Northern 7

iTrader: (3)

OK - I don't want to get burnt to a crisp on this post so hear me out before I get the "DO A SEARCH!!"

I want to change my plugs this weekend and I'm hearing and reading lots of advice on going to the 2nd or 3rd gen plugs (on this site and others). Believe me, I searched, and the popular opinion is "all over the place". I hear 1st gen, 2nd gen, 3rd gen - I'm also hearing platinum, leading, trailing, and at least a dozen different NGK stock numbers. In a nutshell - I'm confused as hell!! Can someone please provide me with info on the most durable plug (and best performing) plug for a 1st gen with MSD (and RB header/exhaust) and I don't want the the 1st gen stock plug - what would really make it easy is if someone can provide the NGK stock number (ya know - spooooon feed me - I'm an idiot!!)

A quick resonse and I will be eternally grateful

Thanx - Northern 7

MIKE-P-28

iTrader: (1)

A common misconception of many people are the terms "Hot" spark plug, and "Cold" spark plug. The temperature rating of the plug refers to the running temperature of the physical spark plug - i.e. a "Hot" plug will retain more of the combustion heat in the plug itself, meaning not transfer the heat to the engine itself. This is why a "Hot" plug is needed for slower city type driving so the carbon deposits will be burned off the plug, and clean firing will still be possible even when combustion temps are low (idling, stop & go etc.). At the same time a "Hot" plug used in a highly modified engine that is driven hard consistently (racing) will simply retain too much of the extra combustion temperature and burn itself up (usually cracking the porcelain, and potentially doing major engine damage).


A spark plug that is too "Cold" for the engine/application will start harder, foul much easier, and generally be a pain to work with.

For engines that are not significantly modified for racing, we have had very good luck just running the stock plugs. For street ported engines driven hard on the street, the most we have had to do is move one or two heat ranges colder. This lack of change is because the engine is still driven at normal speeds and loads for 99% of the time.


Racing engines, for the most part, are above 7000rpm 100% of the time - these are the ones that require the colder plugs. Quite often a set of "hotter" plugs must be used to get the engine started and warmed-up, because the race plugs will not fire consistently below 4000rpm.

Spark plug choice, for any given engine, can then be stated as "Hot" enough to fire consistently at the lowest RPM and load normally needed (without fouling), and not overheat (and burn-up) at the highest RPM/load for the given application. This translates to : The "Hotter" the engine (modifications, load, usage, etc.) the "Colder" the spark plug needed.

MIKE-P-28

iTrader: (1)

Heres your normal spark plug @

81-85 (12A) Both L/T BR8EQ-14

Northern 7

iTrader: (3)

OK Mike-P-28, I hear you - but what's all the talk/raves about guys going with the 2nd/3rd gen plugs in their FB?? Word is they last longer and perform better - is this a misconception? I just want to have the best plug possible in my car - and since they're ready for a change, I thought it would be a good time to ask the question. If I read you right, you're saying I don't need anything other than the stock NKG - Am I right?
BTW, nice write up - appreciate the info - sounds like I need a hot plug

MIKE-P-28

iTrader: (1)

Stockers is all I ever used in a 12A, but looking at a 2nd gen plug looks likes it would be tougher. But I really dont know on using them in a 1st gen. Its been talked about a few times in here, dont remember the general concenus on the subject tho..

jeremy

iTrader: (1)

i was curious about this too.

etherhuffer

Go to Paul Yaw's page and read his stuff on plugs. It will tell you a lot more. I think plugs are over rated. If you have clean plugs and an MSD, you can't get too much better for the street.

smnc

My 2ng gen plugs DO last longer and and seem to make the car start a little easier... But then again, the starting thing could just be fact that the plugs were new...

I'm trying the 3rd gen plugs next time (same as the 2nd gen, but platinum)

The 2nd gen plugs are: BUR7EQ-14 trailing and BUR9EQ-14 leading (I think... that might be backwards)
They don't cost me any extra and last longer so... works for me...

Northern 7

iTrader: (3)

thanx smnc - that's what I was looking for.

FJ

I just replaced mine with 2nd gen plugs this week. As I had no need to change the heat range I bought 4 trailing plugs, BUR9EQ. The 13B came with 9's. If you have a 12A, they use 8 I believe, one step hotter. I imagine you could find BUR8EQ's if you did not want to use a colder plug.

Without trying a new set of each, one after the other, it would be hard to see a difference but they definitely appear to be more durable. I've not heard of anyone who has tried them say they did not last longer.

-John.

smnc

I forgot to mention, the 3rd gen plugs have the same part number as the 2nd gens, but with a P in them for 'Platinum"

BUR7EQP-14, etc...

smnc

No prob... Glad to help

SPLzero

what is the gap size for a first gen 12a?

thanks

MIKE-P-28

iTrader: (1)

You dont gap them, they are pre gapped

V8kilr

well since paul yaw said that converting to a side fire plug is better then the stock plugs i will have top say that the 2nd and 3rd gen plugs would be worse as far as performance goes,

one of the reason paul yaw say's to switch is because you can get a hotter cleaner spark from a single electrode as to four,
or something to that effect.

the only advantage i could see with 2nd and 3rd gen plugs is they probably last longer and run a little stronger,
as in they could probably handle more boost if you were thinking of turbo charging.

which is one of the reasons mazda uses those types of plugs on the 2nd and 3rd gen's because they can fire better under extreme pressures

thats why i always laugh when i see those setups at the local auto parts place with the spark plug and when you press the button it sparks, "i think it was for a bosche platinum +4"

thats means nothing to me becuase the plugs act totally diferent under compression

jeremy

iTrader: (1)

i thought all rotary plugs side fired????

smnc

BR8EQ-14
-------^^
That's the bit of the part # that indicates the gap (1.4mm or .055" in case you really wanna know)

smnc

I believe Paul Yaw meant the side-fire conversion more for race cars where spark plug life is not as much a concern as street cars. Yes, it'll give you better spark, but I think most of us want good persormance with a plug we won't have to change every other week.

FJ

[And I would have to disagree.

People have been using 2nd Gen plugs in 1st Gen's for years with good results.
But there is NO question of them hurting performance. They don't. The majority of 2nd Gen's are not turbo, so your point about compression pressures is not relevant.
Chances are, if a four electrode plug was worthless in the rotary, we would have heard about it in the last 20 years.
"the only advantage i could see with 2nd and 3rd gen plugs is they probably last longer and run a little stronger,...
Exactly...

You defer to Yaw a lot, which isn't necessarily a bad thing, but not usually helpful for most people here. He is talking about racing applications for the most part. Not what most people are looking for.

Regarding the single electrode spark plugs: did you notice he was talking about a Bridgeport engine? Did you notice he said the Autolite single electrode plugs don't work well without an MSD? And have you noticed that since he mentioned he found side fire plugs were better and was going to give us an update, it's been over a year with no update?
Basing your opinion on that information alone does a disservice to those who ask for advice with near-stock engines. Even with intake and exhaust and a street port, there is no reason that 2nd Gen plugs are not as good or better than stock.

My point is, you say the 2nd Gen plugs "would be worse", based upon what you read at Yaw's site: That's nonsense. There's nothing to support that. Certainly not for stock engines, which is not what he is referring to, and yet most questions here are aimed at.

Case in point: Yaw's page also says the mechanical timing advance is 20*, for the 12A and the 13B. Not true. This came up in a thread a while back where I mentioned the advance is no where near 20* stock for an -SE or a 12A and a few members had 20* distributors. I've since had a friendly Mazda Rotary mechanic send the factory advance numbers for everything from '79 to '85 and none are 20* advance.
No doubt 20* advance distributors are common, but that is why you set the timing at 4k rpm :it doesn't matter what the advance is. By 4K it's advanced as far as it's going to get.

For most people, chances are they have the stock distributor, hence the confusion from reading Yaw's page. Again, this is misleading for most people who set the timing at idle, with a stock distributor and check it at 4000 rpm to see the advance. Distributors with 20* advance are not uncommon, but that is not what most people have.

Yaw is not talking about stock so using his info is not what the average FB owner needs.
I could type in the stock timing advance numbers from '79 to '85 if anybody is interested.

As far as plugs go, I prefer the 2nd Gen BUR9EQ plugs.

Just my thoughts...

-John.