Thread: SBC identification

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Pop a valve cover off one of the heads and read the casting number. Then scroll down on this page to "SBC Heads" and find your casting number and description. Being a low hp motor, I would expect the chambers to be 76cc's (Probably 333882 casting number).
Chevy Small Block V8 Casting Numbers - Mortec

Your motor came from the factory with steel shim head gaskets(about 0.020" thick), which work great with iron heads. Aluminum heads don't like steel shim gaskets because they move around a lot more than iron heads and could crack due to the incompatibility with the iron block. Composition gaskets (about 0.040" thick) pose a problem though, with the squish/quench clearance on a stock block.
Here's the problem: When your motor was produced at the factory, the piston deck height (distance from the block deck to the crown of the piston, with the piston at top dead center) was about 0.025". In other words, the block deck height (distance from the centerline of the main bearing bore to the flat surface of the block where the heads bolt on) was blueprint dimension 9.025" The stack of parts used in the motor (crank radius of 1.740", rod length of 5.700" and piston compression height of 1.560" added up to 9.000", so that the piston was down in the bore 0.025. Using a steel shim gasket of 0.020" thickness, added to the piston compression height of 0.025", meant that the piston missed hitting the bottom of the head during operation by 0.045". That dimension is called squish/quench.

Now, you are planning to use aluminum heads, which will not tolerate a steel shim gasket (they move around a lot more than iron heads and are likely to crack if held too rigidly), so you have to use a composition gasket of 0.039" to 0.041" thickness (Airflow Research recommends a Fel-Pro 1003 at 0.041" thickness) and that puts the squish/quench at 0.066", which is too wide to generate a good squish, making the motor more detonation-prone on pump gas. The tighter the squish, the less chance the motor has of detonating and the more horsepower the motor makes. Us hot rodders aim for 0.035" to 0.045" squish.

The whole reason I'm telling you this is that you will have to take a cut on the block decks and shorten the block deck height in order to run the thicker gasket and still have a good squish figure. If you cut the block to zero deck (the piston crown is flat with the block decks with the piston at top dead center), then using a 0.041" gasket will produce a 0.041" squish and you'll be golden. Of course, cutting the decks means a complete teardown, so you may just as well plan for a 0.030" overbore and fresh pistons that will work well with your new heads.

I would shoot for an intake runner volume of 180-185cc's if purchasing heads for a 350. Smaller than that and you may as well keep the iron heads. Larger than that and the motor will be a pooch on the bottom end, where you do most of your driving.

If you want to learn how to do this swap properly, get back to me when you have a head off and I'll explain how to determine the volume in the piston crown so that you can purchase heads with the proper combustion chamber volume to make the proper static compression ratio for the fuel and cam you plan to use.

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