pandorafowler

do i need to change out the mechanical fuel pump for a in-tank pump or can i just keep the mechanical

NJ SPEEDER

if your mechanical pump is capable of being regulated to at least 10psi you can prolly get away with it on a stock motor. either way you will have to install a fuel return line since tbi uses a bypass type fuel pressure regulator.
an in tank pump is not a difficult conversion. you can get a pick up/fuel level sender assembly from a junk yard car and jsut adapt it in. when you grab teh stuff, just be sure to grab teh wiring harness for the pump too, that will save you a lot of time.

later
tim

pandorafowler

luckily my wrecked 88 has the in-tank pump. the reason im asking is because my 86 z28 has the quadrajunk and i was looking into replacing it with the tbi from the 88. a damn idle mixture screw snapped in the lower plate of the qjunk and i`ve heard of people getting better results after swapping to the tbi. I replaced the stock intake with a performer and it has a aftermarket cam in it (dont know by who, first owner put it in). with those little mods, would the tbi do better than the qjet or about the same?

JPrevost

About the same. The job of the computer system is to do 2 simple things. Control fuel and timing. The TBI is probably going to be more accurate at controlling fuel delivery, especially in light throttle daily driven instances, so gas milage yes. But both have very wimpy spark tables which is probably more of a difference than the fuel delivery. So if it's power you're after, it's a toss up. Depending on which way the wind blows you might see 4 or 5 hp, heck, just a few degrees difference in coolant temp could set off some freak knock with either system making you think it's inferior when in reality it didn't have a chance to do it's job. There is one major problem with the way guys go about tuning their EFI cars these days and it's timing. As far as I'm concerned, fuel delivery is defined into 2 catagories, computer controlled and no-computer controlled. If it's got a computer, more than likely the fuel is going to be right on (unless SD and not compensated). Then there is timing, who in their right mind would setup a carb dizzy without knowing max timing? When you tuned you had to figure out the springs, the weights, the vacuum advance, base, and total. It erks me that people in general think all computer controlled vehicles have the same timing and so comparing one EFI to another EFI should be solely based on fuel delivery . This is the only reason I play with TBI like I do. I feel very strongly that if a carb can make the power that a dry-flow system can, then why can't a computer controlled carb do the same if not better? Wow, sorry for going off on a tangent, I do this often after spending hours in the machine shop.