Editing Cadillac engine knowledge (section)
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==Modifications and swapping== [[File:Mts cad head.jpg|thumb|left|600px|Cadillac HP MTS custom aluminum 76cc "FR" head, ~$3500/pair ca. 2012]] <br style="clear:both"/> ===Heads=== The biggest gains in power output come from aftermarket cylinder heads (see photo). Stock heads can also be ported for more power. MTS/CHP and others do this type of work. Pre-1974 heads are small chamber 76cc 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 1974 and later open chamber heads have 120cc chambers giving compression ratios of 7.5-9 to 1 depending on the piston used. 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 unshrouding and minor bowl modifications will work, although the short-side radius should be left alone to avoid drastic differences in airflow. Roughly 20 hp can be gained by this work alone and most of that comes from the larger valves. The 1977-'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. ===Intake=== The stock intakes used on the 472/500/425 engines leave a lot to be desired. They are a very low rise design, some are single plane, but not in a high performance sense. Also, the stock intake is of a "negative plenum" design in which the air/fuel mixture actually flows below the intake port, then back up to the port-not good for flow. It was made this way to clear the Eldorado hood, and consequently these aftermarket intake manifolds will not clear the stock Eldorado hood. MTS/CHP, Edelbrock and others make aluminum aftermarket intakes that are better suited for high performance duty. [[File:Mts single plane intake cad.jpg|thumb||left|600px|MTS/CHP single plane aluminum intake manifold]] <br style="clear:both"/> ===Block=== Blocks should get the standard deburring. 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, later blocks have 1/2 inch oil galleries for increased flow through the block, so it makes a good performance base. A 472 can be made into a 500 by swapping in the 500 crank and pistons, although on 1968-'69 engines, a slight amount of notching is necessary at the bottom of the cylinder bores. 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. ===High performance tolerances=== *Crank end-play, minimum- 0.008" *Rod side clearance- 0.035" *Top ring gap- 0.020" *Second ring gap- 0.018" ===Cam timing/degreeing=== The stock cam can benefit from advancing the cam timing 2 degrees, as these engines had retarded cam timing in stock form for emissions. Attach the degree wheel to the crank with a 9/16-18 fine thread bolt.
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