s3079893 Posted March 10, 2007 Share Posted March 10, 2007 Hi everyone, I'm at the stage where i'm about to build the header pipes and i was just wondering what header pipe lengths i should go with. I'm running a 5.0L with flowing heads and intake etc... and i'm planing on using 1 3/4 inch primaries. i want my power in the 3000- 6000 range Cheers Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 10, 2007 Share Posted March 10, 2007 Only an opinion, but I believe you'll need a little more flow or rpm to make full use of the 1.75" tubes. I run mine occationally to 8000, and the 1.75" tubes I have are most likely too large for my 289 as it sits. I plan on the same header tubes for the 351w in the future. Quote Link to comment Share on other sites More sharing options...
s3079893 Posted March 11, 2007 Author Share Posted March 11, 2007 Hi Terry, I geuss I would like to replicate the package on this site (3rd from the top) http://www.airflowresearch.com/ford_dyno.php What do you reckon? Quote Link to comment Share on other sites More sharing options...
blueovalz Posted March 11, 2007 Share Posted March 11, 2007 Nice link. Tough to say based on what I saw. It appears this size tube was used on nearly every engine combination shown (except two). Quote Link to comment Share on other sites More sharing options...
Guest Gr8White Posted March 12, 2007 Share Posted March 12, 2007 Go with 1 5/8".... Quote Link to comment Share on other sites More sharing options...
s3079893 Posted March 12, 2007 Author Share Posted March 12, 2007 Yeah good point terry!! i didn't really pick up on that. Ok now how long should the primarys be? Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted April 4, 2007 Share Posted April 4, 2007 I cant verify the effectivenss of these equations as I do not have the resources to test them, but everytime I come across this issue in a book the same formulas are thrown out at the reader. The formulas and the approach are as follows: If your vehicle's set up neither limits the length nor diameter required then use the following formulas working length first: Length = ((850x (360 - Exh.Vlv Opening) / Peak RPM)) - 3 Diameter = (SQRT.((Block Displ. / #of cylinders x 16.387 / (Length +3) x25)) x 2.1 If your vehicle set up does restrict either the header length or tube diameter then use the forumulas below starting w/the known variable which is not the restriction: Diameter = SQRT((Displ x 1900) / (Primary Tube Length x Max RPM)) Length = ((Displacement x 1900) / (Diameter^2 x Max RPM)) *NOTE: The articles are always vague regarding the previous two formula's reference to "displacement". Play w/the formula both ways, once w/cylinder displacement and once w/block displacement to see which answer makes sense. Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
s3079893 Posted April 6, 2007 Author Share Posted April 6, 2007 Cheers, Thanks heaps, i'll give them a try. By the way are the units i should use in these formulae are American (ie, inch etc)? Quote Link to comment Share on other sites More sharing options...
Kevin Shasteen Posted April 6, 2007 Share Posted April 6, 2007 Yes, American Units Kevin, (Yea,Still an Inliner) Quote Link to comment Share on other sites More sharing options...
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