Cadillac engine knowledge
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Modifications and Swapping. | Modifications and Swapping. | ||
| − | The biggest gains in power output come with cylinder head work. Pre-'72 heads are small chamber 72 cc's and are good for around 12 to 1 compression with race gas. The '73 and later heads have larger 120 cc chambers and are a better choice for a pump gas torquer with an 8.5 to 1 compression ratio. The best bet for a pump gas premium street torque monster is a set of '77-'79 425 heads. These offer an honest 10:1 compression ratio on both 472 and 500 engines. Big gains can be made by adding larger valves and induction hardened seats. The valve sizes can be boosted to 2.08"/1.70" without worry of hitting the water jackets. The usual porting, valve unshrouding and minor bowl will work, although the short-side radius should be left alone to avoid drastic differences in airflow. Roughly 20 horses can be gained by this work alone and most of that comes from the larger valves. | + | The biggest gains in power output come with cylinder head work. Pre-'72 heads are small chamber 72 cc's and are good for around 12 to 1 compression with race gas. The '73 and later heads have larger 120 cc chambers and are a better choice for a pump gas torquer with an 8.5 to 1 compression ratio. The best bet for a pump gas premium street torque monster is a set of '77-'79 425 heads. These offer an honest 10:1 compression ratio on both 472 and 500 engines. Big gains can be made by adding larger valves and induction hardened seats. The valve sizes can be boosted to 2.08"/1.70" without worry of hitting the water jackets. The usual porting, valve unshrouding and minor bowl modifications will work, although the short-side radius should be left alone to avoid drastic differences in airflow. Roughly 20 horses can be gained by this work alone and most of that comes from the larger valves. |
Blocks should get the standard deburring. A drain hole can be drilled into the rear of the lifter valley for better oil drainback and a spillway can be added to the oval hole at the front of the block to better lubricate the timing chain and the camshaft thrust face. Incidentally, a later block has 1/2 inch oil galleries for increased flow through the block, so it makes a good performance base. If the front cover has rust pitting from the water pump, it can be saved by sandblasting and filling the pits with JB Weld and then painting. One more thing about blocks, a 472 can be made into a 500 by swapping in the 500 crank and pistons, although on '68-69 engines, a slight amount of notching is necessary at the bottom of the cylinder bores. | Blocks should get the standard deburring. A drain hole can be drilled into the rear of the lifter valley for better oil drainback and a spillway can be added to the oval hole at the front of the block to better lubricate the timing chain and the camshaft thrust face. Incidentally, a later block has 1/2 inch oil galleries for increased flow through the block, so it makes a good performance base. If the front cover has rust pitting from the water pump, it can be saved by sandblasting and filling the pits with JB Weld and then painting. One more thing about blocks, a 472 can be made into a 500 by swapping in the 500 crank and pistons, although on '68-69 engines, a slight amount of notching is necessary at the bottom of the cylinder bores. | ||
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