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Discussion Starter · #1 ·
Does anyone run their crossover blocked off? I have found varying opinions on this. I am debating on doing it with my 440. I'm using an aluminium (sp) intake. I live in the south sooo.....
 

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The head to head crossover through the intake ?

YES lots of people, especially those who do not really need carb heat for cold weather driveability, block those passages.
 

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Mine are non existent, either the heads i use on some motors don't have them or intakes i use don't have them
 

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Time for me to learn here, what is the advantage to blocking the intake cross over?

Mac

Smokey said:
The head to head crossover through the intake ?

YES lots of people, especially those who do not really need carb heat for cold weather driveability, block those passages.
 

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I have run vehicles both ways, and I wouldn't do it (block the exhaust heat crossover) on a daily driver unless I was highly concerned about getting every last bit of horsepower out of it. They run better when cold with the crossover un-blocked. You may lose a few horsepower on the top end when it is warmed up, but for a daily driver or a stock truck, I would leave it flowing.
 

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Im confused, so blocking the crossover makes the fuel cooler or allows for it to get hot, which one?

Moparman440 said:
I have run vehicles both ways, and I wouldn't do it (block the exhaust heat crossover) on a daily driver unless I was highly concerned about getting every last bit of horsepower out of it. They run better when cold with the crossover un-blocked. You may lose a few horsepower on the top end when it is warmed up, but for a daily driver or a stock truck, I would leave it flowing.
 

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The intake doesn't get the heat from the exhaust, and moparman they block themselves in a few years anyway so might as well do it so it doesn't hurt at all, however the intake is still sitting over the cam and the cam is spitting hot oil around in the cam and lifter valley, for it to truely be beneficial the intake runners need to be off the valley cover.
Also once you shut it off and the intake becomes heat soaked and you lose all benefit, unless you ice it
 

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Discussion Starter · #11 ·
I'm running a performer intake and doesn't the cross over heat the choke stove (if that's the right part)
 
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Yes, cooler intakes mean more power as the intake charge remains cooler. Along with what Evil was saying, it's no big deal blocking the passages. Besides, especially when aluminum intakes are used, they're gonna transfer heat much faster than cast iron, so with the oil splash and engine coolant, they're gonna warm up quickly. Regarding the choke on the Edelbrock, yes the exhaust passage heats it, but again, factor in the heat transfer rate of aluminum and it's no big deal.
 

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What the passage actually does, assuming you have a functional heat riser valve installed in the manifold to exhaust pipe connection,... (a heat riser valve that closes a butterfly in the exhaust stream, due to the action of a thermostatic spring or vacuum actuator, and creates backpressure that forces exhaust up through the passage), is allow the hot exhaust gasses to pass up through the intake manifold, and heat the base of the plenum chamber immediately underneath the carburetor, to give better vaporization of the fuel mixture during early start and run conditions.

As mentioned above, the heat sink affect of a running engine catches up with this early warming system fairly quickly; except, Macario has a BB so, the manifold doesn't get the oil splash warming that a SB does. Further, because there is considerably less contact area between the BB manifold and the rest of the engine, BB manifolds do heat more slowly and run a bit cooler (one more little horsepower advantage). But then, Albuquerque hardly ever gets really cold, so I think he'd be OK blocking the passage, because initial start-up cold weather driveability is not that big a concern..

If you have headers, you do not have a heat riser valve...
 

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Well, the intake I am using has no xover passages, and I have a splash shield under my intake in the lifter valley to prevent the hot oil from warming the intake up. It sits about halfway between the lifter valley and the intake, so no hot oil gets splashed on the bottom of my intake...except when I put the truck over on it's side.......lol
 
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