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Eric, I was bench racing with a buddy about cylinder heads for a turbocharged engine build. He was looking to buy some inexpensive aluminum heads, and he wanted to know which flowed the best. I tried to explain that the best “flowing” (and cheapest) head may not be the correct choice for a turbocharged engine because it most likely has narrow valve seat margins to increase airflow, and being a cheap head, likely has iron valve seats. I argued that both the valve job and valve seats (and maybe even the valves too) might be fine for a normally aspirated engine, but will not transfer heat away from the valves very well, and that it will likely limit boost pressure due to detonation from the hot cylinder chamber/exhaust valves. I recommended he get the heads bare and have better valve seats installed with a good seat margin to transfer heat from the valves better, and that any small loss in cylinder head flow could be overcome by allowing for higher boost pressure because of the better thermal control. I’m not saying he needs Copper-Beryllium seats, but at least some powered metal seats or Dura-Bond “Killer Bee” PM seats?
Also, with the new valve seats, he can have the machinist make sure the press-fit is correct. Who knows how tight the press fit is (valve seats) on the cheap off-brand heads?Now that you have a turbo car, what are your thoughts?
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