JBrady
Active Member
- Messages
- 1,776
- Location
- Houston Texas
Short but interesting question and professional answer from a real racing header builder over on speedtalk forums:
Here is a picture of one of Calvin's headers
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how important is header selection when running full exhaust?
by bc » Sun Nov 28, 2010 7:52 pm
Does full exhaust cancel out the effects to some degree of primary sizing and length of headers? Also does collect size and length matter with full exhaust?
bc
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Re: how important is header selection when running full exhaust?
by exhausted » Tue Dec 07, 2010 10:02 pm
Probably the biggest player in regards the second question is the size of a choke in the header final collector. Most collectors are way too large and allow the "stuff" in the system to more readily effect the work of the headers before the collectors. An example is say a 350SB Gen1 Camaro at say 500hp at 7500rpm engine. With a 421 header the final choke would be around 2.25" OD, a 4into1 about 2.5", while a off the shelf header would be 3.0,maybe even larger...uugghh. Anyway, the smaller chokes act as a valve or back door if you will and helps isolate the front from the back. It makes a very big difference keeping the back door shut!
The smaller the hole the happier the engine is at lower rpms and makes much more power without losing any upstairs . Can anyone see why the 421 header can put a big grin on your face?...
Calvin Elston
Elston Exhaust Inc.
Matthews, NC 28104
704-821-4494
www.elstonheaders.com
Here is a picture of one of Calvin's headers
-------------------------------------------------------------------
how important is header selection when running full exhaust?
by bc » Sun Nov 28, 2010 7:52 pm
Does full exhaust cancel out the effects to some degree of primary sizing and length of headers? Also does collect size and length matter with full exhaust?
bc
--------------------------------------------------------------------
Re: how important is header selection when running full exhaust?
by exhausted » Tue Dec 07, 2010 10:02 pm
Probably the biggest player in regards the second question is the size of a choke in the header final collector. Most collectors are way too large and allow the "stuff" in the system to more readily effect the work of the headers before the collectors. An example is say a 350SB Gen1 Camaro at say 500hp at 7500rpm engine. With a 421 header the final choke would be around 2.25" OD, a 4into1 about 2.5", while a off the shelf header would be 3.0,maybe even larger...uugghh. Anyway, the smaller chokes act as a valve or back door if you will and helps isolate the front from the back. It makes a very big difference keeping the back door shut!
The smaller the hole the happier the engine is at lower rpms and makes much more power without losing any upstairs . Can anyone see why the 421 header can put a big grin on your face?...
Calvin Elston
Elston Exhaust Inc.
Matthews, NC 28104
704-821-4494
www.elstonheaders.com
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