What do you guys think I should run my plug gap at? I have a 352 with an Edelbrock 600 cfm, stock 4 bbl intake, Heddman Hedders, Petronix Ignitor, and a Flamethrower coil. I have them set at .040 right now and it just doesn't seem right to me.

 

What plug are you using? Try .045". Check your timing.

 

chissler! I like your attitude! Welcome to FTE.

 

I'm using the NGK V-groove plugs. I'll try going to .045 when the weather lightens up a little bit. How will I know what I get my gap too wide?

 

When the gap is too wide, you will be stress testing the insulation on the secondary side. You also increase the posibility of crossfire. There is no reason to go above .050.

 

Why not go above 050 plug gaps ? If the secondary wires are in good shape, they can handle it fine. I'm running .080 with Autolite plugs without any trouble. I have found the bigger gaps help smooth out the idleing with my bigger cam. DF

 

Do you think it will help to run higher gap with my setup?

Cam Specs:

http://www.thedreyerfamily.com/69f250/camspecs.htm

See sig for other hardware

 

Testing has shown that beyond .050 gaps, the measurable improvements in combustion quality are very small. The wide gaps increase the resistence in each secondary lead. The spark will have difficulty jumping the wide gap at the plug.

The higher voltage will seek a path to ground that has less resistence then the plug gap. Any imperfection in the cap or wires will result in misfire or the possibility of crossfire which can destroy an engine.

Since the gains of a wide gap are small in relation to the problems of maintaining the insulation required, there is no point in running the wide gaps.

 

To be honest, I'm not even sure where I'm running. I'll guess I'll shoot for .045 or .05 when I next pull the plugs.

 

William, I have to disagree. I think bigger is better when it comes to spark gap. I would very much like to study any testing of plug gap size on engine performance. Do you know of any tests I can read about ? My thinking is this....A bigger gap has more of the mixture exposed to the arc, and is more likely to light the burn. I would imagine that .125-.250 plug gaps might have some really interesting abilities for lean mixtures. However, the whole deal is a compromise, the bigger the gap, the more voltage required to jump it. And Voltage is only part of the picture. There is also the issue of how much amperage gets pushed over the plugs, more is better here, but more amps thru the plug also makes the electrodes erode faster. But, the more power you run through the system, the more beefy ( and more exspensive ) the wires and everything else have to be. There is also the issue of 'punch through', where the arc turns the mixture in the chamber to some kind of plasma, and no ignition of the mixture occurs. How much is too much, I don't know. Points run at about 2 1/2 amps, Duraspark and other factory ignitions run about 4, my Jacobs computer runs at 16. I think the points guys should run .040, electronics, .060; and the computer guys can run at least .080. It never occured to me to try anything bigger. I started with my current setup for ignition on an old 352 that needed a rebuild and burned alot of oil. It worked very well, so I stuck with it. What igntion system was used in the test you mentioned ? DF

 

I'm not William but I will try to respond. I was going by comments in David Vizard's book " How to build and tune cars for performance and economy ". He seems to know what he is talking about. I did find a comment by Smokey Yunick ( too bad he didn't work on Ford engines). He said that with a multi coil ignition, you could go up to .100 gaps and maybe produce more power.

With multi coils the secondary leads are 3-4 inches long. This prevents crossfire. He makes a point that with a distributor system you must maintain at least .5 inches from other plug wires and ground.

 

Be careful if you have an EDIS, 2 plugs fire together, and in series.
So, the effective gap is 2X!!!

 

I am at a loose 60 right now. I recently pulled the plugs because I thought that after 30000 miles they would be needing a change. Well surprise, they were clean and not worn a bit. I put them back in. My truck runs really good, uses a bit of oil but doesn't smoke on the road? I have a new engine on the stand and it will be going in ASAP!. I like the big gap 9.5 CR and a little rich on the Edelbrock but for now 60 is good enough. I run a pertronix Ignitor and a mallory coil. I have wire seperators on the plug wires and extra space around #7 and 8. Later just for the heck of it I will try 80! Right now I am busy planning Sadams demise.