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73-87 Chevy _ GMC Trucks => Performance => Topic started by: LTZ C20 on October 05, 2014, 09:13:23 pm
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Hey all, I'm experimenting with which spark plugs I want to use in my mild performance street engine. I've used the stock AC Delco plugs, AC Delco rapid fires, I currently have the Accel Shorty Header plugs in.
My buddy has the E3 plugs with 3 electrodes and the baseball diamond shaped plate, he said they run great and he has a Comp cams top end kit with an intake and holley carb.
My engine is a 355 with Dart aluminum hi flow heads, oversized int. and exh. valves, comp cam, edelbrock dual plane performer rpm intake, GM Performance HEI, Hedman headers, true duals and a throttle body fuel injection kit.
What's your guys opinions, preferences, recommendations?
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Assuming 14mm X 0.750" reach, projected tip, gasket seat, 5/8" hex, and minor clearance issues with headers - Champion 3071 Platinum regapped to 0.045" or Champion RC9YC5 (alternate #426) copper core gapped to 0.050" or Autolite 3924 copper core gapped to 0.045".
Currently running the RC9YC5 in a 355, 10.0:1, zero deck, 0.039" quench, forged/forged/H-beam, AFR 195 centerbolt (2.05" x 1.6" x 65cc), Comp XFI 0.560" lift roller, Crane 1.6 Gold Race rockers, MSD distributor & wires, Crane HI-6/LX92 CD ignition, and TBI w/Edelbrock MPFI conversion.
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That sounds pretty good. Thanks. What octane are you running? How's the fuel milage?
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Runs 93. Mileage is atrocious at ~11 MPG around town with 3.42s and 31x10.5-15.
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I'm sure your tires aren't helping any. I have 265/75R16, running 91 octane and 4.10s. I'm not sure what my exact is but I do know my old motor with same tires and a th350 was suckling down 3/4 tank in like 3 days. Now I can go a week, sometimes 7-8 days on 1/2 tank, that's with a new 700R4 to.
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Also, what would be the best position for the j strap to "face" or "point" inside the combustion chamber. I believe it's called "indexing"??
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Have been doing a lot of research about indexing of spark plugs. Very interesting practice for sure! Not so necessary for street use but very useful on the strip.
A new question to ponder is, do I use the stock AC Delco R44TS plugs or the AC Delco 41-803 plugs for a 89-90 5.7L TBI truck. I ask this because I have a TBI kit on the truck from that model year, bought kit from Howell Engine Developments. Very good product!!!
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For the Dart aluminum heads? Dart indicates 14mm x 0.750" reach flat-gasket spark plugs for their performance aluminum heads. Which heads by part number did you install?
The Delco R44TS is a 0.460" reach tapered seat plug. For factory heads use Delco R43CTS, Autolite 24 or Accel 0574S shorties if headers limit accessibility.
Don't use a 0.460" reach plug in a 0.750" reach hole or you'll shroud the spark.
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Yes for the dart aluminum heads. I installed the biggest and baddest of course lol. Part number 127322.
I thought those 2 AC Delco plugs would be ok because, 1 - the heads have stock style plug location, 2 - R44TS is the stock plug for my truck, 3 - if the heads have stock plug ports, I should be able to put the stock plugs in. Also, I see there is a small tapered area at the top of the hole so I thought tapered plugs would be ok. So having almost shot myself in the foot, I now need to figure out what AC Delco plug is a 14 mm hex gasketed .750 reach plug and if possible one that if ment for a TBI engine.
Sorry for my blunder as I am still learning, not an expert yet lol. That's why I ask you guys!
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Using summits search filters, I found this.
An AC Delco, 14mm, .750 reach, gasket type plug. AC part number 41-106, GM part number 12610767.
Will this plug be good for these heads?
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You should have received important reference pages with the heads, similar to those attached, below.
I recommend you put together a binder to organize and keep all important information and details regarding your build for future reference.
Seems like you're predisposed to AC Delco plugs. Use a manufacturer's cross-reference to find plugs similar to those I posted for you earlier.
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Yes I have 2 of those papers, 1 came with each head. I have all of my engine build papers in a zip lock bag labeled "ENGINE". For example though, the exhaust gaskets recommended are a Fel Pro with part number. It says what dimensions of plug to use just not a part number which erks me a little because I know for sure I saw an Accel part number somewhere on the paper work for those heads. Been all over and can't find it, if I had the Accel number I was gonna cross it to AC Delco and be done.
I am predisposed to AC Delco yes, but I work in a Chevy service department so parts are close and easy and if there's ever a problem easy to get replacements.
Your recommendations crossed to ACD numbers.
Champion 3071 platinum - ACD 5
" RC9YC5 - no ACD equivalent
Autolite 3924 - ACD FR1LS, FR3LS, FR5LS, FR3CLS, 5, CFR3CLS, FR2LS, FR3LSK, 41-629, 41-603 & 41-611
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I spent some time googling the specs for the large list of plugs. Most of them are pretty close in dimmensions, some i couldn't find all of the dimmensions for. The biggest factor is the varying heat ranges.
I want a plug that is the proper dimmensions for the heads, and has the best heat range for a TBI engine with aluminum heads.
The ACD number i posted earlier that also has the 8 digit number fits all specs but is a 12 on heat scale i believe.
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Every manufacturer has their own proprietary heat range scale that relates strictly to their offerings. Heat range assignments do not directly relate between manufacturers. Bear in mind that "4" in Delco does not correspond to "4" in Autolite, Champion, NGK, Bosch, etc. Each has a unique numbering system. And, finding an accurate chart that cross-references heat range between specific manufacturers can prove frustrating. Nonetheless, an Internet search will usually provide what you're after.
With some manufacturers, the heat range of their plugs relate directly to the spark plug part numbers. For instance, an AC Delco R44TS runs hotter than an R42T; a Champion RC12YC runs hotter than an RC9YC. With other manufacturers, NGK and Denso for example, the heat range of the plug increases inversely with part number - that is, decreasing spark plug number relates to increasing heat range.
Then of course, some manufacturers produce a narrower selection of plugs than others, so you encounter one part number of Brand X crossing to half-a-dozen part numbers of Brand Y. So, keep "plugging" away and you'll find what you're after. ;)
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Ok let me ask you this then. What would the best heat range be for a TBI engine with aluminum heads running 91 octane gas. Should I use the heat range for the year of the truck or the heat range for the TBI or does it not matter at all. This all of course will be an AC Delco plug so we shall stick with there heat range scale.
The plug I mentioned earlier, part number 41-106 or 12610767 meets all physical dimmensions and spec for the cylinder head but is I believe a heat 12.
The R44TS, obviously is heat 4. Is 12 ok for TBI and aluminum or is that too hot and need to down around 4-6?
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Aluminum heads transfer heat more rapidly than iron so better tolerate high compression w/o detonation. But, installing a plug that is too hot can introduce preignition. Choosing a performance plug is, in part, a matter of selecting heat range and electrode style so that the plug cools effectively w/o fouling while being hot enough to not introduce preignition over a broad temperature range. An extended tip plug is a good choice for street use, because the electrodes are cooled by the influx of fuel and air while locating the spark kernel deeper into the combustion chamber. However, selecting heat range is partly a matter of experimentation.
The Delco 41-106 is used predominantly in four-bangers.
Delco 19308030 (#5 RapidFire Platinum) is used in late 80's, early 90's Vettes and should work in your engine as a reasonable starting point. You can always go up or down in heat range as you dial it in.
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Ok the delco 19308030 you provided sounds good. I put a set of rapid fires in my old engine and they didn't seem to work very well. BUT, that was an old iron 350 that was carb and I eventually found it was eating oil pretty bad. I possibly also got a cold plug, maybe 3 or 4. So, has anyone else had problems with rapidfires? One of the guys at work hates them lol. I got no problem using them as long as I know it was just my situation and not the plugs that was bad. I would prob get a 5 or 6 if I use those rapidfires.
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Kevin, don't misconstrue the information I've posted. I don't "recommend" Rapidfire; it's just that you insist on Delco. You could just as easily use a conventional 41-602 (5614285). In my dealership experience Rapidfire is just another platinum spark plug. They work no better and no worse than any other Delco plugs. The biggest problem with Rapidfire is the number of offerings. It's sort of a one size fits all, meaning that Delco attempts to cover too many applications with too few part numbers. They're certainly no miracle - the mystique of Rapidfire amounts to advertising hype and sales! Clever way to move a product. But, then, that same approach is used by all spark plug manufacturers. There's only so much to be accomplished by a spark plug - its actual purpose is limited and very specific. Conversely, referring to claims that all "choose the brand" spark plugs are junk is ridiculous (although one exception does come to mind - ::)). Ignore the hype!
The "secret" to choosing the right spark plug is to settle on the one that works "best" in the engine. If the plug is selected accordingly, it will yield respectable service. If not, it may well tank - and in some cases result in engine damage. It's a matter of finding the right fit. So, pick a starting point (brand, type, heat range). Regarding Delco, I would stay within the heat range of 3 - 5. With any manufacturer, a cooler plug will be less prone to preignition. Then experiment if you're not satisfied. Try various brands, gap styles and heat ranges, until you find "the plug" that functions the best in "your" engine, while providing suitable service life at an acceptable cost. You will likely find several that work, a few that simply won't, and one or two that shine. I used Champion, NGK and Bosch, in various gap styles, electrode material and heat ranges before settling on the Champion RC9YC5. In another engine, even of similar build, the optimum plug might be hotter, or a different electrode material, or a different gap. Brand loyalty should be the very lowest of your concerns. Choose the plug that works the best!
One other caution I should mention: The extended tip style plug I previously recommended may interfere with some domed pistons, because of the electrodes' protrusion into the combustion chamber. As long as you are running flat top or dished pistons this will be of no concern. But, if you have installed domed pistons, then spark plug-to-piston clearance should be checked along with valve-to-piston clearance.
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That's all I want! Lol I've been unsure where to start with. Should I be looking in the low or hi heat range. If what I've heard about rapidfires is true or not. Now you gave me a starting point, 3-5. You also said Rapidfires do there job in the right application, that reliefs my worry. So now I know if they don't seem up to par, it may not be the plug, it's that plug in my engine, no big deal. What's better or not for aluminum and TBI.
I have dished pistons, I checked when I was assembling the engine and I have good valve clearances, also I've had the plugs out before and they weren't damaged so I'm pretty sure that won't be an issue.
Thank you very much for your help and patience, there is a science behind spark plugs and the more I've been working on this little plug search the more I learn and get confused also haha. I really appreciate all your help.
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You are welcome!
BTW - Be sure to chase the spark plug hole threads before installing the longer reach plugs if you have run the engine, since carbon builds up in the exposed threads of the holes. Additionally, I recommend installing the plugs with oiled threads or a sparing amount of "copper" anti-seize.
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What should I use to chase the threads? Just a 14mm bolt? Specific size and thread pitch?
I always use copper anti sieze.
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Also, what's the heat range on the Champions you use.
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What should I use to chase the threads?
Use a tool designed to chase 14mm x 0.750" reach spark plug threads, such as a Powerhouse Products POW351690 (http://www.summitracing.com/parts/pow-pow351690?seid=srese1&gclid=CO23vJHopcECFRVufgodCIcA5w) or Lisle 20020 (http://www.summitracing.com/parts/lil-20020), etc. It's a good tool to have in your toolbox. The last choice would be an M14 x 1.25 tap, because you do not want to remove any metal from the head. I would not recommend using anything else to chase spark plug threads in aluminum heads!
Also, what's the heat range on the Champions you use?
Champion 9, which roughly corresponds to an Autolite 3 and an AC Delco 1.
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Ok. I will locate a tool or tap at the local auto parts store or hardware store.
Ok cool. I did I search on summit racing and selected the physical specs for the plugs, I didn't not specify brand so I got choices from alot of brands. I will sit down and make a chart so I can easily identify the best candidates and there availabilty.
On a side note, don't you live here in california?
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Purchase the rethreading tool. Use a tap only as a last resort.
I'm about an hour and a half south of you.
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Oh ok. I'll do my best to find one. In fact one of the guys in the shop at work might have one.
Yea that's what I thought. Not to far at all.
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Hey BD, so I made a chart with a selection of plugs from AC Delco, Autolite, Champion and NGK. All plugs meet the physical specs for the heads. The chart has their part number's, heat range, price and material, including copper, nickel, platinum and iridium. Here is the chart.
(http://tapatalk.imageshack.com/v2/14/10/14/cd25404b03b8891f3f3220d0b6b27c71.jpg)