Drilling steam holes in smallblock Chevy heads
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The SBC 400 block was designed with steam holes in the deck and heads. The steam holes were designed to rid the cooling system of steam caused by localized heating under some conditions due to the 400 block having siamesed cylinders (meaning the cylinder's OD's are physically connected to each other due to the large bore size combined with the block having the same bore spacing as the 1955 SBC 265 cid engine). | The SBC 400 block was designed with steam holes in the deck and heads. The steam holes were designed to rid the cooling system of steam caused by localized heating under some conditions due to the 400 block having siamesed cylinders (meaning the cylinder's OD's are physically connected to each other due to the large bore size combined with the block having the same bore spacing as the 1955 SBC 265 cid engine). | ||
| − | + | SBC heads with steam holes can be used on other blocks without problem by using a 350 head gasket. | |
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| − | + | ==How to drill a head for steam holes== | |
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Heads without steam holes can be drilled for them by using the correct 400 head gasket with steam holes as a template. | Heads without steam holes can be drilled for them by using the correct 400 head gasket with steam holes as a template. | ||
*Start by marking the approximate steam hole locations with a marker or die. | *Start by marking the approximate steam hole locations with a marker or die. | ||
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The steam holes can be done by hand if attention is paid to angling the drill bit on the three angled holes on the intake side, and a starter bit is used to to start the hole straight down to make a small indentation to use to keep the bit from sliding as you lay the drill over to the correct angle, as mentioned above. The three holes that are drilled straight down are not a problem. Steam holes can also be made using a drill press equipped with an adjustable table. | The steam holes can be done by hand if attention is paid to angling the drill bit on the three angled holes on the intake side, and a starter bit is used to to start the hole straight down to make a small indentation to use to keep the bit from sliding as you lay the drill over to the correct angle, as mentioned above. The three holes that are drilled straight down are not a problem. Steam holes can also be made using a drill press equipped with an adjustable table. | ||
| − | + | ==Cooling system mod== | |
| + | If the steam holes are drilled or not, a modification to the cooling system that can help the efficiency overall is to connect the port at the top of the water pump to a '''rear''' water port on the intake manifold. Not all intakes have a water port in that location. But on many intake manifolds a pipe threaded port can be added. | ||
| + | ==Are steam holes needed?== | ||
| + | [[File:Steamholes400.jpg|thumb|200px|Showing approximate angle of intake side steam holes]] | ||
| + | [[File:400steam holes deck.jpg|thumb|left|400px|Click on image for enlarged view]] | ||
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| + | There are quite a few builders who claim the holes are not needed on an engine that will see "normal" duty, i.e. not idled for extended periods like a delivery truck, for example. Among them is noted engine builder [http://www.speedtalk.com/forum/viewtopic.php?f=1&t=30647&p=363026&hilit=steam+holes Joe Sherman] (of Joe Sherman Racing) who says, "I have built hundreds of 400 engines, WITHOUT the steam holes, and never had a problem. Guys used to send me their heads for me to drill the holes, because I only charged 80 dollars to do the job, but I never did it for my own stuff." | ||
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| + | [[File:Steamholes400.jpg|thumb|200px|Showing approximate angle of intake side steam holes]] | ||
| + | [[File:400steam holes deck.jpg|thumb|left|400px|Click on image for enlarged view]] | ||
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| + | ==References== | ||
| + | *[http://www.gregsengine.com/converting-350-heads-to-400.html Converting 350 SBC heads for use on the 400 SBC] | ||
[[Category:Engine]] | [[Category:Engine]] | ||
| + | [[Category:Cylinder head]] | ||
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