spark plugs
 

i went to an auto parts store to get spark plugs and they didn't have the number i needed so they cross referenced it and they had autolite 3924, will those work for the car or no?

Welcome to the forums. Have you seen this parts breakdown on Mazdatrix? I would recommend a high quality plug like NGK instead of the Autolite just because it's available locally.

http://mazdatrix.com/ign-2.htm

With Amazon Prime or RockAuto, you could have whatever you need nearly just as fast.

we haven't had any luck with ngk plugs at all, plus i got a gift card to that specific store to help get the car going

If its an auto parts store and can't order NGK plugs, they are not an auto part store, IMO

there were ngk spark plugs, but whenever we got them they blew out within a week, we don't trust them, we've had nothing but trouble, so we went to get autolites and they didn't have the number i needed, so they cross referenced and was wondering if the ones i got would work

Another recommendation for obtaining and installing the correct NGK plug that was designed for the rotary engine you have. Not certain what you mean by the plugs blew out,they're well made and reliable.. maybe some problem the car has is fouling them out,were they wet with gas or oil when you removed them,does the engine produce smoke while running?

I do not have any experience with Autolite plugs except for our Ford vans.
I was having ignition issues awhile back. Plugs kept fouling. Turned out I had intermittent igniters. Plenty of gas, but not always a spark.

Compare the images.
The Autolite has 1 electrode whereas the NGK's specified for my 84 12a engine, have 4. Also the profile is different.

I personally not use any plug not specified. Just a bad feeling.

Since we're comparing pictures - one of these rotors wasn't getting correct ignition due to bypass of oil through the oil control rings on the intake side;
https://oi61.tinypic.com/2iw8sbd.jpg

If the OP can pull the exhaust manifold off and take a look there, it might tell us more about what he means by plugs 'blowing out' - because that's certainly not the norm with the proper NGK plugs which our cars REQUIRE.

Single electrode plugs will not maintain the duty cycle required of a rotary-engine specific plug, and will be toast in short order...

I used autolites when I was sorting things out after dropping in a rebuilt engine. The electrodes were getting shorter and shorter within days. Eventually, they would've failed.

I've had NKG's that had lasted years and years. They are worth the extra cost, and hassle of special order.

the Autolite 3924 will not work.

firstly, its not the correct cross, 3924 is the miata/protege/every piston car on the planet spark plug, the rotary uses a different plug. NGK 2329 or Autolite 2526.

the NGK is the best plug choice for a stock car.

the autolite has its uses, but the gap it comes with is HUGE, and the stock ignition will burn itself out trying to jump it. the gaps are also inconsistent. and since the autolite only has 1 electrode when it should have 4, it wears much faster.

this does change if you have an MSD or some other ignition amplifier, then the autolite is a valid option.

NGKs last an ass-ton of a long time. I'm the second owner of my rx7, and the original owner kept a "Ship's Log" of all he did to the car - last spark plug change was back in '92, and I just had to replace them two weeks ago. Guess what were in the engine?

NGKs.

Guess what I put back into the engine?

New NGKs.

Those things seem like they last a damn long time, perhaps you've been getting some bad luck with them. I ordered off eBay from a good seller, dropped em in and the car ran like cherry.. give NGK another chance :) (Besides, it seems to be the most recommended choice!)

We aren't trashing Autolites here, but NGK and Denso were the OE spark plugs for our cars depending on the year meaning Mazda took the time with these companies to design a spark plug specfically for our cars. If you had one set of bad NGK plugs that is fine, but NGK is normally a really good plug and very sought after. Even a lot of American muscle guys use NGK plugs.

However for the RX7, I have had good luck with the NGK plugs. I have been getting about 15k miles out of them easily. My friend tends to take my 15k mile plugs, clean them and then use them for another 10k or so before they start showing sings of misfire. I have a set of Bosch plugs made for our cars many years ago that worked fine also.

If you go buy plugs from Mazda for any of their cars, they will give you NGK plugs unless told otherwise. Most performance Honda and Mazda owners swear by NGK here in the US. Denso is also great, but doesn't have near as good as a presence.

On top of that, almost every single RX7 owner on this board uses NGK plugs. Why? Because they work.

Now for your issue, what do you mean your spark plugs were blown out? And was it in the Rx7 or another car?

I prefer to run Autolites in my 69 GMC pickup, but in my Rx-7, its NGK all day, every day. I replace my truck plugs every year or two as well, where my rotary ones, almost never.

GM=AC delco
Ford= Motorcraft
Dodge= should have glow plugs
VW&Porsche= Bosch
Jap anything = should have the rising sun on the box NGK

Dodge used to be champion, idk about new ones

Run nothing but NGK or Denso plugs on your engine. This is an absolute MUST!! If your NGK plugs failed within days then you either have fuel or ignition issues or low compression causing fouling of the plugs. No plug on the market is as good as an NGK plug for our 7's. I love the NGK's so much that I used them in both of my Corvettes, and I'm currently using them in my BMW. It runs amazing with the laser iridium plugs in there! You should replace your plugs once every two years in the 7 to maintain optimal spark.

Welcome to the forum. I agree with everyone else here. I have seen the autolite plug that "fits" the RX7. It does have the same thread and lenght, but that is it. It is an entirely different plug with a different purpose. The parts counter man is correct, that the crossover claims this plug will work, so don't blame him.

NGK or Denso is what you want. If they don't stand up, you need to look elsewhere for the issue. PS if you foul a brand new plug, it can be cleaned, if done very carefully. SO you don't need to throw out a plug after it failed a test. Some auto parts stores ( the full service type that have attached automotive machine shop) will clean them for free ( or at least they did some years ago!)

Make sure your fuel is fresh, as it turns bad after sitting. If your fuel is over 6 months old, it is suspect. Drain tank, put in a fresh 5 gallons or so, and give it a try.

If you post up exactly what is going wrong ( details are important and pix) there are enough people here that can help you make it run well.

Good luck in getting it running properly

Rich