Exaust Dumps

[ZZZZZZ]

I have heard that the sidepipes on a Cobra can robb as much as a hundred horse power. Does any one know if this is true? Also, saw a add for the new electric exaust dumps, flip a switch and you are running open exaust. What your opionin on the horse power gains if you installed these on the exaust. Figure you could put them after the headers and before the sidepipes.

[ZZZZZZ]

Any one got any ideaas!

[a427sc]

Do yourself a favor. Do a search on sidepipes and mufflers. There's at least 3 hours of reading on this, especially in the Classic Roadsters.

Electric dumps?, Kind of hard to hide isn't it? If you're on the street, a good muffler set is plenty. On the track, switch to open pipes with a quick disconnect flange such as Burns Stainless etc.

Don

[Ron61]

In California any kind of exhaust bypass or dump that isn't covered by a bolted cover can get you a big ticket. Electric dumps can get the car impounded. I watched the cops at last year's Kool April Nights car show going around looking at cut outs on out of state cars and telling the people that owned them they could not use them here in this state. Some guy from Oregon with a 1957 Chevy had to try it and he got about a block while leaving the show and was getting a ticket as I walked by.

Ron

[speed220mph]

I don't think the power loss is due to the muffer, but the excessively long primary header pipes. They look neat, but the collector should be closer to the valve for correct scavenging, and more importantly, the original look would be compromised. This could be partially circumvented by going with the correct header arrangement, then dumping the header into the collection of original primaries inside the fender as has been done on a lot of Cobras.

[Bart Carter]

You would need to turn your engine past 7,000 RPM to see any HP gain from short primaries over long primaries.

[George Snyder]

I was wondering if the short headers we use on these Cars were hurting performance also. I wish I had a better understanding of this topic.
I have found this site which seems to address header designs in detail . http://www.headerdesign.com/extras/design.asp

If you get time to veiw this site, or have comments on this topic, I would like to hear them. Please post!

Thanks,
George

[Bart Carter]

One of the most enlightening talks I ever heard was when Smokey Yunick discussed headers. He said he had over 100 pairs hanging on his walls. He would design them then test them on different engines.

He said it all boils down to this: make the turns as soft as possible and try to flow everything smoothly. If you do that, you will get 90% of the benefits of a header.

I wouldn't worry about the headers. There have been many times an unequal length header has produced more HP than an equal length.

Some basic suggestions:
Make sure the headers are appropriate for the ports in your heads. If you have a choice between long and short tubes, long tubes will give you better performace in the RPM range you are probably looking for. Tube diameter will be more important to keep up velocity. A good ceramic coating will also maintain velocity better.

If you need that last 5 to 10 HP to be competetive in a racing class, long tubes designed for your RPM range might be appropriate.

[ZZZZZZ]

You see lots of people switching to the short sidepipes at track events. Has any one compared the horse power to the short side pipes vs the standard lengh sidepipes. Do these short sidepipes truely make a differnce.