I am in the process of tearing down a lq9 to build a stroker motor with. I will be going with a 4.030 bore, and I am trying to decide on which crank to go with. What are the benefits/drawbacks to different stroke cranks. I am looking at 4.000, 4.100, and 4.125. This engine will be a street car that sees some track time, and will see nitrous in the 150-250 hp range.

Thanks for any input you guys might have.

 

The draw backs are the ring stacks on the longer strokes. Your cylinder never changes legnth, but you increase stroke. That in turns makes you stack the rings tighter in order to get it to work. Your piston also comes farther out of the bore at BDC causing some rocking, which can add to wear. When you shorten the stack, you decrease the integrity of rings and the areas in between. It's deffinatlly not optimal for power adders, but would work all day in a N/A application. Your best bet, should you decide to go with the longer stroke, would be to talk with Erik (racer7008) of HKE. He has dealt with alot of long stroke cranks and is very good at wroking with Wiesco on developing pistons for there intended use. I would imagine he could get you something to work in the 4.100" range w/ a 150 shot. Anymore is pushing it, nitrous wise.

 

Thanks for the info. I will look into it more. I am just into the planning part right now, so I just want to get as much info as possible before I make my decision.

 

If you plan to primarily spray more than 150, it would be wise to go with the 4".

 

I am currently building a 408 stroker for my truck. I did research for a couple of years while I was saving the money. All of the folks that I talked to: sponsors on this site, piston manufacturers, engine builders . . . everyone told me not to exceed a 4 inch stroke if I wanted durability. Another thing, get your block sonic checked first. I had this done and I knew that my number 8 cylinder would be about .083" thick on the aft (non-thrust) side after boring/honing to 4.030". Everything else is good with about .100" on the non-thrust sides and close to .250" on the major and minor thrust sides. I'll be running normally aspirated and just about 9.5:1 Static CR. However, with higher compression, higher RPM's and a power adder, I wouldn't feel so comfortable. You need to check this out. Several reputable shops that I talked to don't like to routinely bore the 6.0 L iron block more than about .010" oversize and avoid strokes longer than 4.000" altogether. Now if you were talking about a tall deck Warhawk or LSX block, that would be a horse of a different color on max stroke and bore.

Steve

 

Is that the case with the soon to be released LSX block or the warhawk? Seems like that is the primary method of getting big cubes.