Help with my new to me KB 2.1 cobra

colinmitchell111

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Looking for some advice from some 96-98 KB 2.1 owners. I bought the car modded and the previous owner bought it that way as well and didn't know too much detail. I know it has a forged bottom end, 2" pulley, JLT intake, stock manifolds, no cats, 39lb injectors, boost a pump, boost a spark, 3.73 gears. Came with a walbro pump but not installed so I'm assuming stock fuel pump. Also has a snow meth injection kit installed and hooked up but not turned on. I've only ripped on it a few times because it's making a lot of boost and I'm not sure if this is right. Here's a 3rd gear pull on a cool dry day. Is the boost supposed to creep this high? The Dyno sheet that came with the car it was only making 9-10 psi but from the date that was before the built bottom end and not sure about the meth. Any advice would be appreciated.

 

wirelessguy2005

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I havent seen too many of the 2.1 kb's make that much boost on a 96-98 cobra setup. Mine makes 12 lbs but I modified the inlet to get it there. Just a heads up but I would pay real close attention to your fuel pressure, it was dropping off the higher you went in the rpms and that can spell disaster even with a forged bottom end. If it's boost referenced it should gain a pound of fuel pressure for every pound of boost so your fuel pressure gauge should have been reading somewhere around 55 lbs if it truly is making 15 lbs of boost . I took the boost a Pump off my car when I upgraded to the walbro 465lph pump. My 97 cobra is rock solid at 51 lbs fuel pressure for the entire run.
 
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me32

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Id get it on a dyno. Hook up another mechanical gauge.
 

wirelessguy2005

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It's possible that the gauge is giving a bad reading or that the vacuum line supplied to the gauge is sharing a vacuum line with something else which could cause the gauge to read incorrectly.
 

wirelessguy2005

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Installed the pump and a canton high flow fuel filter. I am running e85 so that setup may be a little overkill for you unless you want to switch to e85. I left the factory fuel regulator in place and haven't had any trouble.

Did you just upgrade the pump and that's it? Or do you have a full fuel system with a adjustable fuel pressure regulator?
 

venom1997

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Also the stock manifolds will net you higher boost numbers if you put longtunes expect a few psi drop


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