OK, gotta a question. I see the stroker kits for the 302 from Summit which will stroke a 302 to a 347 and I'm aware that stroker kits add cubes via a larger diameter crank. But, I fail to actually grasp the concept. If you had a larger crank, don't you have to shorten the rods? How do you gain the 45 cubes without boring? Can someone give me some technical info; this one has been bothering me conceptually for a while now and I'm having trouble identifying how this is mathematically derived.

Thanks,

'82 F150 2WD w/351W (orig 300 I6)
Slik

 

Couple of ways they get around this, with the stoker crank they will sometimes use a different rod length, but usually it is done with pistons(or combo of both) that have the pin much higher up on the piston. This allows the rod to move much closer to the top of the bore and also the bottom of the bore(without the piston falling out). Some "notching" is required on the block to keep the rod/crank from hitting when the piston is at the bottom of the stroke, but this depends on how much you stroke it. Hope this is what you're lookin' for! Chuck P.

 

>OK, gotta a question. I see
>the stroker kits for the 302
>from Summit which will stroke a
>302 to a 347 and I'm
>aware that stroker kits add cubes
>via a larger diameter crank.
>But, I fail to actually grasp
>the concept. If you had
>a larger crank, don't you have
>to shorten the rods? How
>do you gain the 45 cubes
>without boring? Can someone give
>me some technical info; this one
>has been bothering me conceptually for
>a while now and I'm having
>trouble identifying how this is mathematically
>derived.
>Thanks,
>'82 F150 2WD w/351W (orig 300 I6)
>Slik
Let's see if I can explain this...On the less expensive kits the cranks are usually off-set ground. This means the rod journal diameters are usually smaller and you usually have to use a C*** rod of longer length to keep the piston near the top of the block. For example on a 460 you can off-set grind the rod journal throws from the normal 2.5" down to a 2.3" use a big block C*** rod and come up with close to 500 cu. in. Another way to look at it is when you increase the stroke on a crank, you increase the diameter of swing the crank goes thru as it rotates...the piston goes down further in the block one direction and it also pushes the piston further up 180 degrees of swing in the other direction (if you didn't shorten the rod the top of the piston would come out of the block at TDC). Does this make sence?

 

Yeah, I just saw a stroker kit at one of the performance sites and they used a 3.4" stroked crank and 5.315 rods and called it a 347 (however, I calculate that to a 342). The rod is nearly a little over .2" longer than stock, so they must have to shorten the piston by around .4 to get adequate clearance.

'82 F150 2WD w/351W (orig 300 I6)
Slik

 

What you missed in the ad is that you also have to bore the block .030 over. The crank is new cast construction in the kit and you get new longer connecting rods and custom pistons with the rod/pin location higher. I believe the pistons are designed for world products heads.