xhaust cross over
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6,500 Posts
Mine are non existent, either the heads i use on some motors don't have them or intakes i use don't have them
G
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·Cooler fuel mixture temp = more efficient burn.
Am I right?
Am I right?
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674 Posts
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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6,500 Posts
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
Also once you shut it off and the intake becomes heat soaked and you lose all benefit, unless you ice it
G
Guest
·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.
For those who live in a cold climate the following information may be useful.
The purpose of a heated air intake(stove):
http://www.autosite.com/garage/encyclop/ency08e.asp
The purpose of heated intake manifold(crossover):
http://www.autosite.com/garage/subsys/bamanifo.asp
The purpose of a heated air intake(stove):
http://www.autosite.com/garage/encyclop/ency08e.asp
The purpose of heated intake manifold(crossover):
http://www.autosite.com/garage/subsys/bamanifo.asp
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1,497 Posts
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...
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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3,962 Posts
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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