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02-04-2002, 06:35 PM
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CC Member
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Join Date: Nov 2001
Location: Sugar Land,
TX
Cobra Make, Engine: I had lots of little Cobras until Oscar the house thief stole all of them
Posts: 231
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Not Ranked
Header & Sidepipe
What is the primary size of the headers ( on average ) for small block and big block Ford ? Do the 4 pipes on the sidepipes match the primary pipe diameter ? I'm asking because most small block headers I've seen are 1 5/8 diameter and I really need 1 3/4.
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02-09-2002, 07:33 AM
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Senior Club Cobra Member
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Join Date: Feb 1999
Location: New Britain, CT,
Posts: 1,416
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Not Ranked
We've used the 1 5/8" pipes with good results even with 550 bhp small-block Windsor engines. Our FE headers use 2" primary pipes.
__________________
Bob Putnam
- E.R.A.-
Please address parts inquiries to eraparts@sbcglobal.net
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02-12-2002, 09:55 AM
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CC Member
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Join Date: Nov 2001
Location: WPB,
FL
Cobra Make, Engine: CMC, Supercharged Ford 5.0 & all the toys.
Posts: 511
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Not Ranked
One of the biggest mistakes I see people make on their small block is to bolt on a set of headers and sidepipes made for a big-block. 2" primaries, 3" collector. I did too, then hade my sidepipes re-made to my specs -- 1-3/4" pri, 2.5" collector. Didn't feel any high-end power loss with the blown 5.0, and picked up a lot of low-end torque.
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www.VEIsystems.com
CMC Cobra, Ford 5.0, EFI, Vortech supercharged, T5Z, 8.8 rear, MII front, 4-wheel discs, A/C, stereo.
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03-06-2002, 05:13 PM
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CC Member
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Join Date: Mar 2001
Location: Loxahatchee, Florida, USA,
Posts: 52
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Not Ranked
fordracer I put 2in headers on my 351C 4 barrel heads but I have 2 in ports on my heads seems to run fine !!!! guys say that I dont have the back presure for torck but I like what I have ??????? side pipes match the headers there you go heads have to breath right ???????? chuck
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03-07-2002, 07:23 AM
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CC Member
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Join Date: Feb 2002
Location: Waverly, Ne,
Posts: 9
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Not Ranked
If you are talking 289-351w idealy you would have a 1 5/8 header going into a 1 3/4 sidepipe collector. What you are doing is creating a set of step headers that are properly matched to your displacement. By using a larger header on this engine you will need to move the powerband up in RPM. This requires alot of camshaft, single plane race heads ect. The larger tube can be run but you will sacrifice power and torque below 3500-4000 rpm. Some af the headers I have seen come through the shop have been 1 5/8 primaries with a short 2" long section of 1 3/4 pipe to make it a slip fit on the 1 7/8 collector tubes. Unless you want to scrub off low end torque, use the 1 5/8 headers on a small block, i.e. 289-351W. moorepower
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Pat Moore
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05-05-2002, 10:51 PM
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CC Member
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Join Date: May 2001
Location: California,
Ca
Cobra Make, Engine: NAF 289 Slabside Early Comp Car with 289 Webers and all the goodies. Cancelling the efforts of several Priuses
Posts: 6,592
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Not Ranked
Primary Pipe Sizing
In ths 60's when the 289 Cobra and Daytona Coupes were running, header and camshaft science was in its infancy. Dual pattern cams were not being readily used on the small block even though the exaust port flow is pretty poor comparativly speaking and the headers used were 1 1/2" diameter at the time. An example of very poor exaust design was the short header (no primary tube length) dumping into 3" tubes used on the FIA 289 cars. The reason they didn't change was two fold. The homologation design that had been submitted by Belanger (designer) had to be retained once accepted for homologation.
Secondly there actually isn't alot of room for anything different, until the redesign prompted by the 427 SC with the collector outside the body. Thankfully the aftermarket for the smallblock was stimulated by the modern day hot rod, the 5.0 Mustang. Now we have an enormous selection of headers, cams and cylinder heads in iron and aluminum. The only really different heads available in the 60's were the Iron GT40 (not to be confused with the current production item) head that became available during development of the Ford GT40. It had a significantly oversized exaust port and flowed very well by todays standards, and the other was the Gurney/Westlake head both being rare as hens teeth!
Rick...........
Last edited by Rick Parker; 05-05-2002 at 10:57 PM..
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05-06-2002, 09:52 PM
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CC Member
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Join Date: Mar 2002
Location: so cal,
Cal
Cobra Make, Engine: I used to fix them for a living
Posts: 2,563
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Not Ranked
What manufacturer cobra do you have? You can probubly send your header out to a good custom header manufacturer as samples and have new ones made in whatever size you need. I strongly recommend Doug's Headers in anaheim ca. Your engine builder should recommend the header diameter.(350 cid, 6000 rpm 1 5/8 : 400 cid, 7500 rpm 1 3/4)The sidepipe primaries should be larger, as they are asthetic as well and what's another 10 hp?
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In a fit of 16 year old genius, I looked down through the carb while cranking it to see if fuel was flowing, and it was. Flowing straight up in a vapor cloud, around my head, on fire.
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