Quote:

Quote:

whats the benifit of running a 4.250 crank, 7.1" rod on a street engine?
thats pin must be so far up the piston I can't see it lasting 5k on a street engine.
or am I wrong?




The compression height with a 7.1 rod & a 4.25 stroke is still 1.48 Plenty of street motors are considerably shorter... Obviously the shorter piston is considerably lighter... AndyF does seem to favor the 6.8 rod combo...



I went 6.800 long rods on the motor I built for the book becuase there were a lot more choices for pistons and rods then. But since then, some more vendors have come along with both pistons and rods so if I was building a motor today I'd probably take another look at it.

SCAT has cranks now that weren't available a year ago, K1 has cranks that I didn't know about when I wrote the book. Compstar has some new rods available, etc.

Even with the 7.10 long rods and the 4.250 stroke the piston is still tall enough to be very conservative. The rod ratio is good, the rod is long enough to keep the piston skirts up off the crankshaft counterweights, etc. All around a great combo. No reason a motor like that wouldn't go 100,000 miles if you built it like an OEM engine.

The slightly shorter 6.80 rod also works just fine. There are a few oddball rods out there such as 6.850 and 6.900 but you'll probably need semi-custom pistons if you run those.