Bore and Stroke considerations--Is HP the only measure

[Slohand42]

I'm researching and planning my 1/2 VW build.  Have three different plans to compare.  My question is, has anyone considered  the question of bore and stroke combinations not only for HP but for torque?

I'm an old hot rodder and biker.  I've rebuilt a number of engines, and have owned and driven multiple cars and bikes.  What I do know is, the longer the stroke, compared to the bore, the higher the torque in a gas engine.  The HD V-Twin has always been a serious torque monster, being able to pull hard from low rpms.  It's stroke is much longer than it's bore.  You can't rev the stock motor high, but can pull a mountain at low rpms. 

The small block V8 motors were designed with strokes shorter than the bore, making them high revvers attaining their HP numbers at higher rpms, but not a ton of torque.  One of the favorite hot rodded versions of the small block Chevy is the 383.  It gives the basic 350 a longer stroke, thus giving it higher torque.  This translates into a great street engine making its useable power at the lower rpms of street use.

The Continental A65 has a bore and stroke that is closer to equal producing its hp at 2900 rpms.

Due to this, I would think that the longest stroke possible (86 mm) and maybe with a smaller bore, say maybe a 92 would produce a torquier engine making it's useable power at a lower rpm, thus allowing a longer or possibly a more aggressive prop.

Something to chew on.

What do you think?

 

[Chuck in Indiana]

I'm researching and planning my 1/2 VW build.  Have three different plans to compare.  My question is, has anyone considered  the question of bore and stroke combinations not only for HP but for torque?

I'm an old hot rodder and biker.  I've rebuilt a number of engines, and have owned and driven multiple cars and bikes.  What I do know is, the longer the stroke, compared to the bore, the higher the torque in a gas engine.  The HD V-Twin has always been a serious torque monster, being able to pull hard from low rpms.  It's stroke is much longer than it's bore.  You can't rev the stock motor high, but can pull a mountain at low rpms. 

The small block V8 motors were designed with strokes shorter than the bore, making them high revvers attaining their HP numbers at higher rpms, but not a ton of torque.  One of the favorite hot rodded versions of the small block Chevy is the 383.  It gives the basic 350 a longer stroke, thus giving it higher torque.  This translates into a great street engine making its useable power at the lower rpms of street use.

The Continental A65 has a bore and stroke that is closer to equal producing its hp at 2900 rpms.

Due to this, I would think that the longest stroke possible (86 mm) and maybe with a smaller bore, say maybe a 92 would produce a torquier engine making it's useable power at a lower rpm, thus allowing a longer or possibly a more aggressive prop.

Something to chew on.

What do you think?

I once had a 39 Chevy business coupe street rod with a 350/350 cam, etc. It "sounded" bitchin.. but was a much better street engine when I built a 383 for it. 
So, yes.. I'd go for the long stroke engine.
That said, I've been running an 1835cc VW in Mouser for uhh 42 years now. It gets the job done, but at higher rpm. You need to fly in ground effect until 90 to let the prop unload and rpm to come up on takeoff.