Cadillac engine knowledge
(→Modifications and swapping) |
(→Modifications and swapping) |
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The biggest gains in power output come with cylinder head work. Pre-'74 heads are small chamber 76 cc's and are good for around 12-13 to 1 compression when a flat top piston is fitted. Race gas, alcohol or propane fuel must be used. The '74 and later open chamber heads have 120 cc chambers giving compression ratios of 7.5-9 to 1 depending on the piston used. The '77-'79 425 heads have 108cc chambers giving about 10:1 compression ratio depending on the piston used. The 425 heads have restricted air flow due to their port design making them the least desirable for modification. The head gasket is different as well. Big gains can be made by adding larger valves. The valve sizes can be boosted to 2.19"/1.84" without worry of hitting the water jackets. The usual porting, valve un-shrouding 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. | The biggest gains in power output come with cylinder head work. Pre-'74 heads are small chamber 76 cc's and are good for around 12-13 to 1 compression when a flat top piston is fitted. Race gas, alcohol or propane fuel must be used. The '74 and later open chamber heads have 120 cc chambers giving compression ratios of 7.5-9 to 1 depending on the piston used. The '77-'79 425 heads have 108cc chambers giving about 10:1 compression ratio depending on the piston used. The 425 heads have restricted air flow due to their port design making them the least desirable for modification. The head gasket is different as well. Big gains can be made by adding larger valves. The valve sizes can be boosted to 2.19"/1.84" without worry of hitting the water jackets. The usual porting, valve un-shrouding 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 | + | Blocks should get the standard de-burring. A drain hole can be drilled into the rear of the lifter valley for better oil drain back 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 [[Pitted rust|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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