Great job building one with your son! I always cherish time with my kids and grandkids so I hope your build brings success in the performance department and that it will be good time in the garage together.

We’d be well served with a bit more information – if you ask Tech, he can point you toward what you need in the stack-o-stuff department in terms of determining what your real compression ratio needs to be. While this is not my build, I did find this to be a great article on a 600HP streetable small block. Granted, it is a 427, but worth the read at: Small-Block Build - Street Smart - Super Chevy Magazine

One quote concerning the cam selection, “Being a dedicated street motor, we chose a hydraulic roller cam from the Comp Cams catalog. The 292XFI HR13 offered 0.584/0.579 lift split, a 242/248 duration split, and a 113-degree lobe separation angle. The lift figures were generated with 1.6-ratio rockers and took full advantage of the airflow offered by the 220 Race Ready heads from Airflow Research. Comp Cams also supplied the hydraulic roller lifters, double roller timing chain, and one-piece hardened pushrods for our test motor. Combined with the flat-top pistons, we achieved a net compression ratio of 10.8:1, a little high but totally liveable for 93-octane pump gas.”

10.8:1 will definitely be an aluminum head build but I see you’re already there.

You probably already know the pros and cons about internal versus external balance – but here’s my two cents: I prefer internal balance as it makes it a whole lot easier (and less expensive) to change the flexplate or damper if the need ever arises. When GM designed the 400 small block it was necessary to add counterweight to the crankshaft to compensate for the longer stroke. The small block internal spacing (as cast) doesn’t allow moving the counterweights away from the centerline of the crank because the weights would hit the block. So GM added weight at the flexplate and harmonic balancer ends of the crankshaft, creating the only small block that is externally balanced. As such, a lot of 383 kits use an externally balanced crank that requires a 400-style harmonic balancer and flexplate. The initial cost is definitely less expensive with an externally balanced assembly as adding Mallory to the crank throws is required for internal balancing. There is reason to believe that external weights are more likely to put a twist in the crank at higher engine speeds and that internal balance does offer durability advantages. Both Eagle and Scat offer an internal balance option for 383 stroker packages as evidenced by the kits that do not include the flexplate and damper.

As another opinion only, I wouldn’t use a Performer as it will not easily see 6,000+ RPM, rather I’d go Edelbrock RPM Air gap, Edelbrock Victor Jr, or if you can find one – Holley’s version of the manifold used on the DZ 302 engine.

Let us know what you come up with and again – good on ya for hot rodding with your son!

Regards,
Glenn