351w injectors?
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Senior User
Joined: Jan 2004
Posts: 166
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From: Wisconsin
351w injectors?
i have a 351w with gt40p heads 2.02 intake 1.94 exhaust valve and a .450 lift cam not sure of duration but anyway my injectors are junk that are in it and i can get a deal on som 30lb injectors and im not sure if there gonna be to big or not? any input would help alot
FTE Legend
Joined: Jun 2006
Posts: 31,930
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From: Ottawa, Ontario
Too big I'd say, but it depends upon the intake you're using as well. You also need a mass air meter calibrated to those injectors, or a custom chip burned to tell the computer they're not stock.
Moderator
Joined: Jun 2003
Posts: 3,550
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From: Calhoun GA
For a street application, there really is no reason to go with 30's unless it's boosted or sprayed. If this is a mass air application, the air meter will be to be cal'd for a the application and a chip to change the transfer function and injector values.
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Senior User
Joined: Jan 2004
Posts: 166
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From: Wisconsin
its non MAF with a stock intake, if i put my .550 cam back in it will that help or will the injectors still be too big, what will the engine act like if i use these injectors and not reprogram/chip the ecu? also what would you rec. using for a chip if i do in fact need it?
Moderator
Joined: Jun 2003
Posts: 3,550
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From: Calhoun GA
Going off what you have listed in your sig, the stock (size) injectors should be fine. You could actually get away with using an adjustable fuel pressure regulator (FPR) to help dial in the fuel a little better with an aftermarket cam and heads. Tuning changes are needed so the ECU can work with larger injectors, and there's only a handful of companies that can make programs for speed density applications.
Lead Driver
Joined: Nov 2002
Posts: 9,557
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From: Concord, NC
If you use larger injectors without reprogramming the computer, the engine will run way too rich. The computer adjusts fuel supplied to the engine by varying the amount of time the injector stays on (pulse width) and is calibrated for the original size injectors. So at a certain point in the fuel table, the computer will open the injectors say, 10 ms (milliseconds), no matter what injector is physically installed. A higher flow injector will inject much more fuel than the computer thinks it is calling for and will run very rich. Sure there is some closed loop adaptation using feedback from the O2 sensor, but the trim can't go nearly as far as it would need to go to run 30 lb/hr injectors at the proper air/fuel ratios.
