Here's a typical plug in my engine. It was starting to have a low speed intermittent miss that cleared up with RPM. These were NGK R5671A-9. I have no idea why I bought those. They look a little rich and probably a lot cold. I just bought a set of Champion RC12YC that Edelbrock recommends for their heads. What does anyone else run in an Edelbrock head and have good luck with? 9.5:1 compression, TA212 cam, headers, Q-Jet that might need to be leaned out.
NGK FR-5 https://www.rockauto.com/en/parts/ngk,7373,spark+plug,7212 https://www.rockauto.com/en/moreinfo.php?pk=33348&jsn=263
The NGK R5671A-9 is a recessed electrode race type plug. I would never run a plug like that in a street driven vehicle. The FR-5 is a projected nose plug and offers a lot of advantages for street cars. The Champion plug is very similar. NGK plugs have plated threads, great for aluminum heads, no anti seize necessary. Edelbrock heads use the same plugs as TA heads, flat seat, 3/4" reach.
How I arrived at that plug, is unknown. They ran OK for 4 full years until this season when they started having a low speed misfire. I think a hotter ignition/MSD probably masked many issues. I'll take the Champions back and get the better NGKs.
There is only minor difference in the 7373 vrs 7173 is the 7373 is a heat range 5 with a 5k resistor. The 7173 is a heat range 8......colder in ngk terms.....and a 1k resistor. The gap on 7373 is .008 larger from the factory..... 039 vrs 031
When you get the right extended nose plug in the motor you will likely find that atleast at large throttle openings you will need less timing and your idle might clear up some also!
Yup Up to 11-1 compression I use the FR-5 (NGK Stk number 7373) 12-14-1 gets the R5672A-8 plug (7173) Boosted motors will get an this 8 or possibly the 9 heat range version. Plugs for our motors are pretty simple Lower compression iron heads.. up to 9.5 to 1.. Use NGK UR 4 or 5 (6630 or 2771) Higher compression Iron heads-- NGK UR6 (7773) Alum heads NA applications below 11-1 FR-5 (7373) Alum head 12-14-1 gets the R5672A-8 plug (7173) Alum head Boosted motors will get the R5672A-8 or 9 or even the 10, depending on what is going on.. (7173, 7405, 7942).
You may have trouble finding them in your local parts stores. Rock Auto has the best price on them I believe. 1.55/plug. Edit, I just looked and most sources want double that. Jegs was the next cheapest at 2.49. https://www.rockauto.com/en/parts/ngk,7373,spark+plug,7212
Time delay is the problem. A good deal next week doesn't beat driving it today. I can get them for $25 at O'Reillys.
Yup, 3.00 + per plug is what I am seeing. If you like them, stock up at RA. I think you will see a big difference in the way the engine runs.
That plating works fine, once. How is it the second, third, fourth time you pull the plugs out? I like anti-seize.
The only time I pull them out is to change them. Anti seize is fine as long as you don't pile it on to the point it interferes with heat transfer. https://ngksparkplugs.com/en/resources/5-things-you-should-know-about-spark-plugs Not sure about repeated removal install of the same plugs. Might be a question for NGK.
Who the plugs out 4 times? When I worked for an OEM that used NGK/Nippondenso plugs from the factory, we were instructed to NOT put anti-seize on the new ones, during major services. There was a long technical internal training video done on the causes of plug seizure, and on how any compound on the plugs inhibits heat transfer, thus making seizure more likely. unless your taking them out ever other week, just to make sure they still have an electrode on them... The rest of us might have a plug in a hot rod street motor, that is used lightly, for years, if not decades.. Cars like this spend more time sitting, than driving. JW
Installed and started after 2 pumps. All is good with the world... Now, if I could just get my 350 machining done.
