Torque vs HP

[Bayrunner]

Old School 6 guys were looking for low end torque rather than high end HP to get the 6 down the road, Quick. Theory was that you cannot out HP the larger motors so beat them down low.

New school is always talking about HP numbers. Although, you increase 1, you get some of the other. Is it better to concentrate on torque down low rather than top rev HP in an inline?

Please share your thoughts and experience with a new guy like me. I have lots to leran.

Thanks

 

[rbohm]

8) when building any engine, whether you concentrate on building horse power or torque, depends on what you are doing with the engine. a street engine you want to concentrate on building torque. if you are building a race engine, that also depends. if you are looking for top speeds, then build horse power, if you are on a long straight road course with big sweeping turns, build horse power, if you are on a short straight tight turn road course build torque. for 1/8 mile drag racing or circle track racing build torque. for 1/4 mile drag racing build horse power. for a 1/4-5/8 mile circle track build more towards torque production, for longer circle track up to 1.5 miles build more towards horse power, and for longer trackws build horse power. there are exceptions to the above rules, and you can fudge a bit either way, but follow these rules and you will usually be quite successful.

 

[Bayrunner]

very good points. I was wondering if there was a difference between the 6 and 8 logic.

Thank you.

 

[CZLN6]

Howdy Back Bayrunner:

The factors that effect torque/HP are the same for both inline and bent engine. Issues like bore/stroke ratio, compression, cam timing, displacement, to name a few. For example a long stroke/smaller bore 300 six will generate more torque down low then TransAm 302. But the short stroke, big valved, big cammed 302 will generate almost the same torque numbers, way up high in the rpm range, along with a ton more HP. The trade off is that the 300 will pull grain trucks through fields at lumbering speeds for thirty years or more. The TA 302 will be somewhat miserable in traffic and will be unlikely to last for three decades without major TLC. On the other hand, note that French Town Flyer (FTF) has built 300s that can fly high into the HP stratasphere.

I noticed your other post about building a 200 with a CI head for high torque. Know that the 200 had an over square bore/stroke ratio at 3.68" x 3.126". That would typically lend itself to HP over torque, but, as designed by FoMoCo that is not the case. The stock head/intake design is a low flow/high velocity type. Stock OEM compression ratio was 9:1 and cam timing screamed torque/high vacuum. It was taking a quick reving engine and turning it into a slug.

The biggest differences between the straight and bent engine designs has to do with fuel distributon and less crankshaft length. In both cases the bent engines win. Of course, multi carbs can solve the fuel distribution issues, but crank shaft length can only be controlled, not altered. A inline six engine with seven main bearings, that is well balanced and a has good harmonic balancer has a crank shaft that is fairly well controlled.

So, real world, compare a 200 to a 250 inline six. Both have a relatively small bore @ 3.68". The 200 a stroke of 3.126, the 250 has a stroke of 3.91". From the factory, both used the same head/intake (different CFM carbs) and exhaust. The 1966 200 was rated gross (Pre '72 standard) @ 120 HP @ 4,400 rpms, 190 @ 2,400 torque. The 250 was gross rated @ 155 HP @ 4,400 rpms, 240 torque @ 1,600 rpms. Take note that these numbers are very raw and somewhat suspious, but notice the torque rating rpm between the two.

So, again, real world, if you want to build a HP or Torque engine, using standard Hot Rodding practices, you will get the other- the only question will likely be at what rpm range.

Of course this is a very brief glimpse at a very complex comparison. I hope this was useful.

Adios, David