Building a GMC 702 V-12
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| + | Note the difference in design of the lifter galley over a GM V-8. More to come..... heads next and that is just as interesting, right down to the sodium filled valves. | ||
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| + | == Heads or rather Head Ache == | ||
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| + | It is said that all the power id developed in the heads and the heads GM put on this engine just do not equate to any performance rule. Small valves, flat runners large stems poor angles and the list goes on. They do have machined combustion chambers so that makes for some consistency vs standard as cast surfaces. Of the heads available, I believe that anything from the 305, 351, 401, 478 V-6 aside from the ones that are V-12, will bolt up BUT there is significant variation in valves and in what was called the magnum heads. Right off the bat, the magnum heads require magnum exhaust and intake manifolds (hence I am now building custom stainless steel headers from custom plasma cut flanges). I will get into that in a bit but my advice for cost and simplicity is to stay with the stock stuff unless you are addicted to HP like me. The basic V12 heads have large stem diameter valves which are sodium filled. the associated intakes have all the right cylinder numbers on them so you get the cool 1-12 numbering on the rear manifold. I went to magnum because the port sizes are significantly larger and to me that means better flow. According to those in the know, a good ported standard head will flow as well as a ported magnum. I believe the has a lot to do with the magnum exhaust port design (I have a neighbor who has been porting heads since Harvey Crane opened shop in Orlando and Daytona was still run on sand) and the fact that the runner is flat and almost in the same plane as the exhaust valve. I will take some time here to document what I have collected as I am by no means in a position to recommend what will be best for you other than how to be cheap. | ||
[[Category:Engine]] | [[Category:Engine]] | ||
[[Category:Good articles]] | [[Category:Good articles]] | ||
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