Hi guys... Wondering if any of yall have run exhaust stubs like the old Spitfires and P51's did. A few inches long, slash cut off... poking out the side of the hood with no muffling of any type. Always heard that running with no headers makes the exhaust valves go, but I'm thinking of a rod that could pull off the look!
I dont know if it would run all that great...I think it would look neat though. Maybe if you are running a hood you could make them longer under the hood through some bends, then only poke out a few inches on the side? Just my opinion.
i've heard the same about the valves but some bends might provide a little back pressure, would deffinately look bad *** though
When I was building my headers I ran the engine with the flanges and some curved starter tubes I had welded into them. Sounded cool and the flames were neat but being worried about the valves I didn't run it very long.
This is how the motor in the 41 looks like, I'm in the process of building a set of headers. I only run it for short bursts too.
I think those are called zoomies and even on the spitfire they were more than a couple of inches long.
Hmm... What exactly happens to exhaust valves with to short of a header? Its bad, is the depth of my understanding... Nice car, but the nose cone is a bit odd... at least without a prop behind it!
I think the rule is 18". So I'm running 18" zoomies straight off the head in my 2.3 powered roadster. Looks, *****in, but it's not on the road yet, so I can't say much about them.
losing alot of low end torque and warping the valves is what happens 18"is min as stated before.Scavenging helps build power on the low end and that is where torque loss comes in. It helped fuelers not blaze the tires so bad and make big end power in the early days when tires where used as a clutch.
the bend at the end of the pipe and also the way they pinch helps alot for the back pressure and wouldnt allow the cold air to get to the heads so fast.
As stated above...The risk to the valves is when you shut the engine down, cool air is exposed to the hot valves, possibly causing them to warp if their in the open position, or even to crack if the carbon content of the alloy is high enough. Header length directly effects torque curves. As you shorten up the header primary length, or increase the diameter of the pipe, the power band of the motor moves to the right (higher RPM range). So super short zoomies will make absolute **** for bottom end torque, and you'll have to spin the hell out of the motor to get peak horsepower out of the motor. Sure, they'd look cool, but its gonna come down to how much power you are willing to sacrafice for looks.
Well, for sure this system would have zero scavenging ability. How do the 60's rods with 8 full length pipes out the back do for power?
I personally think that individual zoomie type pipes on a street car sound like ****. Some form of collector makes a much more pleasing sound. Most straight pipe exhaust, such as the lakes headers style, sound better because of the collector. Individual pipes also lose the scavenging effect, as stated. A little back pressure helps low end as also pointed out. All this is also not stating the obvious that individuall short pipes are loud as hell and you will attract a lot of attention, and not just from fellow rodders.
The longer pipes helped the low end a bit and mellowed the sound a ton. Something that you have to remember about those Rods in the magazines is that they weren't common on the road everyday cars. especially in the '60 a lot was sacrificed for looks on a show car. that was where the "saying all show and no go" came from. Anytime you use a zoomie type of exhaust no matter how long (or short) the tube its going to be peaky, it'll make a lot of zot in a very narrow band. You drive those type cars with the gears not the gas peddle. Something I might add here, if I had a big allison to run in a rod I'd run zoomies.
So,how did the aircraft engines get away with short zoomie stacks ??? Seems like the air at al***ude would be much colder , besides engine damage on an airplane has more consequences than engine damage on a car...Just a thought....
As long as the motor is running cold air is a real factor its when you shut down. Those guys weren't like us they had a ground crew, when they landed the exhaust should have been capped. Those were also high maintenence machines not at all like our cars that get driven parked and driven again.
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