Side Gapping

Grumpy has been busy and has me thinking again. A couple of guys I know run side gapped plugs but no "proof" that they get better performance...no dyno.

Anyhow, I use ACDelco R43T for my BB. Good old reliable. They are still under $2 a plug.

Any of you guys side gapping? Just how do you side gap? I read in Grumpy's article that you straiten the arm, cut with dremel and then bend back. What gap do you then put on the arm? .035? This right?

I normally change plugs once a year whether they need it or not. So spending 16bucks is no big deal if I screw them up. I think I'll give it a shot before I start messing with my carb settings to see if I can get any more performance.

I think I'm going to try it

Seems kind of hard to get them all exact though

I may try a hotter plug too

Just found another article that says to Gap it with a feeler guage minus .010 from the manufacturer specs....ie .035 down to .034 for my engine.

Yellow73SB said:

I think I'm going to try it

Seems kind of hard to get them all exact though

I may try a hotter plug too

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Would it make much of a difference if they are not all exact? Gap will still be the same for all plugs.

Yeah I guess it wouldn't matter much

SmokinBBC said:

Just found another article that says to Gap it with a feeler guage minus .010 from the manufacturer specs....ie .035 down to .034 for my engine.

Click to expand...

???

My math says that .035 less .010 is .025? Not surprised if my math is fubar, (it usually is.....)

I think that's a pretty small gap. Autolite makes an AR series plug that has the side gap already cut. I had a couple sets in Ol' Red-- didn't last very long. But then, plain old plugs don't either..

TimAT said:

SmokinBBC said:

Just found another article that says to Gap it with a feeler guage minus .010 from the manufacturer specs....ie .035 down to .034 for my engine.

Click to expand...

???

My math says that .035 less .010 is .025? Not surprised if my math is fubar, (it usually is.....)

I think that's a pretty small gap. Autolite makes an AR series plug that has the side gap already cut. I had a couple sets in Ol' Red-- didn't last very long. But then, plain old plugs don't either..

Click to expand...

My math is fubar...haha! :clobbered:

I can order the Autolite AR from AZ...2.68 each. Not bad.

I've never run side gap plugs, but my first thought is about the increased kV requirements to fire that setup. If the center electrode has to fire sideways to the ground electrode, the "blunt" side is the path, versus the "sharp" point at the center. Probably not a big deal, but theoretically it looks like additional voltage would be required to jump that, assuming equal gaps.

It doesn't fire sideways, it fires ....how to explain... at an angle. You sidegap the electrode but not to the side but actually sort of diagonally. Kind of hard to explain, this pic will help:



See how the ground electrode is not sideways from the center electrode?

Theory is, it unshrouds the spark, however I have run them quite a few times and IMO it's a lot of work for no gain. Didn't notice any difference, well...actually I did, see as the electrodes wear the gap becomes larger this way, not so with a std. plug. In that respect you'll be swapping plugs more often.

TT, how good does that cut have to be? Right on the edge of the kernal..or is being off erring on the side of the kernal ok? I plan on marking the cut and then covering the top of the plug with masking tape so as not to get any filings down in the plug. The plug will be held in a vise..cutting with dremel.

I've got the plugs and nothing better to do today, so I'm going to give it a shot

69427 said:

I've never run side gap plugs, but my first thought is about the increased kV requirements to fire that setup. If the center electrode has to fire sideways to the ground electrode, the "blunt" side is the path, versus the "sharp" point at the center. Probably not a big deal, but theoretically it looks like additional voltage would be required to jump that, assuming equal gaps.

Click to expand...

I'm with you. Higher voltages love pointed areas, IE, lightning rods are pointed. The new RadidFire plugs are pointed. I cannot see any advantage to a side gap, but welcome the results of a controlled test.

I just did the first plug. Had to put the dremel in the vice and hold the plug....my hands were just not steady enough to hold the dremel. Really not that big of a deal to cut them.

I agree with you guys on the controlled test...I'm not going to cut any more plugs right now since I have no way of knowing whether this will provide any improvement.

But....I am going to be doing some dyno tuning for the carb this fall with some friends. Where going to "buy" the shop and dyno guy for half or full day. Maybe what I'll do is get the autolite AR plugs(only 2.68 each) and put those in on the second run so I can see the change from the base for the plugs alone....that is if I can change the plugs on the passenger side without getting 1st degree burns. :crutches: We'll see. As for a controlled test for MPG....well, that will never happen

big2bird said:

69427 said:

I've never run side gap plugs, but my first thought is about the increased kV requirements to fire that setup. If the center electrode has to fire sideways to the ground electrode, the "blunt" side is the path, versus the "sharp" point at the center. Probably not a big deal, but theoretically it looks like additional voltage would be required to jump that, assuming equal gaps.

Click to expand...

I'm with you. Higher voltages love pointed areas, IE, lightning rods are pointed. The new RadidFire plugs are pointed. I cannot see any advantage to a side gap, but welcome the results of a controlled test.

Click to expand...

I don't think the benefit comes from where the spark initially hits so much as to where it travels after it hits. No?

SmokinBBC said:

I just did the first plug. Had to put the dremel in the vice and hold the plug....my hands were just not steady enough to hold the dremel. Really not that big of a deal to cut them.

I agree with you guys on the controlled test...I'm not going to cut any more plugs right now since I have no way of knowing whether this will provide any improvement.

But....I am going to be doing some dyno tuning for the carb this fall with some friends. Where going to "buy" the shop and dyno guy for half or full day. Maybe what I'll do is get the autolite AR plugs(only 2.68 each) and put those in on the second run so I can see the change from the base for the plugs alone....that is if I can change the plugs on the passenger side without getting 1st degree burns. :crutches: We'll see. As for a controlled test for MPG....well, that will never happen

Click to expand...

I'm betting you will not see much of a difference in HP. Most dynos have a error of + or - 2%. That can be as much as 4 hp per 100 hp. Just my .03 cents. :drink:

I use a cut-off disk on a dremel to cut mine,(generally just a smidge of overlap, just a bit longer than the picture so it overhangs about 1/3 of the way accross the tip)
your NOT going to notice an improvement UNLESS everything else is darn near perfect on your cars tune, and its tunned for max power, (MAX USEABLE CYLINDER PRESSURE)
that generally means open headers, decent scavaging, and about a 12.7:1 fuel air ratio and the ignition curve advance just short of getting into minor detonation, (usually full advance of about 36-38 degrees all in at 3100rpm)the idea is to allow a faster flame front in the cylinder with the max cylinder pressures, and the most effective f/a ratio is generally near 12.5-12.7:1, so keep that in mind before thinking your not getting any change when testing
IF your running a 14.7:1 economy f/a ratio youll probably get little if any improvement on the lean burn

Grumpy, the main reason for the dyno tune is the carb is running a little rich.

The AFR at idle is about 13.7 to 14. Idle speed=675-685
AFR at cruise is 13.0 to 13.2.
AFR at WOT is initially 10-11 (pump shot effect?) and then climbs to about 12 to 12.5.
The spark plugs look good, perhaps a little dark/rich.

I had a deiseling problem. That is why I have a fat idle mixture and low idle speed(it's an MT).


So If I interpret you last statement right...."IF your running a 14.7:1 economy f/a ratio youll probably get little if any improvement on the lean burn " I should see improvement if I do it now since I am not running a lean mixture.

if youve got enough voltage and a decent strong blue spark , with that f/a ratio you should see a slight improvement in responce and power, now were not talking seat of the pants and an extra 30 feet of rubber on the pavement but a couple of hundeths faster in the 1/4 mile is certainly reasonable

grumpyvette said:

if youve got enough voltage and a decent strong blue spark , with that f/a ratio you should see a slight improvement in responce and power, now were not talking seat of the pants and an extra 30 feet of rubber on the pavement but a couple of hundeths faster in the 1/4 mile is certainly reasonable

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Does a stock ignition (1970 BB) set-up fall into the enough voltage category?

Im sure you realize the stock chevy 1970 ignition is usually marginal,as far a high performance ignition goes, but yes it should work if its functioning correctly. Im sure your aware there better plug wires, and higher volt coils ETC.

grumpyvette said:

Im sure you realize the stock chevy 1970 ignition is usually marginal,as far a high performance ignition goes, but yes it should work if its functioning correctly. Im sure your aware there better plug wires, and higher volt coils ETC.

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The setup works well right now. I pull 5000+ without any problems. It is hyd roller engine and can rev higher. I have looked into upgrading the ignition, but see no point right now since the stock one looks to be running pretty good.

Thanks for all the input guys!