Bronco 302 to 351....!

[89Bronco58]

Ok i have an 89 ford bronco with an AOD automatic overdrive tranny and it had a efi 302...the 302 took a crap and i had an efi 351 laying around....the motors in and all bolted up..but a few problems are...i dont kno where the egr goes to, i kno the egr valve itself bolts to the intake but i dont kno where the pipe or whatever that comes off the bottom of it goes.....???anyone?...second is that ive been told that i have to change my computer...is this tru and what if i try and start it with the 302 cpu in there, what will happen?....third is are 302 and 351 efi fuel injectors the same????? fourth is that on the passenger side behind the head theres a plug that comes off the wiring harness that goes nowhere, i dunno if it plugged somewhere on the 302 or not...anyone? anyone help me please!!!!!!!!

 

[BLADE262US]

Well first the EGR tube on a 351 goes directly down to the passenger side exhaust manifold and on a 302 it went back to the back of the heads where it connected to sort of a manifold that connects between the 2 heads so if your goona use it you have to figure out how to hook it into the passenger exhaust pipe or find a 351 passenger manifold , I would not run it without atleast plugging that tube because the EGR opens at highway speeds to allow spent exhaust gasses back in to be burnt again lowering combustion temps and lowering emmisions . If its open to atmosphere it will allow extra oxygen into the chamber and have directly the opposite effect possibly burning pistons , Second yes you have to change the computer it will start and run but wont perform worth a shit and will more than likely cause damage to the pistons . The system on most of these trucks is speed density and its preprogrammed in the computer the ammount of fuel it needs to squirt per stroke volume along with timing curves now a 302 has a 4 inch bore and a 3 inch stroke so you take 3.14 X rX2X stroke it gives you 37.68 cubic inches per cylinder X 8 = 301.44 ( 302) Then you get into how much fuel to squirt to acheive 14.7 to 1 parts air to parts fuel you see where the volume of the cylinder is important . A 351 is 3.14XrX2X stroke( 3.5 on a 351 ) and you come up with 43.96 cubic inches per cylinder X 8 = 351.68 . So theres 6.28 cubic inches different air volume per cylinder goint from a 302 to a 351 . Now your 302 computer is pre programmed for that 37.68 and is going to fire the injectors as such to acheive 14.7 to 1 air fuel it doesnt know you have added 6.26 cubic inches of air to the equation so it is going to end up very lean .Wow long winded this morning arent I . The fuel injectors are the same as long as the plastic part of the body is the same color they are color coded I dont remember right off but I think the stock ones are 19 lb per hr more than enough to support a mildy modified motor . And finally the plug you are refering too would have plugged into the top of the block between the heads in the back of the motor to a knock sensor that I think they only used in the 302,s if the motor spark knocked from like bad gas or an extreme load the EEC would ****** the timing so many degrees to correct it the 351,s dont use it . One other thing I hope you didnt use the 302 flywheel on that 351 because it will have a vibration youll never get rid of they are weighted different I think the 351 is a 28 oz and the 302 is a 50 oz . Hope that helps ya out /emoticons/[email protected] 2x" width="20" height="20" />