Using 400 SBC cylinder heads on a 305 engine
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==Steam holes== | ==Steam holes== | ||
[[File:Steamholes400.jpg|thumb|400px|Correct angle of intake side steam holes. These holes are larger than those found on factory heads]] | [[File:Steamholes400.jpg|thumb|400px|Correct angle of intake side steam holes. These holes are larger than those found on factory heads]] | ||
| − | The | + | [[File:400steam holes deck.jpg|thumb|left|300px]] |
| + | The one difference between a 400 cid small block head and any other small block head is the "steam holes" between the combustion chambers. 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 they 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 engine). | ||
| − | + | 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 [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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| − | 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 [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." | + | SBC heads with steam holes can be used on other blocks without problem by using a 350 head gasket. Heads without steam holes can be drilled for them by using the correct 400 head gasket with steam holes as a template. This can be done by hand if attention is paid to angling the drill bit on the three holes on the intake side towards the exhaust side of the head. Drill the three remaining holes straight down, 90 degrees to the deck. It helps 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. Steam holes can also be made using a drill press equipped with an adjustable table. |
==Bottom line== | ==Bottom line== | ||
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