What is the pipe running from head to head

[maze2525]

Im sure this has been asked many times before and sorry for repost... But what are they? does it have to go back to the tb cause im doing a swap and have no idea

[phantom405]

The coolant crossover/steam vent...it does not have to be connect to the tb...that's call the throttle body bypass mod...helps keep iat's down

it's purpose is to help prevent the tb from freezing in extremely cold climates

[oleshifty]

most of the trucks have a single crossover in the front. Some of the early ls1's had an X type crossover. (I'm hoping to find one for my swap) The heads have holes in front/back. The rears are normally plugged with a bolt in cap. Late model heads have a 'melted' in plug. (that can be knocked out with a tap if you accidentally bolt the heads on the wrong side of the engine *cough* midwestss *cough*

[jbauto]

Any pics of this x pipe ?

[maze2525]

so when do the bypass where do i need to put it at or can i just buy the block offs like that are on the back of the motor