Hey all-

So I don't really want to build an LS Vtec, but just to get a better understanding of how/why, and try to figure out if it's possible to build a GSR motor basically out of an LS block, and a B16 head. Please read on. I've done some research but still have questions.

OK, so I beleive what most people do with an LS Vtec is to use the entire LS bottom end, crank, rods, and pistons, and then slap the vtec head on it with the extra oil lines.

What I've also heard is that what makes the power/causes the problems is an odd rod/stroke ratio. Basically that the LS motor strokes further than the GSR or B16 motors do? and that the fix is to balance the crank and sometimes use stronger rods/rod bolts. I beleive this is because the odd length of stroke puts sideways pressure on the whole setup and at the high RPM's needed for vtec, this causes extra stress that a GSR/B16 motor are not under, and can cause the motor to come unglued unless strengthened.

So what I'm wondering, is can an LS block be combined with a B16 crank to creat a Vtec engine (as opposed to an LS-Vtec engine), to my thinking it would creat a GSR engine? Will doing this eliminate the side stress on the bottom end? if so, what would one use in the way of pistons/rods to create a workable setup?

Theory's are nice, but actual experience is priceless. Thanks, Ben Inglis

 

If you put a b16 crank (77.4mm) in an ls block you'll have a 1.6l because both blocks share the same bore. You would also have to run B16B length rods to make up for the difference in the height of the blocks.

R/S ratio's are important, but only to a point. For an engine that see's lengthy high RPM use, road racing, etc., you would want a ratio somewhere in the 1.6-1.8:1 area, and im speaking of a race engine here. to prevent the cylinders from becoming oval shaped due to excessive side load. Lower r/s ratio engines actually tend to breath a little better at low rpm's and when tuned correctly, dont really give up power up top either to their long ratio counterparts.

But putting the entire GSR reciperocating mass inside a GSR block you have a basic GSR, except for the piston squirters. But by adding a b16 head to that block you have dropped compression in comparison to a gsr block, because the gsr cylinder head has smaller combustion chambers.

For street engines, anywhere from 1.5:1 to 1.8:1 works just fine.