4k gsk nowhere near 4000rpm - Diesel Bombers



12 Valve 2nd Gen Dodge Cummins 94-98 Discussion of 12 Valve 5.9 Liter Dodge Cummins Diesels with P7100 Injection Pumps

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Old 06-10-2017, 08:44 PM
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Default 4k gsk nowhere near 4000rpm

Hello, i recently installed pacbrake 4k gsk in a 96 cummins that i swapped into a 97 gmc dually and i can maybe get 2800rpm. That is even with the springs tightened down a bit more than spec. Engine idle is about 150rpm higher but still starts as good as before. I have a steady 35psi fuel pressure at wot from an electric lift. Any ideas as to why rpm is so low? i measured timing the other day and it was approx 11deg by the measurement charts i had found, from what im told stock is 12, would this have an effect on higher rpm to this extent? any advice would be great, thanks!
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Old 06-14-2017, 05:28 PM
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I'd say your doing pretty good if you can hit 2800 at 11, I've seen trucks that will barely run at 10. I'm not saying that's your problem, but I suggest you bump it to at least 15-17 and see what happens. Do you have stronger valve springs? Because you'll float your valves if you spin it anywhere near 4K with stock ones.
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Old 06-14-2017, 05:34 PM
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I do not have stiffer springs yet but am aware and would be staying away 3300ish plus for the time being.. just seemed that 2800 was a bit low. Illadjust my timing and seen what its like after that. Thanks for the feedback.
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Old 06-15-2017, 04:47 AM
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Good luck
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