Originally Posted by customcherry
is threr a quick way to mesure a crank to make sure u are gitting what the seller is advertising
The measure is from the main journal to the rod journal, this distance will be 1/2 the stroke.
Unless you can set this up in some Vee Blocks, it takes a good eye, typically the measure would be the distance from the middle line of the crank running through the main journals to a middle line running through the crank pin to be measured. While a measure can be taken from the top or bottoms of each of the journals to be compared, if the crank has been reground to different sizes on either or both the mains and rods the measurement of the stroke would be slightly inaccurate.
The stroke is the full distance the rod pin travels from its top most position to its bottom most position, this is why the actual distance from main center to rod center will only be 1/2 the total stroke.
Generally the SBC has a noticeable difference in stroke the 283, 302, and 307 having a 3 inch stroke so you're looking for 1.5 inches between journal centers, the 327 having a 3.25 inch stroke which is 1.625 or 1-5/8s inch on center; the 305 and 350 share 3.48 inches half of which is 1.74 or a bit over 1-47/64ths; the 400 is 3.75 which is 1.875 on centers or 1-7/8ths, this is also the popular length for stroker SBCs like the 383. 400 cranks have larger main journals than the 350, however, there are purpose made 383 stroker cranks that come with 350 sized mains.