Thread: SBC identification

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Any aftermarket aluminum head will flow circles around those 305 heads and make more hp, regardless of static compression ratio. It's all about filling the cylinder to make a bigger bang.

If this is a budget deal, then I would opt for some L31 heads, small flat tappet hydraulic cam, using ZDDP in the oil and a good set of 1 5/8" headers. Then, as budget permits, a high-rise, dual-plane intake such as the Edelbrock 7101 or Weiand 8150 and a 750 vacuum secondaries carb.
Here's the scoop on the Vortec heads. They are thin wall castings and tend to crack when coolant temps get too high, so if you go shopping for them, make sure you include magnafluxing in the deal with the seller before you take ownership of them. Then use a cam like the circle track guys use, Isky makes a ton of the 0.420" lift rule cams. Retainer to guide clearance limits lift with the stock arrangement, unless you want to spend the dough to completely re-engineer them and if you're going to spend that much money, you might just as well buy aluminum to begin with, so stay at 0.420"-0.430", use the stock guided rocker arms and stock springs, bolt 'em on with steel shim gaskets and you'll be fine.
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Depending on the piston crown configuration, you should be somewhere around 8.5:1 to 9.0:1, so a cam something like the Crane 10003 or Isky equivalent should do the trick.
The stock L31 350 had, I believe, 9.4:1 SCR with flat-top pistons. If your pistons are flat-tops, then use a little more cam, like a Crane 10004 or equivalent. The retainers should clear the guides with a 0.440" valve lift cam, but you will want to check clearance to make sure. If there is less than 0.050" clearance at full lift, take the retainers to a machine shop and have 0.050" "surface ground" off the bottoms of them.
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