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By Litshoot - Last Month Hi,  I'm looking to build myself a set of headers. im thinking tri y might be a good option packaging trying to keep lengths close to equal. 180° is a struggle crossing over, but would 135° pairing be of any benefit? if im looking correct that would pair the outer 2 and inner 2 runners on both heads. Haven't seen a ton of information on headers and calculators seem to give me some outlying runner recommendations. 73" long 3/4 diameter primaries for peak torque at 4k. i know im not going to optimize, but id like to build as decently correct designs. for some reason im not able to get expected results for y blocks from free online calculators, although work normally when using my big block ford specs.   thanks Seth By Joe-JDC - Last Month Making the tubes exactly equal length is not critical for performance.  Routing and pairing of tubes is more important.  Firing order will also dictate which tubes are paired for Tri-Y for best performance. FPA makes an excellent header for the Thunderbird that has been proven on the dyno to be among the best out there.   I would think pairing the tubes similar to the FPA would be my choice if I were to build a set of Tri-Y headers from scratch.   Joe-JDC By Litshoot - Last Month Nice engine, im back and forth on the Mummert intake because i don't make smart decisions. the headers in picture are fpa? they aren't tri y but possibly step tube. By Ted - Last Month Here are some links to previous conversations on this forum regarding Tri-Y headers and header design in general.  These are backed up with actual dyno testing which should provide you some additional information. http://forums.y-blocksforever.com/FindPost128280.aspx  http://forums.y-blocksforever.com/FindPost99070.aspx  http://forums.y-blocksforever.com/FindPost55539.aspx  By Joe-JDC - Last Month Yes, they are FPA Thunderbird headers.  We made 613.3hp with these headers on my 375Y engine that was freshened after EMC.  They are stepped 1 5/8"-1 3/4" four into one.  I showed you the picture so that you could see both sides and which tubes were routed into the collector together.   By miker - Last Month I’ve got a set of FPA’s on my bird. I knew they were good, both from my results and the numbers Ted published. But Joe’s numbers are really impressive. I had a friend who built a lot of headers, and did a number of 4 tubes into firing specific tri-Y’s. He cut a decent set of 4 tubes for me and made them a tri y. You could really feel the mid range improve. It wasn’t a Yblock, but it was a pretty healthy 400 cid small block. So I’m a believer in those too, especially for the street. By Litshoot - Last Month fpa could be nice, but i have a 57 ranchero so would probably need to modify crossmember and use motor plates. the only full length headers ive heard that fit well are early f100 fender headers leading to me making a set and bouncing between tri-y and 4-1, in school got to a 3" long extension between 1st and 2nd y bumped hp peak 15% with no losses in an early 2000s cup motor they've been stuck in my head. Ted (2/19/2025) Here are some links to previous conversations on this forum regarding Tri-Y headers and header design in general.  These are backed up with actual dyno testing which should provide you some additional information. http://forums.y-blocksforever.com/FindPost128280.aspx  http://forums.y-blocksforever.com/FindPost99070.aspx  http://forums.y-blocksforever.com/FindPost55539.aspx     I appreciate the recommended posts you often include. theyre always informative, and your search skills are than mine. I'm not sure if ive seen the first thread, but have spent a lot of time on comparison articles and reading through the 11 pages a couple of times. fresh look this time i realized the jardine tri y that tested well pair 1+3,2+4, 5+6,7+8. making it 135° apart. out of curiosity the jardine 1.625 made more hp with essentially a reverse cone at header flange.do you think or test if the 1.75 would benefit from reverse cone or would harm torque.    By Ted - Last Month Litshoot (2/20/2025) ... Fresh look this time.  I realized the Jardine Tri-Y that tested well paired 1+3,2+4, 5+6,7+8. making it 135° apart. Out of curiosity, the Jardine 1.625 made more hp with essentially a reverse cone at header flange.  Do you think or test if the 1.75 would benefit from reverse cone or would harm torque. The key to making a firing order specific set of Tri-Y headers for the Y is to keep cylinders 8 & 6 on the left bank and 2 & 1 on the right bank separated.  The 'Unequal Length By Design' headers takes this to the next level in attempting to get to the 180° design without the crossover tubes. Two different sets of Jardine headers were tested.  One set was with 1½” tubes and the other set was 1¾” tubes.  The 1¾” tubed set did outperform the 1½” tubed set when looking at the scores but the tri-y design made for some interesting number swapping in the HP/TQ values.  The torque values for both sets were good, but the larger tubes actually made for a higher peak torque value than the smaller tubed version.  That was opposite of what you normally see with the 4-1 headers where smaller tubes typically make for higher torque values.  The conundrum with the torque values could potentially be due to the tube lengths being on the short side due to '55-'56 Ford car chassis constraints.  There's no end to the number of variables that would need to be tested to get a solid handle on what works the best. The merge collectors are typically most effective with longer tube headers so it’s hard to say what the effect would be with the shorter header designs without some serious testing.  The rest of the exhaust system is also a player so that must also be taken into account.  The 1¾” – 1 7/8” stepped headers used in the EMC competition had a 3½” to 3” merge collector and when combined with the 3½” inlet/outlet mufflers, made better power numbers with the mufflers in place versus without the mufflers.  The rules that particular year required mufflers and the headers were designed around that requirement. Here's the link to the article that was published in ‘The Y-Block Magazine’.  This article includes additional header tests beyond what was posted previously on this site. Ford Y-Block Exhaust Testing – Eaton Balancing