When building a set of tri-y- headers are there certain cylinders paired up or just whatever is handy ? I assume all the pairing should be the exact same length ,but what about the primary length vrs the length after the first merge. Just thinking of trying this on a set of fenderwells . Thanks fellas.
Check out post #105 on the thread bellow. @joel made a killer set of tri-y type fender well headers for his 40. this might give you some ideas. http://www.jalopyjournal.com/forum/...ivor-40-coupe-build-fired-it-up.944754/page-4
On a small block I always pair 3&7amd 1&3 then 2&4 and 6&8 on the other bank. Pairing depends on your firing order and while my pairing is not exact it is the best easy option. Obviously in a perfect world you would want to pair them 180 out, but that probably isn't going to happen on a V-8. The old guys used to say that your primaries were important and you could let your secondaries run wild. But these days guys like @hotroddon are designing them a lot closer than that. By the way he is a good one to contact for advise.
A great read on exhaust technology is "Scientific Design of Exhaust and Intake Systems" by Philip H Smith and John C Morrison. Opened my eyes. Oh , dont be scared by the math. Just learn the theory on the systems. Oldmics
Unless you plan to build a number of sets and dyno for the best results, Packageing and fit for me is the top priority,
I remember reading every single "header shootout" in every car magazine, for about 30-straight-years. Unless your car has no chassis, suspension steering, or anything else around the engine, you will run smack into something that forces a design change, that will likely negate any performance gains. True sequential scavenging headers have been done, but they have obvious issues. Try-Y headers work toward this scavenging goal. They cannot get quite there, as they can't easily pair with cylinders on the other side of the engine.
When Doing Tri Y's for a street car, you want to pair cylinders that are Not next in line in the firing order. The separation of firing is what makes them scavenge well. In the early days when Doug came up with the first Tri Y's and Carroll Shelby adopted them for the GT350's the primaries were pretty short (8" was not uncommon) and the secondaries were long. I still do some design's that way, but more and more I am lengthening the primary out to the 20" range and still keeping the secondary as long as it will package in the car. We used to think that the primary length was the most important but we now realize that secondary length will affect the width of the power band greatly, so I work with both to achieve my goals. I recently did a back to back on a ZR-1 Corvette. First I optimized a 4-1 design and tuned the EFI to match and then a 4-2-1 (Tri Y). Up to 4,000 rpm the 4-2-1 made more TQ and HP than the 4-1, 59 ft lbs (and 29 HP) more at 2700! From 4,000 rpm on, they were pretty much even, both topping out at 412 ft lbs and 441 HP at the wheels compared to 350 and 377 with the stock factory headers. Due to the tunnel in these cars it is tough to really get enough length overall, but I was pretty pleased with the outcome.
I'd love a set of true equal-length tri-y headers for my Falcon-6, but they seem to only exist in Australia, are not cheap, and will cost a fortune to ship, if they might arrive intact.
Thanks guys ,I thought it might be easier because of the fenderwell and having a little more room.Is there any difference in the way the collector is done?
Easier is relative, but making mine was one of the most enjoyable parts of the build. I used 1 3/4 primary tube and 2 in. sceondary tube merged into a 3 in. collector. As Beaner said, my controlling design parameter was fitmit and packaging. I went out to get some idea of lengths. The longest primary was #1 & 2 cyls 12/14 in, shortest primary was #4 & 5 @8/9 in.The remaining primaries were in between. The secondarys are about 20 in. On the drivers side I paired #3 & 7 together and # 1 & 5 together.
YES - a merge style will make the most power and MOST people end up putting too large of a collector on!
Tri-Y headers on a Pontiac V8, firing order 18436572. 1.75" primaries, 2" secondaries and 2.5" collectors.
Tri-y's are definatly the best street header system but work just fine in competition. The photo shows mine for my GMC 6 with the 7 port stock cylinder head which is more difficult to design when 2 of the exhaust ports share 2 cylinders. These are a double merge style. Before the start of the cone the last merge ends with a 2-1/2" diameter. The max my engine sees in high gear is close to 6000 and I can guarantee it works. For you guys on another thread about engine stands for GMC's, this is a cheapo HF with a 1"x2" board at the front of the pan.
you're right and I stand corrected. I need to use the quote function more because memory just ain't getting it done.
He's probably talking to me, but my relatives on the Isthmus call me "Frijolin" so I guess the shoe fits. I think you and Don spoke more about packaging than I did though.
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