308 NGK's BPR6EIX or BPR7EIX

My car ('77 GTB) runs best and fouls plugs less with 6's gapped to 0.030" as opposed to 7's.

https://www.amazon.com/gp/product/B07SBHQR56/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

 

What kind of car? Its kind of important.

 

Have you ever considered the correct gap? It works better.

 

Mine's a 308 carb same as yours - switching to one grade hotter made a big difference for me (from 7 to 6).

 

Brian, what gap do you recommend? I have tried 027 and 030 and it runs better at 030.

 

Have you ever looked at the label under the hood or the owners manual? Its much smaller and with stock ignition I have never seen one run well with bigger gaps not to mention more fouling. Doing it the factory way is typically better and for good reasons.

 

Thanks Brian.

I have Pertronix ignition with Flame Thrower coils and no ballast resistors. I always thought and have been told that with the increased spark produced by that setup, it was better to run a larger gap.

I know the workshop manual and the data plate say a .020 gap. Maybe I will try that and see what the result is.

Thanks

 

I guess you ignored what I said in the last post. Oh well.

 

AFAIK, the 308GT4 WSM has a kind of crazy spark plug gap value of 0.4 mm (.016"), and the .02" value on your 1977 US data plate may be truncated/rounded (I don't trust it being only 2 decimal places rather than 3 when expressed in inches). The euro 1975 308GTB OM (and many later carbed 308B/S F OMs) show a spark plug gap value of 0.6-0.7mm (.024"-.028") so might be more of the value that Ferrari eventually "evolved" into for the carbed 308s.

PS I'd vote NGK heat range "6" for rational US street driving. If you are often on the Autobahn or the Autostrada at triple digit MPH -- go with "7". JMO.

 

Brian,

I didn't ignore your post. I understand you are saying it is best with the factory ignition set to factory specs. I said I would try the current ignition setup with the factory gaps and see what happens that's all

We have owned the car since 1978 and have put 180K+ mi. on it. I have done more tune ups on the ignition, carburetors, and engine than I can count. I have also tried all kinds of different ignition setups over the years. The factory R1/R2 points/Microswitch, R1 points only, Mallory optical modules with pinwheels and the last 5 yrs. or so with the Pertronix setup. I have gone back and forth to the factory setup many times during those changes.

I can say that with the current setup, the car's idle, throttle response, and overall performance to redline has never been better! Even better than when we drove it off the Ferrari of Atlanta lot in 1978!

I am a tinkerer and love to try new things. Have been involved in motorsports/engine building my entire life and have built dozens of race cars, drag cars, and high performance boats.

I don't know everything by any stretch of the imagination! But I have learned a little over the years and still to this day constantly ask questions to those with knowledge! I view you as one of those kind of people and always appreciate your input!

Thanks!

 

More gap czn be an issue at high rpm as the coil may not be able to genrate all these "bigger" sparks.

Not an issue with your beefy coil. You may have to change the distributor cap more often though.

If you need stronger spark at idle, I would assume that the car runs slightly lean, or at least leaner than factory spec (probably better in terms of emissions), in this case the hotter plug is indeed better.

 

The recommendation is based on the heat range of the original Champion plugs, that were actually equivalent to an ngk 8.

These plugs were super cold and suited to agressive driving (the sort of driving that was acceptable in Europe in the 70s, but that brings you to jail now...).

Even back then, the NGK8 proved to be a not so good substitute (aside from heat-range, self-cleaning does also matter ), so NGK7 was used. As now we baby the car even more, NGK6 is the way to go.

Thin tip plug can be gapped slightly more as the thin tip allows for a more focused spark (i.e less energy sucked from the coil). The manufacturer does not recommend to gap them, because the tip is fragile, but regardless of what they say on a stock ignition the factory gap is not appropriate (too big).

 

My OEM plug was a Champion N-6Y; these were too cold for everyday driving. I switched to the next hotter plug, Champion N-7Y. My next trial was the Bosch platinum equivalent of the N-7Y: WR6DP which is a resistor plug. The platinum plug was more resistant to fouling. Because I have the stock ignition system, I have always used the factory gap of 0.025”. Overall, the use of a hotter platinum plug reduced low RPM fouling. For Champion plugs, the higher the number the hotter the plug.

 

Carbed was in the text referring to cars of others, not yours.
If you read NGK recommendations they absolutely require gap adjustment. Ferraris heat range recommendations were made assuming European style driving. In the USA we just do not have the long hard, high RPM use seen there. In addition modern plugs have wider heat range capability than when those numbers were published. It has long been accepted in the NGKs that a 6 is a good choice for a carbed street car, a 7 was appropriate for early F.I cars.

Not needing to be gapped is an ill educated wives tale and goes against NGKs own information. Follow Ferraris recommendation on that. I suspect they have better information to determine that than keyboard warriors suggesting otherwise.

 

Brian,

So, the WSM says 0.4mm gap (0.0157 in.) and the data plate says 0.02 in. I gapped a set of NGK BPR6EIX's to 0.020 in. and put about 80 mi. on it today. Car ran great (same) as before with a set gapped to 0.030 in. I will be putting another 200 mi. or so on the car tomorrow. Will pull the plugs Sunday and read them compared to the 0.030 ones.

Thanks,

Greg

 

I experimented with all kinds of plugs in my 1977 GTB and definitely found better results using hotter plugs. Especially with regular street driving I found the colder plugs to foul too easily. As such I run NGK BP5ES plugs. They are a non resistor plug and one heat range hotter. I did play with EIX iridium plugs but just did not see an advantage with them at many times the money.

 

Brian,

You were absolutely right! Plug gapped at 0.020 is hotter and cleaner than at 0.030!
Below is a picture of both. 0.030 on the left, 0.020 on the right. I have my carb tuning a little on the rich side as it runs better, more consistent that way so that shows on the plugs. But you can definitely see the hotter strap and overall cleaner plug at 0.020.

Thanks again for your input Brian!

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