That adds 6 ccs, which doesn’t sound like much, but it has a big effect. Now let’s take that 9.6:1 combination and add bigger 461 heads with a 64cc chamber.
So you can see that even slight changes make a big difference. Most production based small-blocks back in the day were closer to 0.020-inch down in the hole, dropping the compression to 9.3:1. That’s a great pump gas compression ratio-likely your specs will be slightly different. For example, a 0.060-over 283 with a 58cc chamber, flat top pistons with four valve reliefs (we’ll call that 6 cc or 1.5cc per relief), a shim steel gasket that’s only 0.018-inch thick, and a deck height with the pistons 0.010-inch below the deck produces 9.6:1 compression. Since the 283 uses a short 3.00-inch stroke, combustion chamber volume with a flat-top style piston means you really need to make the chamber size very small. The reason this is important is when we start plugging numbers into a compression ratio program-the short stroke makes adding compression difficult without going to domed pistons. Those double-hump heads generally have 64cc chambers. The problem with adding bigger fuelie style cylinder heads like the 461 or 462 is that, while these heads increase airflow over a stock 283 head, this also increases the combustion chamber volume. When Chevrolet needed to come up with a 5.0 liter engine for their jump into Trans Am racing with the Z/28 in 1967, they merely slipped a 283 3.00-inch steel crank in a small-journal 327 4.00-inch bore block and instantly had a 302ci engine.īy increasing the bore 0.060-inch on your 283, you end up with 3.935 inch bore that bumps the displacement to 292ci. The standard dimensions were 3.875 inch bore with a 3.00-inch stroke. These are great little small blocks that were small-bore, short-stroke little blocks that seemed like they would run forever. I have actually played quite a bit with 283 Chevy engines. This is going to be a very mild 292 in my street rod and I might even add a 2×3 Rochester tri-power setup on it to give it an old time hot rod look. I can get a set of those “camel back” or “double-hump” heads-I think the cast number is 462. I just finished the short block and all my friends are telling me to put a big set of heads on this to help it make power. I have a 0.060-over 283 that is now at 292 cubic inches. Here’s a question you probably haven’t got before in your Ask Away! segments.