I want to build a 350 or 383, between 375 and 400hp N/A, not weigh too much, and potentially go turbo (or twin) in the future. This will be a weekend warrior/sunny day cruiser with a few drag runs a year (nothing competitive, just for fun/tuning). I don't exactly know where to start. I want to stay pretty light, so I'm guessing I should start with an aluminum block, but are they reliably strong (and strong enough for boost)? I assume most people would say go with an iron block and aluminum heads, but I would like to know some options. Or am I starting at the wrong part of the engine? Someone help me get started with planning.

 

The first 2 things for any engine build should always be the budget and what you want to get out of the engine in terms of performance and where the power is made. Once you establish those grounds, you can start to pick parts to help you get there.

When I started to plan my engine, I started with the heads and cam. I went large, knowing I wanted a high rpm (3000-7500) powerband for road racing. I knew my budget was flexible over time. So, those being decided, I opted for an Isky solid roller (3200-7500) and AFR 220 heads.

For you, since you will boosting in the FUTURE, one of the biggest issues is part selection. Parts for n/a horsepower are usually not very cooperative with boost. Therefore, you will have to make a choice, and I would do the later of these. First, build for N/A now, then build for boost. Or, build for boost, live with what you are dealt with, then boost and be happy.

Compression is key here. Boost likes lower compression, say, low 8's:1. Now, for N/A horsepower, you need to match the cam to the compression, or at least get it in the ballpark. Cams that are larger and usually associated with 400hp NA engines (such as the Xe274 or similar) may end up being too much for a low 8's compression motor and the valve timing will end up killing low end grunt, until that is, you go boost. Now, once you boost, of course you can run a larger cam as it increases cylinder pressure. Ahh decisions decisions.

What type of power are you looking for (and where RPM-wise) with boost?

As far as blocks are concerned, both will probably hold the power you are seeking. It's just a matter of do you want to front the cost for the better machining and whatnot found in aftermarket aluminum blocks. Better machining leads to things like better oil control and less casting flash.