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porscha356

spark plug for rebello built L "2150" B motor

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Good Day all,

 

I have been experimenting with spark plugs.......  The car is a 510 with a Rebello 2150cc. street motor.  It has twin Mikuni 44's for breathing.

 

Dave sent me home with ngk b6es.  They worked but were pretty dark upon later examination.  He then recommended B7ES and these were better but still not optimal.....light brown around the tip and just a bit over the top of the insulator but dark at the bottom of the insulator well.

 

Car then had some sorting of the carbs, which was done by Dave Prima of Concord, a former Mikuni  rep for many years.  Dave P worked a bit of magic and the car ran great.  Recently, it has started backfiring through the carbs and being hesitant on takeoff after sitting for 4 months.

 

SO, I decided to change the plugs again. Just for grins as I didn't have the correct set for the next colder plug, I temporarily put in some ngk bpr5ea-L-11 from my old 1991 Isuzu Trooper I had lying around, just to see if it started and ran.  Much to my surprise the car ran so well I took it for a test drive on back country roads and the difference was amazing.... all the popping and hesitation disappeared.  It performed very, very well.

 

I pulled the plugs after a drive of about 18-20 miles to check the color and there was absolutely no carbon fouling at all.  But there was no light brown color either.  In fact, the plugs seemed clean, but then maybe it didn't have a chance to color up on so short a drive.

 

So, fellow travelers, does anyone have any suggestions for me on how to proceed?  Plug type and heat range?  Warnings?  Advice? Opinions?  Let me know.

 

Thanks to the membership.

 

Bob

 

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What ignition are you running?  Not knowing , the bpr5ea-L-11 (BP5RES-11) are cool gapped at .040" ish

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First world Datsun problems.

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If carbon fouling I don't know why he would go from a 6 to a colder 7 as this would mean even less self cleaning of the plug. Going to a 5 was the sensible thing, assuming the air fuel mix was OK.

 

 

NGK plugs are hotter with higher numbers.

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Dead white is too lean, or too hot of a plug.

Call us back when you burn a hole through the piston.

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Is it too clean, whitish? That's too lean, careful.

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20 miles is not a long enough drive to see how the plugs are truely burning.  Put a set of new plugs in and drive it a while.  Becarefull if it is to lean you will burn something.  It sounds like in the beginning the carbs needing adjusting as it was burning rich and you inititially tried to correct the richness with changing plug heat range.  Start at square 1 with the plug heat range.  Too lean will ping!  Too rich will smell rich.  Uses your senses also.

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Hey Bob. I worked for Dave Rebello for many years and if there's one thing I can say, it's take his advice.

 

If you're still having problems, they can help you sort them out. They have their engine dyno, but also are now doing roller dyno tuning. Since the L4 is not rocket science, they can probably get you tuned without either dyno. As long as your carbs and distributor are set up properly.

 

Did you buy the motor from them?

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They do run a bit smoother with projected tip plugs, but can possibly ping more as well. I've gone to the extreme (ngk race plugs that are 11 heat range). Good nitrous plug but light throttle cruising or putting they foul up. I'm going to have a "street set" of plugs and "track day" ones this year.

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I have been experimenting with spark plugs... He then recommended B7ES

Non-rebello, webers running rich.

Have bp7es on the shelf.

Had a set of platinums from somewhere and they were good, for ~500 mi.

Have bp5es in there now. I like them better for daily driving, being stuck in traffic.

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PUT IT ON A DYNO! 

 

I would say call Dave Prima and ask if he knows of a place he could meet you at. Might cost less than one of Daves "street" engines. 

 

 NOT an engine I would willy nilly down the road till you KNOW she's dialed. 

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NGKs are COLDER with higher numbers!!!!

 

6 would be stock compression

7's are best in 10:1 area

11:1 8's

We run 12's in our 14:1 motor.  

 

If you call NGK with engine build details including compression, carbs, displacement, etc... they will recommend you likely use one of their race plugs (non-resistor) given the extreme build.  The call is free.  

1-877-473-6767

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Yeah I caught that the next day. They are opposite most other makers.

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That's what happens when u try to b different it causes confusion

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