blocking off exhaust cross over
More Turbo
Joined: Jun 2001
Posts: 571
Likes: 1
blocking off exhaust cross over
soon I will have to remove my intake to stop a leak. I have read a few things on here about some people blocking off the exhaust cross over in the intake to obtain a cooler air charge.
what is the best way to do this. how much difference will the cooler air charge make?
what is the best way to do this. how much difference will the cooler air charge make?
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
blocking off exhaust cross over
If you have a cast iron intake, don't do it. Your drivability will suffer.
If it's alum, don't laugh but I've used a kitchen knife. It's just about the right size plus made out of stainless steel.
As far as improvment, I would guess around 2 to 5 percent. You will notice a bit more torque.
Barry
If it's alum, don't laugh but I've used a kitchen knife. It's just about the right size plus made out of stainless steel.
As far as improvment, I would guess around 2 to 5 percent. You will notice a bit more torque.
Barry
Cargo Master
Joined: Jul 2000
Posts: 2,281
Likes: 18
From: Northern California
blocking off exhaust cross over
I blocked mine off because of the CR and wanting to prevent pinging, with a colder intake charge you can run a higher CR and more advance without pinging and every little bit helps, but it really depends on the engine, for a stock setup you see little to very little change. If your in a colder area you might want to pass on this.
I used a product called quick steel, it's simular to JB Weld but holds a bit more temp. I like the idea of an old kitchen knive, cheap and effective.
If you want to make a noticeable difference, draw cold air from the side of the rad to the air cleaner (I've found several stock setups at the junk yards), then block off the crossover and adjust the timming for max adv without pinging under load.
I used a product called quick steel, it's simular to JB Weld but holds a bit more temp. I like the idea of an old kitchen knive, cheap and effective.
If you want to make a noticeable difference, draw cold air from the side of the rad to the air cleaner (I've found several stock setups at the junk yards), then block off the crossover and adjust the timming for max adv without pinging under load.
More Turbo
Joined: Jun 2001
Posts: 571
Likes: 1
blocking off exhaust cross over
>If you have a cast iron intake, don't do it. Your
>drivability will suffer.
why is this?? I do have a cast iron 4-v intake(cast # C3AE9425B). I have alwys heard that a cooler charge is better.
I know that cooler air is denser and therefor results in a better air-fuel mixture. I know a fellow who races super late models on dirt track and he puts ice in his air intake to acheive a cooler air charge.
I live in Tennessee so winters aren't to bad here and I have a manual choke carb.
just wandering why this isn't a good idea for a cast iron intake?
>drivability will suffer.
why is this?? I do have a cast iron 4-v intake(cast # C3AE9425B). I have alwys heard that a cooler charge is better.
I know that cooler air is denser and therefor results in a better air-fuel mixture. I know a fellow who races super late models on dirt track and he puts ice in his air intake to acheive a cooler air charge.
I live in Tennessee so winters aren't to bad here and I have a manual choke carb.
just wandering why this isn't a good idea for a cast iron intake?
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
blocking off exhaust cross over
Street driving and racing are two different things (at least they should be). Blocking off the crossover will make your engine cold-blooded and drivability will suffer. Iron conducts heat slower than aluminum so a cold iron manifold takes longer to warm up. When vaporized fuel hits the cold manifold it condenses and puddles out into liquid, especially on the floor. That’s why those ribs are down there, more surface area like a radiator. The unvaporized fuel just washes off what little oil there is on the cylinder walls and then goes in the crankcase. Also, factory iron manifolds usually don’t have very good fuel distribution to begin with so the heat helps here too by keeping whatever fuel you have in suspension. There are exceptions to this like the “S” manifold, it has pretty good distribution.
I'm gonna have to dig up some old hot rod books that explained this much better.
If you climate is mild you can probably get away with it but if it gets cold and damp, your carb. will ice up.
I’ve heard a good compromise is to block one side only.
Barry
I'm gonna have to dig up some old hot rod books that explained this much better.
If you climate is mild you can probably get away with it but if it gets cold and damp, your carb. will ice up.
I’ve heard a good compromise is to block one side only.
Barry
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