. this is why your spark will jump accross a 1/2" spark checker and only a .040" plug gap. the higher the compression the smaller the gap it can theoretically jump accross.

[DAREDEVIL]

The MSD recomendation is all for car engines,,not for Boat motors.

.35 is a good overall #, in my 12:1 COMPR. Engine i run .35 !!!!!!

[imco offshore]

The MSD recomendation is all for car engines,,not for Boat motors.

.25-.35 is a good overall #, in my 12:1 COMPR. Engine i run .25 !!!!!!

with an msd scott i think i would consider opening up to 35 / 38 and your motor would run cleaner , ( i heard it at sarasota ) pluss u run race fuel

[Geronimo36]

IMCO, I could see the bigger gap helping idle quality with the CD ignition.

When I opened up my gaps from 35 to 45 I noticed less wear/tear on the MSD dist. caps where the rotor hits the coil lead.

I never noticed any differnce in how it ran but did notice the wear on the cap.

[PatriYacht]

10.5 to 1 is considered low compression in the racing world. The plug fires easily over a large gap that low. The higher compression or boost will make it harder to fire so you have to narrow it down from there. I think an MSD will fire almost anything at .035. That said, I gap mine at .040 because the plugs don't look like they were made to have the gap opened any farther. The angle between the electrode and the strap looks wrong.

[Trim'd Up]

I believe Autolite and NGK make plugs for wider gaps.
Regardless, I have always ran .035-.040 in about everything and it seems to work.

[DAREDEVIL]

with an msd scott i think i would consider opening up to 35 / 38 and your motor would run cleaner , ( i heard it at sarasota ) pluss u run race fuel

George,,your right ,,,i run .35 !!!!!!!!! Sorry

[mbam]

We used to test gap on the dyno, open up until misfire than back down .005 or .010, much cleaner low end & idle.

Back in the day there was a gapping pliers that would help keep the ground electrode @ 90 deg.

.045 was where we wound up with the MSD.

[Geronimo36]

.045 was where we wound up with the MSD.

[jeffswav]

I run a Marine DUI HEI distributor at .050 with AC rapid fire plugs. I run 8.9 comp and never had a mis.

[MikeyFIN]

with an msd scott i think i would consider opening up to 35 / 38 and your motor would run cleaner , ( i heard it at sarasota ) pluss u run race fuel

The plugs we put in Clearwater was gapped at .35 and still issues with getting the plugs clogged at the no wake...and yes Race fuel.

If you ask me I would next time open them up to .45

[MikeyFIN]

I run a Marine DUI HEI distributor at .050 with AC rapid fire plugs. I run 8.9 comp and never had a mis.

No wonder with that comp..

[MikeyFIN]

10.5 to 1 is considered low compression in the racing world. The plug fires easily over a large gap that low. The higher compression or boost will make it harder to fire so you have to narrow it down from there. I think an MSD will fire almost anything at .035. That said, I gap mine at .040 because the plugs don't look like they were made to have the gap opened any farther. The angle between the electrode and the strap looks wrong.

And a pump gas engine if you do it carefully.

[Strip Poker 388]

I was told the larger the gap more it put alot of load on the ignition,Its suppose to make a bigger spark.

Just think most plugs are made for around .035, that means your bending the ground electrode up.So it will have a angle .To me if its flat like at 035 it will use all of the flat surface on the center electrode and the same area of the ground electrode,with it bent up I would think it would make ground contact at the edge of the center electrode,being a smaller spark.

Hows that sound

side gap indexed
http://i160.photobucket.com/albums/t...rkPlugDyno.jpg




I don't know if you all remember when MSD came out with there box, they had a test fixture to show the spark.The speed shop here had one on display showing the difference between stock at the MSD,the fixture had a adjustable gap.it would spark around 4 inches,ya could lite you cig with it.

[jeffswav]

No wonder with that comp..

When I set the engine up I thought is was more like 9.3 to 1. However when I switched over to a roller cam RMbuilder ran the numbers and it was really 8.9 to 1 when you figure in gaskets and all the variables. A lot of people probably think their compresion is higher than it really is. We really do not have good enough fuel available to run higher comp anyway.

[DAREDEVIL]

I was told the larger the gap more it put alot of load on the ignition,Its suppose to make a bigger spark.

Just think most plugs are made for around .035, that means your bending the ground electrode up.So it will have a angle .To me if its flat like at 035 it will use all of the flat surface on the center electrode and the same area of the ground electrode,with it bent up I would think it would make ground contact at the edge of the center electrode,being a smaller spark.

Hows that sound

side gap indexed
http://i160.photobucket.com/albums/t...rkPlugDyno.jpg





I don't know if you all remember when MSD came out with there box, they had a test fixture to show the spark.The speed shop here had one on display showing the difference between stock at the MSD,the fixture had a adjustable gap.it would spark around 4 inches,ya could lite you cig with it.

I think the shortest way is what it will look for ,,,smaller spark ??? NO . because the ground is ground no matter where !!!!!!!!

But bigger spark does not mean its hoter and thats what u want.
eficient and hot !!!!!! NOT BIG and all over the place.