to burn the fuel though you need airflow, to get airflow you need a shortblock to pump it, and the necessary work on the induction system (head, cam, manifold, carb) to support the requirements.

 

So the first question you need to ask is what will the rules allow for speed groundspeed and engine speed.  How much of an engine do you wish to run and at what speed, 226 inches at 1700 RPM, 400 ar 2000 RPM, or 300 at 5000 RPM, each is going to require a different setup.  The second question is what can be done to support what you wish to do.

 

A bored and stroked shortblock is useless if you have a poor induction system.

 

I've got a set of rods and sleves, pistons to make good power with minimal work and money if you wish.  But it's nothing compared to the power you can make if you open up the checkbook.

 

So, get decent compression in the engine, stock at 7.5 or 8 to 1, there's pretty good gains made when raising it.  Then head work, manifold work and carb swap/modifications will help. 

 

A WD used a taller piston to make up for the difference in stroke from the 4" to 4.5" stroke crankshafts.  Putting them in the longer stroke engine required a little machine work. 

 

I did do a fair bit of work on the head, manifold and carb though.  I had a cam ground and then changed the cam timeing to what I wanted. 

 

for example a stock Allis D17 or Gleaner E head will flow around 120 CFM in stock form and the maximum valve lift is just over .400 where it does it.  A stock manifold of D17 type will flow about 114 CFM.  With the carb neck bored out and the radiuses flared back above it, it will flow better, the amount depends on how extensive the work is.  The next choke point is the radius where it bends to go twards the head.  If one does enough work, a "stock appearing" manifold will not choke the head at any point.

 

With some proper work on the cylinder head the airflow can increase quite a high percentage.  For example at lower to mid lifts it can be near doubled from stock.  Maybe the maximum isn't doubled but the total amount available to the engine throughout the valve cycle is increased a verry high percentage.

 

But it's going to come down to the carb, what it is and how well it's matched to what you need.

 

If you are looking at doing it cheap, there's some lesser priced ways to get engine displacement, but none of it is cheap. You really need to decide how much work and money you wish to invest.  It may end up being a simple rod and piston swap to get some compression, maybe an offset grind on the crank with a rod swap, or a full blown build that will end up being several thousand dollars. 

 

It only costs the difference, parts are parts and don't go part way once if you want to go all the way in the end, it just ends up costing more doing some things twice.