Headers/Megaphones/Cookie Cutters
12-20-2001, 07:40 PM
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Headers/Megaphones/Cookie Cutters
Ladies and Gentlemen:
This season I'm going to campaign a '71E in H-Stock. I'm thinking about using headers, does anyone have a particular type or diameter they recommend. I'm thinking that smaller diameter is better to maintain the torque of the "E." Also, I've seen the racing megaphones used, and some of them have "cookie cutter" inserts in the pipes, a number of metal vanes arranged in a star shape around a tube in the center of the pipe. What purpose do these serve?
Having said that, there's the advantage of sticking with the current SSI setup, no additional cost, and it would be legal at Lime Rock and around Manhattan (my test track). Anybody BTDT and have strong opinions about it?
Many thanks in advance for any replies.
jCf
This season I'm going to campaign a '71E in H-Stock. I'm thinking about using headers, does anyone have a particular type or diameter they recommend. I'm thinking that smaller diameter is better to maintain the torque of the "E." Also, I've seen the racing megaphones used, and some of them have "cookie cutter" inserts in the pipes, a number of metal vanes arranged in a star shape around a tube in the center of the pipe. What purpose do these serve?
Having said that, there's the advantage of sticking with the current SSI setup, no additional cost, and it would be legal at Lime Rock and around Manhattan (my test track). Anybody BTDT and have strong opinions about it?
Many thanks in advance for any replies.
jCf
12-21-2001, 10:02 AM
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Mr. Sasquatch:
I don't personally have an early 911, I have an 84. Several friends have early cars and this is what I have been told. SSIs are nearly perfect for 911 motors under 2.7 liters so headers won't give you much, if any advantage, plus bye bye heat. I slapped some SSIs (I know, the pipe diameter is 1/8" too small) with supertrapps. With the caps on, the car is quite enough on the street, except under full throttle when it gets a little on the loud side. On the track, I pull the caps off. With the caps on, I am under the noise limit at Summit Point which is 103db. Not sure what it is at Lime Rock. Megaphones will be too loud (I have a set of those in the garage). Like I said, I think SSIs and supertrapps will be a good combination for you. Just my opinion.
I don't personally have an early 911, I have an 84. Several friends have early cars and this is what I have been told. SSIs are nearly perfect for 911 motors under 2.7 liters so headers won't give you much, if any advantage, plus bye bye heat. I slapped some SSIs (I know, the pipe diameter is 1/8" too small) with supertrapps. With the caps on, the car is quite enough on the street, except under full throttle when it gets a little on the loud side. On the track, I pull the caps off. With the caps on, I am under the noise limit at Summit Point which is 103db. Not sure what it is at Lime Rock. Megaphones will be too loud (I have a set of those in the garage). Like I said, I think SSIs and supertrapps will be a good combination for you. Just my opinion.
12-21-2001, 02:21 PM
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If I'm not mistaken the vanes at the end of the megaphones were to help with the scavenge effect or minimize the turbulance of the exhaust gasses from the megaphones, helping them to breath better.
I used a pair on my 81SC and boy was it loud but, it was also nice to hear about the flames produced by them and have people behind you back off quickly when they see them.
I used a pair on my 81SC and boy was it loud but, it was also nice to hear about the flames produced by them and have people behind you back off quickly when they see them.
12-21-2001, 09:54 PM
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<STRONG>With the caps on, I am under the noise limit at Summit Point which is 103db. Not sure what it is at Lime Rock.</STRONG>
12-21-2001, 11:44 PM
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jCf:
I think Bill put the kibosh on the megaphones idea for Lime Rock, they have the most restrictive noise regs in the US, right now.
I will just tell you that megaphones will simply make the low and mid range power evaporate. Great, great sound but they only add power at the very top with cams that are lots more aggressive than the "E" cams are.
Headers in 1 5/8" will be fine for power but will not supply the heat needed for the MFI pump thermostat and the car will run far too rich. Unless the pump is modified, I would stick with SSI's and a Factory-type twin pipe sport muffler for best power and torque.
The "cookie cutter's were there to arrest the cracking that these were very prone to do,......I'm an "old guy" and I remember that stuff,.... .
I think Bill put the kibosh on the megaphones idea for Lime Rock, they have the most restrictive noise regs in the US, right now.
I will just tell you that megaphones will simply make the low and mid range power evaporate. Great, great sound but they only add power at the very top with cams that are lots more aggressive than the "E" cams are.
Headers in 1 5/8" will be fine for power but will not supply the heat needed for the MFI pump thermostat and the car will run far too rich. Unless the pump is modified, I would stick with SSI's and a Factory-type twin pipe sport muffler for best power and torque.
The "cookie cutter's were there to arrest the cracking that these were very prone to do,......I'm an "old guy" and I remember that stuff,.... .
