BORE and STROKE issues and questions

[1stgensleeper]

alright im kinda new to DSM's, but i know a fairly large amount about engines and geometry and i searched and searched and couldnt find a straight answer to this exact question.

i read that a safe bore to go to is 65mm which will allow you another bore god forbid something happen. from my understanding the 4g gets most of its power through torque due to long stroke, the only thing is, long stroke makes rod angles severe when the crank rotates the piston back up into the cyllinder creating ovaling and blowby. I also believe its responsible for the dreaded crank walk because of the sideways force on the crank journels on the pistons downward stroke. and here is my question:

Why would you take a long stroke engine and stroke it, wouldnt you want to bore it out a little bit and then decrease the stroke? My personal opinion would be to Bore it to 65mm then find a different Mitsu crank that bolts in and has a little less stroke to increase reliability and decrease problems coming from long stroke engines.

Question #2: does such a crank exist?

Question #3: if such a crank doesnt exist would boring and boring alone be a MUCH more profitable and reliable thing to do to you engine

sorry for all my little stupid question, im just all about reliability and daily drivers and longevity i want horsepower but not at the cost of 50,000 miles shortened life of my engine, i love my lil 4g i want him to live a long horsepower rich life

 

[scottsee]

on a dsm the 7 & 6 bolt 2.0 crank is 88mm. on the 2.4 its stroke increased 12mm to 100mm. the furthest you can bore is .08 over. weisco is the only company i know of that ever provides pistons for that application though im sure somone will point out otherwise. the rule of thumb is aything over .06 and you pushing the envelope on reliability! its been long known that pistion slap and cylinder wall pressure is an issue with a 100mm stroked 6 or 7 bolt 4g63. any long stroke will provide great toqure. a 4g is no exception. but when it comes to reliable HP and Failer why risk the block for minumal displacment issues by going from .04 to .06 or even .08?? just stroke it. And yes there are longer stoked aftermarket crankshafts are available. some i think are 114mm. somone correct me if thats not it.

 

[1stgensleeper]

i know a couple of my basics but im not that great with Math. What would the overall displacement then be if you were to bore it out to say .08 then reduce the stroke to 80mmm, not only in my mind would it be extremely reliable, it would rev higher and faster because of slower piston speeds due to the shorter stroke. and i realize that youd lose a little torque and be a slight bit more "Honda-ish"-high revving and low torque but youd think the reliability would increase twofold. I mean do the math: Slower piston speeds, less severe rod angle, larger bore with a nice comp ratio makes for a better more economical fuel burn, if you would oversize your valves i bet you could get alot more reliable power out of the engine instead of resorting to stroking (and increasing all those wear and unreliability factors), in my mind its just not worth it. and by all means correct me if im wrong, but please back it up with hard mathmatical or personal expirience facts NO FLAMING

oh and heres another question on top of all these, how far can you safely bore on sleeves. if id put in some ductile iron sleeves and bore them out what then could i safely go to?