# blocking exhaust crossover?



## bigcode99 (Jan 17, 2007)

What are the benifits or loss of blocking the exhaust crossover in the cylinder heads or intake manifold?


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## speedwrenchx10 (May 6, 2006)

exhaust crossovers for EGR or to heat bottom or carb so no EGR vavle or cold climate bock it I guess


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## bigcode99 (Jan 17, 2007)

its for warming the carb and intake. some heads advertize that they block the exhaust crossover. i was wondering why they do that. what would it gain?


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## lars (Sep 28, 2004)

Blocking the crossover allows the intake manifold to run about 50 degrees cooler than it does with the crossover open. The cooler manifold allows a slightly denser air inlet charge into the cylinders, and this has the potential to make a little more power. However, with the crossover blocked, you cannot run a divorced choke or a hot air choke - you have to either lock your choke in the wide open position, or run an electric choke.

For street driven applications, I have not noticed any difference in power with or without the crossover. For drag applications, you may see a tenth or two on the quarter. The Royal Bobcat setup used a crossover blockoff gasket as part of the Bobcat Kit.


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