Thread: Stroker SBC's using 5.6 400 rods

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Originally Posted by 1gary

.030 or .040 over 350 block with using the over sized 350 piston and a 3.75 stroke and the stock 400 rods which are 5.6.Comments or input??

Yes it is kind of the old school of doing things.

Most fellows talk it down because of rod angularity which puts more force on the piston skirt against the cylinder wall and the other problem of crank counterweight to piston skirt clearance, but hey, the GM engineers designed the darned thing originally with those short rods. I wouldn't be so concerned personally about the angularity, but you have to clearance for the skirt to counterweight thing. I have carved piston skirts for clearance on my personal builds before and found that if I get the weight the same on all of the pistons, it works out fine. There may be some interference between some lobes of the cam and some of the rod bolts. Either grind on the bolts or use a reduced base circle cam for clearance. You don't need much clearance, just check it on your mock-up with the tip of a tie-wrap. Also, there may be a little interference at the pan rail with the big end of the rod, but a little grinding will take care of that. Again, use the thin tip of a tie-wrap to check clearance. A miss is as good as a mile. I'm sure you know you'll have to reduce the main bearing journal diameters on the crank also. As far as the short rod making less power than a longer rod, Iskenderian says it just ain't so. He says that because the piston parks for an instant longer at the bottom with a shorter rod, you can leave the intake valve open another 1-2 degrees and pack the cylinder a little better to make more power than you could with a longer rod. Personally, I have never measured the difference, I just lean on the experts. Longer rod, the piston parks for an additional instant at the top of the bore. Shorter rod, the piston parks for an additional instant at the bottom of the bore.