Originally Posted by deiselpower
Hello, I was looking to upgrade my 355 with the 60103 lunati cam Brodix Ik
200's, I was looking around for a new 3.75 stroke crank to use with 5.7'' rods
and internal balance.I was looking at scat website but they don't have any
unless I go to the 6.0'' rods, after I looked on summit and the only crankshaft I
could find for my application was Eagle and I heard (also read on here) that
they are made very poorly. I have a budget of $400 without machine work so
forged isn't necessary. Should I go with the Eagle or some other company. T
Your budget will drive you to a cast crank, try to sping for steel rather than iron if you can as they will put up with more abuse and last longer. Problem with cast cranks as there isn't enough space to counter the moving part weight with a cast counterweight unless Mallory metal is put in it, this gets really expensive really fast, so if you just have to have internal balance you're dollars and reliabilty ahead to spring for a forging which due to the denser materail will usually balance interanally. Keep in mind that the need for internal balance is really only in high RPM, high output engines. For lesser engines, external balance is fine, especially when you consider that even internally balanced engines are balanced bearing bay by bearing bay, all production style cranks under balance the inner throws and make it up on the end throws, hence the big counterweights at either end where the center throw counterweight deficienies are made up.
SCAT makes a nice shaft, Eagle had some problems with thrust journal surface quality and rod journal widths a few years ago, current production appears to have corrected these issues.
Rod length will dictate the piston you use, a 6 inch rod on a 383 stroker drives the pin into the oil ring pack which requires a steel support ring to position the oil ring over the pin hole. While these seem to work well, it is a potential failure point that isn't present with a 5.7 inch rod and piston combo.
Getting the rod past the cam is a problem with either rod, best solution is a cap screw rod as you will probably have to grind for some clearance and from my perspective I rather shave a little off just the rod rather than both rod and bolt head where a conventional nut and bolt systems is used.