I was doing some research tonight about how to get more cubic inches and it arose a big question with me. Why has nobody took a set of stock cylinder, bored them to 3.932 like a 107 build, and use a 4 5/8 crank? If my math is correct this would give you a 112 cubic inch without having to bore the cases. Is this feasible or am I completely out of my mind here?

 

I would imagine that custom pistons could be ordered,(?) but a 107"er, set up correctly is a very formidable powerplant.
Scott

 

Main reason I am interested in a 112 is because I amgoing to do crank work anyway so figured might as well go to a 4 5/8 crank as Iam a believer that longer stroke gives you more torque which is what I amafter.

 

JMHO but I think you are going the wrong way.
How much torque an engine can make is based on its cubic inches. Torque comes from how much air the engine can ingest every intake stroke. The more the cubic inches, the more air it can take in every stroke.

How much HP an engine can make is based on the total valve area. HP comes from the total air the engine can ingest per unit time, like every second. The intake valve is typically the largest restriction for air flow in an engine. Therefore, an engine with more intake valve area (total valves in the engine x valve area) can ingest more air than one with less valve area. Or, it can rev higher before it runs out of breath. Higher revs mean more HP.

If we look at an oversquare engine, its larger bore allows for larger valves to be used. Therefore it can make more HP than the same cubic inch engine with a smaller bore. That’s it; it’s just that simple. The old axiom that long stroke engines make more torque is related to this. It’s not that they make more torque, its just that they can’t make HP because the valves are just that much smaller to fit inside the smaller bore.

Then you must consider the piston issue. Like Scott pointed out, there is not off the shelf piston for that configuration; you should asking yourself why?? Associated with the piston is the piston speed, sidewall loading, scuffing, heat all the other issues associated with the accelerated piston speed that configuration will generate and you are putting those loads on a cylinder spigot that some think is too thin for shorter strokes.

The lower unit has to come out to replace the crank; you have to do that anyway. Don't reinvent the wheel and **** away a bunch of money to end up with a motor that won't deliver. Stick with tried and true configurations; spend the extra $300 or whatever it costs to have the cases bored for larger cylinder and build a 117" motor; 4.125" bore x 4.375 stroke. Headwork and the right cams and it will deliver neck snapping torque without all the issues that will come with your stroker plan. JMHO.

 

g2shuck, you are going to be fun to follow! I cannot imagine a well built 107 not being enough for anybody. You already put in the 555s if I remember right, just get a nice 107 kit with headwork, tb etc - you will be smoking.

 

Alan I am obsessed with power. I have a 1000rwhp diesel drag truck in the driveway that I daily drove for almost 6 months until riding season started. After talking to a couple engine builders today I am kind of sad that I did the tw-555 cams instead of the t-man 590's

 

Those .590's are good, but there are others out there that will offer even more.
As djl has pointed out, a 117" engine can be VERY powerful, but if looking for all the gusto, then a 124".
They carry a 4 5/8" stroke, and combined with headwork, and a cam that compliments your riding wants/needs, you'll not be lacking anywhere.
Scott

 

Scott,

How much of a difference would I see between a 117 and a 113? I can get a really good deal on a set of new 4.060 cylinders and pistons to build a 113. I know the 4.060 cylinders do not come perfectly straight so I would get the 0.010 over pistons and have the cylinders honed to the pistons.

 

Can I get an "Amen"? Set up right, TMan's 590 is a runner.

 

Not trying to derail the thread but what are we talking about here!!!^^^