Power Gain From Stock 428FE To A 462 cu. Stroker ?

[427HISS]

How much power could you expect from a stock 428FE with a 462 stroker kit and good aluminum heads ?
I know there's many variables, but just a average.
How much more with a great pair of heads ?

[chilly460]

428 --> 462 = 34ci difference. 

A decent street FE is 1.1hp/ci so call it a 37hp gain
A really good streetable FE is 1.4hp/ci so call it a 47.6hp gain

Specific output probably will go down as cubes are added, all things else being equal, but that's a ballpark. 

[427HISS]

"Specific output probably will go down as cubes are added''.

Why does that happen ?

[WerbyFord]

"Specific output probably will go down as cubes are added''.

Why does that happen ?

Even with the best heads, you rarely GAIN HP at the same ratio as your EXISTING HP (eg 1.1 HP/CID).
Really good heads will gain you maybe 0.5 HP/CID as you add CID.
Vanilla Grocery Getter heads on an engine already decked out with carb, intake, headers, cam, you might only gain 0.2 HP/CID as you add CID.

For example, in the old NHRA days (back when heads were stock), NHRA factored the 396 L78 Rat at 425hp. The identical 427 L72 Rat was only factored to 435hp. So NHRA figured 10 more HP for the added 31 CID,  or about 0.30 HP/CID, and those Rat heads were some of the best flowing heads of the 1960s.

Usually TORQUE will scale almost exactly as you add CID since the heads etc arent starving it for air yet.

[chilly460]

"Specific output probably will go down as cubes are added''.

Why does that happen ?

In the case of a 462, you’d be looking at more friction from the increased stroke, more windage losses, and probably the biggest thing is you have more cubes breathing through the same bore size so it’ll cumulatively make a bit less power per cube than the 428.  Any bottleneck in the induction/exhaust will impact the increased displacement a bit more

[427HISS]

So a stock 428FE is better than a 428/462 ?

[chilly460]

A decent street FE is 1.1hp/ci so call it a 37hp gain
A really good streetable FE is 1.4hp/ci so call it a 47.6hp gain

No.  As I said, all else being equal, you could reasonably expect 30-45hp more going to a 462. 

[My427stang]

I would look at the decision a different way

If a 428 and 462 were built in a similar way

- New crank cost is a wash, but if you don't use a new crank, it's not really the same quality, plus you need machine work, magnafluxing etc.  Balancing is a bit more money with the 4.25 arm, but it's not much more if you internal balance both

- Rods are cheaper for the 462, much better selection, and have a better bearing diameter and generally lighter.

- Pistons, if you go with an equal piston and ring set are a wash on price, but the 462 is significantly lighter where it counts

So, assuming the same level of quality you get 30-45 HP (and lb ft) for equal or less money. 

Now if you are going to compare part on hand to a new set of stroker parts, it may not be cost effective, but you'd still end up with more power