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07-05-2008, 06:47 PM
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CC Member
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Join Date: May 2008
Location: taihape,
nz
Cobra Make, Engine: keith craft 427, tko600, very shiney pile of parts
Posts: 45
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Not Ranked
header size matters?
Hi,
i can get 1 7/8"primarys premade or should i get specially made 2" primarys . As there's not much restriction in the rest of system will it make a difference on my kc 427 sbf as i've been told full length under body pipes make better power anyway?
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07-05-2008, 07:10 PM
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CC Member
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Join Date: May 2005
Location: Riverside,
CA
Cobra Make, Engine: Cutting Edge, Boss 429
Posts: 377
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Not Ranked
tuska,
That is a great question for your engine builder. I am sure he would have an opinion.
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07-05-2008, 07:39 PM
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CC Member
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Join Date: Jan 2002
Location: Bridgewater,
NJ
Cobra Make, Engine: B & B
Posts: 1,323
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Not Ranked
I have watched a few episodes of Horsepower TV (SPIKE) where they dyno test different products including headers. Size, length, bends and other factors do make a difference. Nothing major from what I remember but definately worth picking the right size, etc. I think you can watch (Buy) episodes from iTunes.
BossCer's comment was good. Match the headers with the engine for the best effect.
__________________
Just enough knowledge to build a cobra and be dangerous...
You can observe a lot from just watching.
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07-05-2008, 10:35 PM
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CC Member
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Join Date: May 2006
Cobra Make, Engine:
Posts: 16
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Not Ranked
1 7/8" will be fine. The air flow will be more than enough. If you are trying for a world record in some event that nobody cares about then I would suggest that you go for 2".
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07-05-2008, 11:18 PM
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CC Member
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Join Date: Mar 2003
Location: Arkadelphia, AR,
AR
Cobra Make, Engine: Kirkham 427 brushed aluminum with Keith Craft 527C.I. all aluminum FE
Posts: 992
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Not Ranked
The 1 7/8 will be fine for what you are doing. You want to make sure they are not blocking the parts at the head opening. The next restriction will be the sidepipe muffler size. I have seen some of these as small as 1 1/2 and that really restricts the Hp as well. Thanks, Keith Craft
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Keith C
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07-06-2008, 12:29 PM
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CC Member
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Join Date: Mar 2006
Location: San Marcos california,
CA
Cobra Make, Engine: 1989 KCC from South Africa Right Hand Drive
Posts: 1,601
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Not Ranked
Primary pipe diameter and length do make a difference.I suggest looking up various dyno runs on similar motors to yours.You will get an idea as to what would be best.The 17/8 sounds big enough to me (thats what I run). The same as intake runner length makes a diffs so does the exhaust dimensions. Bigger is not necessarily better,.....in this case...anyway!
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07-06-2008, 01:50 PM
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CC Member
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Join Date: Feb 2001
Location: St. Louis, Missouri,
MO
Cobra Make, Engine: SPO 2715
Posts: 1,648
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Not Ranked
Quote:
Originally Posted by Keithc8
The 1 7/8 will be fine for what you are doing. You want to make sure they are not blocking the parts at the head opening. The next restriction will be the sidepipe muffler size. I have seen some of these as small as 1 1/2 and that really restricts the Hp as well. Thanks, Keith Craft
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This is what I have found to be true.
Using the 205 AFR heads, the standard SPF headers blocked part of the exaust ports and hurt hp.
2" SS headers were opened up at the exaust ports and helped hp (45hp) Grinding the blocked part on the 1-7/8" will do the same.
Work on the mufflers.
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07-07-2008, 07:14 PM
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CC Member
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Join Date: May 2008
Location: taihape,
nz
Cobra Make, Engine: keith craft 427, tko600, very shiney pile of parts
Posts: 45
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Not Ranked
I'll look into mufflers as sugested...literally !! And port match the manifold plates to the head. cheers glen
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07-07-2008, 07:39 PM
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CC Member
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Join Date: Oct 2006
Location: Mission Viejo,
CA
Cobra Make, Engine: Hi Tech 533
Posts: 65
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Not Ranked
I used these spiral mufflers in my sidepipes and did pick up a little horsepower.
www.spiralturbobaffles.com |
07-14-2008, 01:16 AM
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CC Member
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Join Date: May 2008
Location: taihape,
nz
Cobra Make, Engine: keith craft 427, tko600, very shiney pile of parts
Posts: 45
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Not Ranked
Are your spiral baffles similar Db to glass packed side pipes or do they have a tone of their own?
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07-14-2008, 09:46 AM
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CC Member
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Join Date: Mar 2007
Cobra Make, Engine:
Posts: 102
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Not Ranked
mufflers
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07-14-2008, 10:08 AM
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CC Member
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Join Date: May 1999
Location: Tyler, TX U.S.A.,
TX
Cobra Make, Engine: ERA, Ford 428 SCJ
Posts: 332
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Not Ranked
What about no mufflers? Least restrictive. The downsides are your neighbors hate you and your neighbors 3 blocks over hate you.
I took mine out for a test drive before tearing i all down and I'm still grining.  |
07-30-2008, 09:51 AM
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CC Member
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Join Date: Jan 2004
Location: Wayne,
NJ
Cobra Make, Engine: Contemporary 482 all aluminum Tunnelport Self built and owned since 1980 frame#0000017 and owner of frame CCX 33961 looking for an FIA body to go with it
Posts: 428
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Not Ranked
Quote:
Originally Posted by Red S/C
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I used this from speedway looks the same but much cheaper
http://www.speedwaymotors.com/p/1736...xhaust%20auger
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Cobrarich
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07-30-2008, 01:14 PM
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CC Member
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Join Date: Jul 2001
Location: Senoia,
Ga.
Cobra Make, Engine: 427SO with big twin autolite inlines on custom intake, jag rear, top loader, wembeldon white, guardsmen blue stripes
Posts: 3,155
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Not Ranked
Someone told me to come off the block at least three inches before making the first bend, not sure it matters but I did it when I made mine?.
__________________
Perry
Remember!, there's a huge difference between a 'parts' changer, and a mechanic.
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