Pirate 4x4 banner

302 to 351 Swap

19K views 41 replies 19 participants last post by  zachis4wheeling 
#1 ·
I have an 89 fullsize bronco with a EFI 302. The motor punked out so i bought a salvaged 351 EFI from a 96 F150. I put my 302 harness on the 351 and bought a 351 distributer that plugs into my harness and put it all in and it all works. It is extremely underpowered though, it won't really accelerate fast at all, I have to get all the way into the gas to get it to do anything. I am just wondeing if anyone might have any suggestions or if anyone has had this same problem. Any help will be greatly appreciated.
 
#2 ·
doesnt the 351 have mass air? and yours does not?
 
#3 ·
and are you running a 302 ecu? more info man...
 
#4 ·
the 89 computer is what is running this motor, the only things from the 96 are the block, heads, oil pan and valve covers, intake & exhaust manifolds, plentum, fuel rail, injectors, and throttle body. everything else is 89 302 stuff except the distributer which is 89 351
 
#5 ·
so basically its a 89 351 with a 302 ecu? hmm... id shoot towards ecu.
 
#6 ·
so i should look for an 89 351 ecu and put it in and see how it does?
 
#7 ·
thats what id start with. that way you have the full factory 351 shit in your truck. no questions. the computer is tuning for a motor that is missing 50 cubic inches.
 
#8 ·
WOW i didnt know you could change everything over like that. I will be keeping an eye on this post to see what you have to do to get it to run right sense i want to do the same thing soon. I thought the intake was diffrent on the 5.0 from the 5.8's sense the 5.8's are a little wider.
 
#10 ·
and? he swapped the distributor, i hope he figured that out. considering the motor was a used motor it probably had wires on it...
 
#12 ·
what pistions were swapped again? i dont remember off hand. isnt it like 3 and 7? i forget...:shaking:
 
#13 · (Edited)
1-5-4-2-6-3-7-8 302

1-3-7-2-6-5-4-8 351


:eek: how bout them fuel injectors?


considering the ecm controls the fuel injectors... id swap the 302 ecm out for the 351. right now, its firing the first order for the fuel injectors, when it needs to fire the second.
 
#18 ·
The 89 computer is batch fire, the firing order shouldn't matter one bit.
It should run OK, but not perfect with the 302 comp. What condition are your cats in? You're symptoms almost sound like plugged cats to me...
 
#19 ·
no cats at all, true dual 2 1/2" pipes from manifolds with glasspacks, no clogs. i switched the "3 and 5" and the "7 and 4" injector plugs like sj suggested but noticed no increase in performance. something just isnt right with this, when in park i can give it gas and it will rev up to 4 grand but sounds weak. when in gear i can put my foot on the brake and dive into the gas with my other foot and the motor will not peak 2 grand, it wont even spin the 35's over in gravel with 4.11's.
 
#31 ·
when in gear i can put my foot on the brake and dive into the gas with my other foot and the motor will not peak 2 grand, it wont even spin the 35's over in gravel with 4.11's.
Its called your converter is reaching its stall speed (normal for stock) and you aren't going to prove anything by doing that except burning your tranny up.
 
#20 ·
timing? or that ecu. id shoot for ecu and then go from there. that way its all factory. who knows what the ecu is tuned for...
 
#23 · (Edited)
The injector firing order doesn't matter at all. They are non-sequntial firing, so leave the injectors and harness alone.

Also -the ECU's rarely go bad.

Are you running the same size injectors, MAF sensor and throttle body?
 
#25 ·
ok, first, forgive me for being ignorant, but i first posed my question on this forum to learn so i will continue to ask more... batch firing? non-sequntial firing?

second, i am using the 351 injectors and the 302 & 351 throttle bodys are the same, i am using the 302 one though

third, so you really think just having this tranny bolted up is causing the motor to be this weak, im tellin you, my old motor was tired but this thing is rediculous, i can barely hear my exhaust, and it used to be loud

i am just completely dumbfounded over the whole thing
 
#26 ·
Non-Sequential firing= The fuel injectors are not set to fire in a particular order as with the ignition. Some people will tell you to re-wire your injector harness to match your ignition firing order. Don't screw with it- it doesn't make any difference- I have done it both ways plus Ford Motor Racing will tell you not to worry about it either.

I would also suggest you double check your wiring.

I experienced a similar problem with my 302 swap and it turned out to be one of the wires off the TFI module was wired wrong. The TFI module has two 12V wires off it. One is 12V constant, and the other should go to 12V ignition only circuit. If the ignition only wire is connected to a 12V constant source, that could also be causing your problem.
 
#27 ·
but he has a factory harness. it shouldnt have any wires wrong... right? and i didnt say the ECU failed. I said it was tuned for a 302. check timing, and wiring...

isnt the 96 a roller cam?
 
#28 ·
first - you put in a engine with 50 more cubes - on a speed density fuel system - it can not make up for 50 cubes -
i agree the wiring on the injectors does not need to be changes as only the mas air motors are multi port - the speed density system is bank on bank - ( even / odd firing order ) not per cylinder as in mas air -
you can check your timing, and fuel pressure, but i say get a computer for a 351 -

oh and my 95, 5.8, mass air, e40d, 33s and 4.10ls - but will bearly brake loose on pavement - the speed density trucks are worse - my old 89 bronco 5.8 -c6 -31 - 3.55 - could slip one tire if you really tried :flipoff2:
 
#32 ·
oh and my 95, 5.8, mass air, e40d, 33s and 4.10ls - but will bearly brake loose on pavement - the speed density trucks are worse - my old 89 bronco 5.8 -c6 -31 - 3.55 - could slip one tire if you really tried :flipoff2:
The problem there is the sponge between the motor and the t-case. My 94 with a 302, m5od and 3:73's would melt my 35's right off the rims.

Now with the np435 and 4:11's I can burn the 39.5's off too. Its definantly got more issues than SD
 
#29 ·
but i had a 5.8 89 bronco speed density that would melt 33s....:D fix the known problem then go from there. the ecu.
 
#30 ·
Diddo on the speed density bs, the sp density can barely make up for a mild cam swap, let alone an increase in displacement. switch to mass air (you have a c6 or aod correct, cause if its otherwise you're kinda hooped) and the sky's the limit because you should have the roller block which something people pay a lot of money for.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top