jimbo95Z28

Which would you reccomend?
I am going to start off with a 50-75 shot , and eventually go 100 shot on the street. I will get up to a 150 at the track, but I rarely go to the track.Just let me know what you think is better.

drop top steve

AC Delco R42LTS, indexed, and side gaped at .040. this is for a 150 shot. This as the same heat range as a Autolite 103 or an NGK BR7EF, a TR6 would be one range hotter.

Alan566

drop top steve,
what does indexed mean? sorry if thats a dumb question. I am running the same plugs and gapped at 38 just notted sure about the indexed part. Thanks Alan

BAD 97 WS-6

Naturally aspirated. the Autolite 103's gave me 2 mph quicker in the quarter than 104's. That might be because I am running 11.2 compression though. I am not sure, but the car is definately quicker with 103's

396LT192

I usually use 103's. Right now I actually am using stock heat range NGK's but I put a 50/50 race gas mix for the 150 shot.

drop top steve

Indexing is controlling the direction the ground strap points. You want the open side of the plug aimed at the center of the piston. Looking down on top the engine the ground strap should be at the top, from 11-1 o'clock postion, I like to aim the spark toward the intake side of center. This aids in flame travel. Side gapping is just grinding the ground strap down till the end is centered with the electrod. Doing this MIGHT give you 4 or 5 HP. It's old habit with me from running large dome pistons that would coillid with the ground strap if the plug was not indexed, 14/1 or higher compression, drag race only using alcohol as fuel.
They make washers .010, .021, and .032 thickness for getting the index right.

385LT1

NGK V- POWER


NGK PN# TR55 SN# 3951 V-POWER LT1 STOCK HEAT RANGE W/ .060 GAP

NGK PN# TR5 SN# 2238 V-POWER LT1 STOCK HEAT RANGE W/ .035 GAP

NGK PN# TR6 SN# 4177 V-POWER LT1 2 #'ers COLDER THAN STOCK HEAT RANGE W/ .035 GAP

NOTE: BOTH LT1 & LS1 14MM THREAD DIAMETER / .708" THREAD LENGTH / TAPERED SEAT


LT1 STOCK HEAT RANGE = 1 HEAT RANGE HOTTER THAN LS1
LS1 STOCK HEAT RANGE = 1 HEAT RANGE COLDER THAN LT1
EX: TR6 = 1 HEAT RANGE COLDER THAN STOCK LS1
EX: TR6 = 2 HEAT RANGE'S COLDER THAN LT1

AUTOLITE HEAT RANGE CHART
(AUTOLITE 104 IS LS1 OEM REPLACMENT)
(AUTOLITE 106 IS LT1 OEM REPLACMENT)

NKG SPARK PLUGS

5. Heat Range selection

Let's make this really simple: when you need your engine to run a little cooler, run a colder plug. When you need your engine to run a little hotter, run a hotter spark plug. However, NGK strongly cautions people that going to a hotter spark plug can sometimes mask a serious symptom of another problem that can lead to engine damage. Be very careful with heat ranges. Seek professional guidance if you are unsure.

With modified engines (those engines that have increased their compression) more heat is a by-product of the added power that normally comes with increased compression. In short, select one heat range colder for every 75-100 hp you add, or when you significantly raise compression(SEE NOTE *). Also remember to retard the timing a little and to increase fuel enrichment and octane. These tips are critical when adding forced induction (turbos, superchargers or nitrous kits), and failure to address ALL of these areas will virtually guarantee engine damage.

An engine that has poor oil control can sometimes mask the symptom temporarily by running a slightly hotter spark plug. While this is a "Band-Aid" approach, it is one of the only examples of when and why one would select a hotter spark plug.




* NOTE:

With this in mind, just becaue you have stock internals, doesnt automatically exempt you from needing a colder spark plug...
Any modification that creates a higher power output needs to be considered.

So, 1995 385 LT1 with over 500 fwhp
stock = 275 hp

500-275 = 225 over stock

Plug = NGK TR6 2 heat ranges colder than stock...
with the 1 heat range colder for every 100 hp rule...

This doesnt really add up if you run a power adder,
but people are running them successfully on these
plugs....

385LT1

3. Gapping

Since the gap size has a direct affect on the spark plug's tip temperature(note*) and on the voltage necessary to ionize (light) the air/fuel mixture, careful attention is required. While it is a popular misconception that plugs are pre-gapped from the factory, the fact remains that the gap must be adjusted for the vehicle that the spark plug is intended for. Those with modified engines must remember that a modified engine with higher compression or forced induction will typically require a smaller gap setting, to ensure ignitability in these denser air/fuel mixtures. As a rule, the more power you are making, the smaller the gap you will need.

A spark plug's voltage requirement is directly proportionate to the gap size. The larger the gap, the more voltage is needed to bridge the gap. Most experienced tuners know that opening gaps up to present a larger spark to the air/fuel mixture maximizes burn efficiency. It is for this reason that most racers add high power ignition systems. The added power allows them to open the gap yet still provide a strong spark.

With this mind, many think the larger the gap the better. In fact, some aftermarket ignition systems boast that their systems can tolerate gaps that are extreme. Be wary of such claims. In most cases, the largest gap you can run may still be smaller than you think. (NOTE **)




NOTE: * So, with all this information we now know that heat range has a direct reflection on Gap... If we have a plug that the manufacturer recomends a .060" Gap and is the stock heat range, but we decide to be smart and tighten that gap to .045", we are intern affecting the heat range drastically beyond the manufacturers intent for that plug.

NOTE: ** The myth of the larger the gap = more power, is just that, a myth...The manufacturer of the plug recomends a gap for a reason. When you alter the plug, what are we really doing to our engines..? Makes you think twice doesnt it....


4. Indexing

This is for racers only !!

Indexing refers to a process whereby auxiliary washers of varying thickness are placed under the spark plug's shoulder so that when the spark plug is tightened, the gap will point in the desired direction.

However, without running an engine on a dyno, it is impossible to gauge which type of indexing works best in your engine. While most engines like the spark plug's gap open to the intake valve, there are still other combinations that make more power with the gap pointed toward the exhaust valve.

In any case, engines with indexed spark plugs will typically make only a few more horsepower, typically less than 1% of total engine output. For a 500hp engine, you'd be lucky to get 5hp. While there are exceptions, the bottom line is that without a dyno, gauging success will be difficult.

385LT1

Here is a pic of an Autolite 605 , copper core spark plug.

manufacturers recomended gap .060"
Gap after installed for NOS .045"

During the dyno tune the Air / Fuels were way lean.
(Hence the color, bright orange'ish brown)

The tuner got the Air / fuel's down from 14.8-1 to 13.8-1.
This helped a great deal, and stopped the check engine light, "O2 lean condition"..

After NGK TR6's were installed, the light came back at WOT, and sometimes at part throttle. "O2 lean condition".

Since i altered the gap beyone the manufacturers intent. from .060" to .045". I lowered the amount of energy required to arc the spark across the Gap, intern lowering the Tip Temperature. Which would lower the heat range. The plug was already 1 heat range colder at .060".

In this picture, do you see how after tuning the plug was inaffective in buring the extra dense air / fuel mix....?

It didnt have enough spark energy because of its design to totally burn the fuel. because it was altered from stock specs..

So i purchased the NGK TR6 because it is recommend to run a .035" Gap.... and that is exceptable with NOS..

Performance was phenominal...


Autolite 605