Daze

Due to a post below “390 or 351? Which would you pick?” I decided to do a little experiment. I fired up digital dyno on my computer and crunched the numbers using the specs for an FE 390 and then increasing the stroke on the 351W out to the identical displacement as the 390 (389.6 cubic inches). I realize there is no stroker kit that makes a 351 completely identical to a 390, but that’s ok I just wanted to compare the theoretical #s for the sake of argument. I used the same configuration on both motors: compression, cam specifications, intake specifications, carb size, valve size, and headers. What I found out is that the torque and HP #s are identical between the 2 motors from 1500 to 3000 RPM after that the 351 stroker begins to fall off and is producing 6% less torque and HP at 5500 RPMs. This makes sense due to the increased stroke. IMHO the 6% difference is compensated for by the 100+ pound difference in weight between these two motors. As far as individuals saying that FE motors are some Mecca of torque producing motors, that can pull stumps and raise the front end off of the ground, It really comes down to gearing. A vast majority of cars that came with a 390 in them came with low gears, 3.50:1 or lower, so of course torque at the rear wheels will be at a premium. If you take an FE390 and put it up against a stroked 351W in identical cars with identical transmissions, rear ends and traction the results will be the same, at least below 3000 RPM, and minimally different above that, if different at all due to the extra weight of the FE.

67mustang302

You also have to consider the cost of parts, head availability, cams are different for the engines etc. You can build a 351/392 as well. Parts are more readily available for a Windsor engine too, and it's easier to fit in a car than a big block. I prefer small blocks for the street myself, you could always build a 5.0 on an aftermarket block and run a crapload of boost with a turbo and blow any big block away, get twice the mileage and have much less weight. Depends on how much you wanna spend

69FECoupe

What were the peak torque numbers for the Windsor vs. the FE?

JMD

I say that if the Mustang already has a 390in it then go with the 390, a 390 swapfor a SBdosent make much sense to me unless someone just happens to have a good 390 just laying around. Even in this case, the conversion cost should be factored inbefore jumping into the middle of such a project.

I wonder how much more moneyDaze's hypothetical "built" 390 would cost in comparison to a similar build for a SBW? 40% or 50% more?

I suspect that thedollar toHP ratio is much less for the SBW.

JBradley500

in an issue of mustang and fords they had a 428fe vs 427w. it was pretty interesting but its pretty hard to keep things even. honestly i dont think the CI's of one was correct either unless there was a mistype...it also makes me cringe when it says 8L not 7L.

http://www.mustangandfords.com/techa...est/index.html

67mustang302

Small blocks are cheaper to build, unless you talk hard core race, when you need to go to a pricey aftermarket block(Dart, World, Ford etc). Big blocks are much sturdier at the insane power levels of some drag racing when compared to a small block.

andrewmp6

i wouldnt use a fe unless i stroked it as far as i could and cobra jet heads on it.

fastbackford351

One of the beauties of the FE was that it was a full floating setup made to run on the red-line all day long. NASCAR teams used them for about 15 years with great success.

FE= Farking Expensive

Norm Peterson

I think it's more directly related to the bore size. Since I doubt that valve placement in the combustion chamber is considered in the digital dyno,the larger bore of the 390 offers slightly less shrouding and hence better breathing with the same valve sizes. Stroke ends up being whatever is necessary to equalize the displacements, although the longer stroke engine probably experiences a slightly greater amount of friction HP loss.

Just for grins, what does the digital dyno predict ifyou make the 390 intake & exhaust valves each 0.025" larger for approximately the same shrouding as in the 351 stroker?


Norm

my77stang

i saw one person touch on the fact that the FE's are built like brick sh*thouses..... you can safely run SO much more power without fear of essploding anything. not to mention shaft mount rockers which are more stable without needing rocker girdles or a jesel setup ($$$$$$$). plus a larger bore is ALWAYS better. sure they are heavier, but they are wicked motors not to mention having one is becoming something of a rarity whereas EVERYONE has a SBF