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1183 Views 7 Replies 5 Participants Last post by  8psiSi
Ok, if you've followed the 8psi milled head post here is an update. I got everything installed and now there is a problem at high rpm....from about 5500 rpm up. It starts bucking a popping out the exhaust, kind of like hitting the rev limiter but less extreme. I also can see black smoke coming out the exhaust. It seems like the ignition is cutting out. The air/fuel ratio guage stays in the rich, I adjusted the SAFC richer and leaner and made no difference. I believe it is an ignition problem, but I have a Crane capacitive discharge ignition, LX91 coil, MSD distributor cap, brand new NGK plugs (1 step colder), and Nology wires. The ignition has been on the car for 6 years, I'm wondering if the coil is getting tired? The only fuel related thing changed was the fuel pump, I installed the 255lph pump supplied with the Jackson boost upgrade kit (had a Walbro 190lph in before). I'm going to try and gap the plugs a little closer and see what happens? Any other ideas? Remember my compression ratio is approx. 10 to 1.....and I'm very confident it is not running lean. I've got a steady 75 psi of fuel pressure and also have the 310cc injectors. I'm open for suggestions.
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Black smoke? Since you mentioned milled head, the only thing I can think of is that they either didn't mill it properly or they installed the head gasket incorrectly. The black smoke sounds like you're burning oil in the cylinders...
I've had the same cylinder head on the car for about 15K miles and I personally installed the headgasket (D16Z6 metal one) myself with ARP head studs. The motor does not burn oil. Hey man I thought you were a know it all, black smoke is fuel, blue smoke is oil. I'm dissapointed. :(
u could just be running super rich now with the upgraded pump u got in there. when i went to dyno for my turbo, at the high rpm like after 5.5k it'll start popping too like backfire with black smoke...i had 280cc injectors and a 12:1 fmu at the time so i was super rich like 8:1 i think.

so it could be too rich. but thats all i got...sorry

What kind of Air/Fuel meter? What is the boost doing at this point when it starts popping? I have read that a lean idle will have slight popping to it. My car idles at 22psi and stock injectors and it will pop very lightly when warming up. Are you still running water injection, is that system boost dependent? Just some questions?
It's running 35 psi fuel pressure at idle. Runs about 75 under full boost. The boost guage stays steady at 8psi. It's an autometer air/fuel ratio guage. I have played with the SAFC settings, leaned it out and richened it up in the high rpm and no difference. I am hearing a lot of bad things about the Nology spark plug wires so I'm going to swap those out and see what happens. Up until 5500 rpm it feels really strong now. I'll be having it dynoed within the next month or so probably.
Well I figured it was the Nology spark plug wires. I swapped then out for some stock wires and she pulls hard all the way to redline. The car feels much stronger now with the 8psi, I'm anxious to get her on the dyno now.
good shit hope you come back with some get #s
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