5.0L to 5.8L in 91 f150 4x4

C.W · #1 (**permalink**) 01-23-2009, 03:02 AM

I know its a common topic.......................
My 91 f150 4x4 has a tired (310000kms) with the E4OD and bw1356 t-case (manual t-case if it matters)
Its time for a swap, I have a good running 351w low milage rebuild but its an earlier carbed one. I think i now have all the brackets and intake for the efi conversion on it.
Im wondering if the older one will produce the same power as a true efi 351 or is it lacking due to cyl head and cam technology at the time?
Also do i definately need to swap computers?
If so does it have to be from a 351 E4OD combo to run the trans and does 4wd make a difference?

Any info is greatly appreciated, Thanks.

Conanski · #2 (**permalink**) 01-23-2009, 09:03 AM

Is your truck mass air? If so you don't need a 351 computer and you probably don't need to worry about the cam.. though if it's a stock grind cam the motor will benefit greatly from an upgrade.

C.W · #3 (**permalink**) 01-23-2009, 12:46 PM

It is not mass air.

Conanski · #4 (**permalink**) 01-23-2009, 01:43 PM

Then you will need a 5.8/E4OD computer and you'll have to make sure the cam is an SD EFI friendly grind, doesn't have to be a stock cam, just one with at least 114deg LSA and relatively short intake duration(under 215deg@0.050"). The cams in my sig qualify as do the stock F4TE grind and the 5.0HO cam as well.

C.W · #5 (**permalink**) 01-23-2009, 07:50 PM

Ok. thanks.

Why does the 5.0L computer not work?
Is it the firing order difference?
I was told the 5.0ho works fine so i dont understand the difference with swapping a 351 in. Is there something else different?

EPNCSU2006 · #6 (**permalink**) 01-24-2009, 05:49 AM

The additional 49 cubic inches is the primary reason. For equal manifold pressures on a 302 and a 351, the 351 requires more fuel. This additional amount of fuel is likely outside the adjustment range of a speed density 302 computer. A speed density 351 computer will plug right in to a speed density 302 wiring harness, so it isn't anything major to swap.

Conanski · #7 (**permalink**) 01-24-2009, 10:50 AM

There is a firing order difference between the motors but that doesn't matter on the SD system because the injectors are fired in groups of 4 and they are wired in the same groups for both engines. A 5.8 would run on a 5.0 computer but it would have issues on cold start and when the system is operating open loop(accelerating), because the computer tables are bases on 5 liters of displacement. Over time the computer will learn what it takes to run the 5.8 in closed loop so it will operate more smoothly as time passes, but it may run out of adjustment range at some points in the maps and that could lead to detonation problems and codes that won't go away.

C.W · #8 (**permalink**) 01-24-2009, 05:14 PM

This is all very helpful info. Thanks guys.
This is the first time i have spent this much time on my own ford. i am normally a GM guy but i bought this as a daily driver that i could run trails with and now its gotten way beyond what i had intended, mainly because it has taken all the abuse i have thrown at it over the last 10 months. All my other 4x4's were breaking with less abuse.
So i want to keep this one going, but for some reason im having a hell of a time finding the proper computer for this swap around here.
Thats why i was hoping it would run with the 302 cpu.

loudfords · #9 (**permalink**) 01-26-2009, 12:16 PM

Quote:

Originally Posted by Conanski

but it would have issues on cold start ... detonation problems ....

I ran an 88 351 in my 87 F150 on a 302 computer for a long time. Never had any cold start problems. Never had any issues with lean or detonation either. It ran rich, if anything. I think the 351 had bigger injectors than the 302?

Conanski · #10 (**permalink**) 01-26-2009, 12:39 PM

Quote:

Originally Posted by loudfords

I ran an 88 351 in my 87 F150 on a 302 computer for a long time.

Yes I believe that, especially if the motor was stock. Both use the same 19lb(orange) injectors BTW.

C.W · #11 (**permalink**) 01-26-2009, 12:41 PM

So if i am just putting a stock 351w in i should be ok?

My 351w was originally a carbed motor that i got the efi stuff for if it makes a difference.

Conanski · #12 (**permalink**) 01-26-2009, 04:40 PM

Stock means it has a stock EFI camshaft or one that is very close, the typical cam installed in a carb motor is not EFI friendly.

pud · #13 (**permalink**) 01-28-2009, 08:47 AM

Penticton! come join the BC chapter CW. Im from Kelowna origionally (ok well winfield, errr lake country), hows the weather down there?

Kemicalburns · #14 (**permalink**) 01-28-2009, 07:37 PM

also be sure to get a 5.8/e4od flexplate. do not install the 302 flexplate on that 5.8 motor.

Loudfords, your system ran rich because the 302 computer was trying to compensate for the added cubes.

also know that your 302 Y pipe will not match up to the manifolds on the 5.8. the 5.8 is wider. finding a y pipe for the setup you plan to run shouldnt be hard at a wrecking yard.

C.W · #15 (**permalink**) 01-28-2009, 09:50 PM

Quote:

Originally Posted by Kemicalburns

also be sure to get a 5.8/e4od flexplate. do not install the 302 flexplate on that 5.8 motor.

Loudfords, your system ran rich because the 302 computer was trying to compensate for the added cubes.

also know that your 302 Y pipe will not match up to the manifolds on the 5.8. the 5.8 is wider. finding a y pipe for the setup you plan to run shouldnt be hard at a wrecking yard.

Will the 5.8/c6 flexplate work on the e4od?
Are they balanced different?
Im aware of the exhaust issue, was gonna run duals.