[DeTomaso] modified port plates for 180's

JDeRyke at aol.com JDeRyke at aol.com
Mon Jan 5 16:38:49 EST 2009


FWIW, most info says that the entire bottom half of a stock 4V exhaust port 
is unused; hot exhaust flow at 300 ft/sec comes straight out so the factory 
attempt to make it curve sharply only works in combination with thick-walled cast 
iron exhaust manifolds. The port plates I've seen simply lay in the port 
although one builder drills & taps screws to keep his thin plates from vibrating 
audibly like a clarinet reed. Other port-plates are cast bronze or thick 
stainless; being much thicker they don't vibrate (much).

Cutting away the stock 4V exhaust port is a NASCAR trick done back when 
351-Cs were competing for money. Since the part of the head cut away has no water 
inside, its pretty simple. Then a steel or aluminum slab is bolted on and 
exhaust ports are cut into it, in a much raised position (which is not simple- or 
cheap to hire done). FWIW, this is exactly what SVO aluminum heads have for 
exhausts but in a much stronger integral form. For drag racing and maybe on the 
street, cut iron heads worked OK but in long-distance races, mechanics found 
that the remaining section of a cut iron head (about 1" thick) cracked and that 
part of the head did have water in it.... Cheers- J Deryke


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