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I found the perfect L28ET spark plug


jgkurz

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I have run the NGK BP8ES at 20 psi for years with no problems. The projected nose is worth about 4 deg adv compared to non-proj. Total adv is 28 deg with 8:1 CR in L28.

 

I don't know what your setup looks like, but on 92 octane premium my engine would ping holes in the pistons at 28 degrees and 20 psi. Have you done some special work to your combustion chambers?

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Yeah, lots of chamber work unshrouding valves and polish with Cratex. Removed 3.5 cc ea chamber. Cam is old Racer Brown turbo grind 246°I/236°E at 0.050" with 0.485 lift on N42 head and block. MSD TurboTimingMaster retards 18° init to 28° final at 20 psi. Aria's forged pistons with reverse deflector dish vol of 11cc and 11:1 A/F on boost. I/C is 160 sq in unit first import of HKS back in '87. Turbo is Turbonetics H3. I probably should't admit it, but been at this since '75 and blew a lot of motors along the learning curve.

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I guess we are all masochists who love a challenge. Persistence hell, its obsession.

 

Sure got a lot of laughs from that link. Good to know I'm not alone. Kind of sick sense of humor, but I really roared. You really know how to wield Maxwells Hammer. I just kind of sneeked up on it.

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Went out last night for some testing. I regapped to 35 and the car runs better when cold and fine once warmed up. Boost is set at 15.5 psi and no pinging at all. I haven't tried the -11's yet. I had to add a bit more fuel because at low 14's and high 13 afr's the car misses a bit.

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Guest bastaad525

Wow... learn something new every day. I didn't know projected tip plugs give you 4 degrees more worth of advance....

 

So wouldn't you lose some power going to non projected tip plugs? I wouldn't be able to recover from 4 degrees worth of retard... my stock '81 CAS setup only allows me to advance to roughly about 22*.

 

Anyways, I'm kinda confused now... which NGK's were the ones used from the factory? It's BPR6ES -11 right? I'm running BPR6EY -11's right now and I do get a bit of misfire at idle, decided not to care about it anymore :)

 

I really don't want to go with the non projected tips and lose 4*, and I run the -11's because I'm running MSD 6A and gap at .050" (no this didn't cause my idle misfiring... even when I tried .030" I still get this misfire).

 

Also, what's the difference between the BPR6ES and the BPR6EY's?

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Guest bastaad525

Why is .050 too large with MSD? .044 is stock gap, I believe, we're only talking about a .006 increase. I get no misfiring on boost (even during several dyno pulls), and the misfire at idle didn't go away even at .030 gap. I'm not 100% sure, but I seem to remember the MSD install instructions mentioning that you could open up the gap a bit from stock when running it, .005 or .010 increase recommended I believe. I know the car feels better to the butt dyno with the larger gap.

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You often can increase the gap size with a MSD unit. However, the factory 0.038-0.044 gap is already on the large side. Many experts feel that about 0.045 is mas size for gap and large spark.

Also as boost is increased from stock, gap needs to be made smaller, the MSD can counter that by keeping the gap at about the same range as factory with slightler higher boost. So with a 0.05 gap you most likely will not get better spark and instead will get some misfire under boost. I run my car at 15psi and keep the gap at 0.038 with a msd unit.

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Guest bastaad525

*shrug* I'm running 14psi now, and get on it up to 6000rpm at every chance I get, and have not once felt the slightest miss. I mean... you would feel or hear it if it was there yes? Or is it being masked by the higher rpm? Would it be noticeable on a dyno graph?

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well if the misfire is slight , you won't necessarily feel it. It could also be that you have no misfire, the point is that at 0.050 you are more likely to have misfire than better spark. Off course every set up is a little different, so if you feel it works better at 0.050 in your car you can jusst keep it there

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