my 1988 F250 351w/c6 auto has over 150,000 miles on it and the motor needs a rebuild. i thought while i was at it i would put a stroker crank in it (we haul horses and have camper so could use more torque). My plan was to build a 393 that would have at least 300hp. i don't need to go too radical as this is a daily driver and farm truck. My question is will i have to convert to mass-air or can i get around this with different injectors, regulator and a custom chip? The mass-air conversion from speed density may be just too expensive/complicated. I have read some posts that claim mass-air is not necessary so now i am unsure.
thanks for your help.

cheers,

Rusty

 

I would think you'd have to switch to Mass Air, because Speed Density won't know how to compensate for the extra 42 cubic inches you'll be adding.Even if you used box stock EFI351 heads&a stock(or mild)camshaft in it(393cid) the Speed Density system would be confused,and it would most likely tend to run lean and/or have idle problems.If you did a build-up with a stock boreXstroke 351,or even with it .030, you shouldn't have a problem sticking with Speed Density.A computer-compatible cam,a set of headers,a "chip",and some exhaust upgrades should get a EFI351 around 300 horsepower, with a decent amount of torque for pulling heavy loads. Good luck with your project.

 

>my 1988 F250 351w/c6 auto has over 150,000 miles on it and
>the motor needs a rebuild. i thought while i was at it i
>would put a stroker crank in it (we haul horses and have
>camper so could use more torque).

Which transmission do you have??
It makes a lot of difference...

>My plan was to build a 393
>that would have at least 300hp. i don't need to go too
>radical as this is a daily driver and farm truck. My
>question is will i have to convert to mass-air or can i get
>around this with different injectors, regulator and a custom
>chip?

It's a toss up, mass air is tunable, just by unhooking
the battery, letting it sit for an hour, then reconnecting,
it'll "learn" all on it's own...

>The mass-air conversion from speed density may be just
>too expensive/complicated. I have read some posts that claim
>mass-air is not necessary so now i am unsure.
>thanks for your help.

Some really high tech injection systems still use MAP
systems, MoTec comes to mind, but are you really competant
with tuning fuel maps from out of thin air?? I have some
experience doing this, and it's very time consuming, and
expensive if you're using a dyno...

I don't know how much a custom tuned chip is going
for these days, but the MAF system would probably be
a cheaper source for the torque you're looking for...

Either that, or convert to a carb...

Steve & the Rockette
'63 F100
'68 F100
'72 Capri 2L
'73 Capri 2.6L V6
'73 MG B GT 2.6L V6(Ford)
'98 Contour SVT 2.5L V6 (Mods)
'01 ZX2 (No Mods yet)

 

i have the C-6 3 spd auto tranny. So i guess what you guys are saying is to convert to mass-air, stroke it, get headers a new cam and maybe a chip? Do you think porting the stock heads will be good enough with this rebuild. And what about the intake. From what i gather i will need a donor vehicle with a standard transmission for the mass-air conversion. correct?

thanks for your help.

 

Donor vehicle?? Heck no, Ford Motorsport sells
a conversion kit...
Part # M-9000-T50...note; Call the Tech "Hot Line"
for 5.8L modification instructions...$675.00 but
thats last years catalog...

Steve & the Rockette
'63 F100
'68 F100
'72 Capri 2L
'73 Capri 2.6L V6
'73 MG B GT 2.6L V6(Ford)
'98 Contour SVT 2.5L V6 (Mods)
'01 ZX2 (No Mods yet)

 

Besides the Mass Air conversion kit available through F.R.P.P.,if you are set on the stroker 351,they offer a complete 392 cid 351 with a serpentine water pump(part # M-6007-A392)that produces 430 bhp@5,500rpm & 450 ft./lbs. of torque@4,000rpm for $6,250.The M-6009-A392 short block lists at $2,995.Compression ratio for both is 9.7:1.You'll have to use your EFI351's top end,but the complete 392 comes with GT-40 aluminum cylinder heads.The short block is the cheaper route to take,but you'll have to re-use a lot of the parts currently on your 351.I wouldn't put stock EFI351 heads on a 392-inch Windsor.If you opt on the short block assembly, add big valve,aluminum heads to it,so it will breathe.That said,ported stock,iron heads,fitted with larger valves will work,but weigh more than aluminum heads.It all comes down to thisower costs $$$$,how fast do ya wanna go???I'd call F.R.P.P.'s techline to get more info.

 

Thanks for the input guys. I presume you are talking in U.S. dollars and that is a big problem for me. The Canadian dollar is at about $0.62 which makes that mass-air conversion kit $1100.00 and that crate motor $10,000! I bought the whole truck for $8900 CAN. So i was hoping to save some money by finding a donor vehicle for the mass-air conversion. With regard to heads, i think the cost vs. weight thing limits me to iron. that said is there any heads you can recommend that would be sufficient with the stroker crank that i can pick-up cheap and maybe do some porting work? Also i am not sure what you are talking about with the short block vs. long block thing. I need torque and reliability for hauling and daily driving.
again thanks.

Rusty,