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Originally Posted by olddog
I'm in the process of pulling apart a 95 4.6 DOHC modular. I ...I haven't got it apart enough to measure the bores, but there are no ridge lines at the top. This engine has 105K miles on it. By feel I'm guessing less than 0.010 wear as I cannot feel anything anywhere, and you can still see the hone lines. Here is where it becomes relevant. This is an aluminum block with steel sleeves. I think the steel sleeves hold up much better than cast iron. This is a plus for a modern aluminum FE block, assuming they use steel sleeves rather than cast iron..
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I think the sleeves are ductile iron. Although the cast iron of the sixties for the most part may leave alto to be desired, in addition to lighter weight, the real advantage is the ability to repair the block and easily change out a sleeve(s), although you can still sleeve an iron block.
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Originally Posted by olddog
Additionally aluminum conducts heat better than cast iron, so cooling and even temps are much improved. However with the aluminum there is much more thermal expansion (think 4 times not sure). In my mind a large aluminum block push-rod engine almost has to have hydraulic lifters. With solids the valves would be mighty loose cold..
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Just the opposite, the valve lash is very tight when the engine is cold, about 0.013" for an all aluminum FE. Solids are not a problem.
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Originally Posted by Carnut427
Substitute knowledge for technology. Ford (nor the other manufacturers) knew siamesed cylinders would work. To my knowledge, Chevy was the first to do it on the 400 smallblock. Another thought is how much metal must you have minimum around the siamesed bores for the process to work? Ford could have saved a lot of money by making the cylinder walls thicker. They scrapped a lot of 427 blocks because of core shift and the sand used for the casting was so thin between the bores it wouldn't always stay in place.
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I think the main reason why auto manufacturers didn't make siamesed cylinders is for even cooling, even expansion, maintaining a concentric cylinder bore for effective ring sealing, i.e.more HP. I would think that with any given engine displacement, it would be better to have an engine designed with cooling around the cylinders than not. As the 427 was made only for NASCAR, for 7 liter displacement limit, as was the subsequent Boss 429, 426 hemi, chevy 427, etc. they designed engines with big enough bore spacing to allow water jackets for an engine of 7 liter displacement. Obviously, with siamesed cylinders, you can take the bore out bigger, compromising cooling which may or may not be an issue.