[71 T/A]

I've heard that filling the exhaust crossover with aluminum in a set of heads gives you about a .1 improvement in e.t. I've also heard it can hurt the driveability of a street car because it'll take a lot longer for your car's engine to warm up. What's true and what's not? Is blocking the exhaust crossover a strip only thing to do?

[71 T/A]

I've heard that filling the exhaust crossover with aluminum in a set of heads gives you about a .1 improvement in e.t. I've also heard it can hurt the driveability of a street car because it'll take a lot longer for your car's engine to warm up. What's true and what's not? Is blocking the exhaust crossover a strip only thing to do?

[larry davis]

I believe "strip only" is too vague of a description. What maybe strip to one is streetable for many.
But in the loose designation, I would say no, not "strip only".
Again it would depend on how much warming up of your "street" car w/ the x-overs blocked is excessive to you. Again way too subjective.
I believe the performance gained through flow improvements and reversion loss outwieghts the minimal detractors.
I've ran two sets of Ds w/ the same on the street for years.