My thinking is that headers make more power through the resonant tuning on overlap more than the dry air flow. It will be interesting to see some flow numbers on the end runners/ports.
I built a 408 stroker, aluminum head, high comp, tight quench. I ran port matched, enlarged exit magnum truck manifolds. After a year I built long tube 1 3/4" to 1 7/8" step headers, fenderwell exit with 2 1/2" to 3" merge collectors. I also set the primary tubes into the collectors in proper firing order. I picked up 5 tenths and 9 mph. However the best improvement I realized was no more detonation or pinging. With the manifolds I needed race gas for full throttle running, it was fine at any other driving. With the headers I have no problems on 93 pump under any conditions. That was an unexpected surprise which made the ridiculous time I spent building them pay for itself. I'm thinking the better scavenging may evacuate my cylinders better, reducing combustion chamber temp and intake charge dilution. Funny thing is I wasn't going to switch except the iron manifolds were too close to my steering box and frame (mopar in a Ford). But again Charles, thank you for all your time and work you let us see. Bobby O'
In reality it reads like the engine needed a different lobe center angle for manifolds than headers due to their poor flow and lack of tuning. Good info. Thanks
CarCraft put headers on a Dakota RT (magnum 360) when they first came out and the OEM manifolds on it worked just as good, almost no gains with the header.
Thanks Charlie , HP big block manifolds in the muscle car era out flowed most tubed headers. The biggest draw back is weight with those factory cast iron manifolds.
what I never understand was as long as 272 - 318 have been around just like the 340-360 have. they have diffent sized exhaust ports and 99% of headers are designed to fit the ports of 340/360 . you would think they would come out with 273-318 port headers . Not to mention the future exhaust leaks due to 2 diffent sized ports on manifolds and headers and gaskets . thats why I match up 318 manifolds with 318 exhaust gaskets so there are not future burn through on the gaskets
Nice! It looks like you are measuring the flow resistance (head loss) of the header tube. To be closer, a 1 5/8 exhaust pipe could be added to the manifold roughly the length of the effective header tube. This would more evenly compare the two and then see the difference between the "plenum" manifold with the transition losses vs the header.
@@servediocylinderheads I was referring to hooking it to the exhaust collector (2.25"?) and make a single port exhaust pipe to mimic the tube length of the header.
I'm not surprised at your flow results. The induced drag losses in the longer pipe are being measured on the header, but not for the manifold. That said, the header doesn't start to come into play until you have pulsed flow. I have dyno'd many cars before and after exhaust system changes. Not once have I ever seen the mythical 20% gain used in advertising. Often there was absolutely no discernible gains that could be measured, but that was on standard, or near standard engines. Personally, I think that the most important part of the induction cycle is valve overlap, as it starts the entire procession of intake charge movement. As such, the exhaust dynamics are absolutely critical if you are trying to obtain the maximum out of what you have. Going from one not so good set-up to another not so good set-up will show no benefit. However, going from a not so good set-up to a more good set-up will result in measurable gains.
@@servediocylinderheads yeah but can you guys use early 340 manifolds if that gets you where you need to be? I think they repop them maybe 800 dollars a pair.
I think it's time to drop the "mission impossible" tag, considering how far this project has now drifted off it's original concept. and how Tony ( who coined the "mission Impossible" tag ) has decided to distance himself from it. May as well just call it the Vizard, Unity Motorsport 318 project. I enjoy the cylinder head and manifold information you have provided and will continue to watch it , but I won't be bothering with the rest of the build because it's just turned into another Magazine style build and I don't really see anything "impossible" about it any more, and that's a real shame.
New name ? I'll leave that up to the powers that be :) But I will say that your series of Cylinder head and manifold videos are excellent and stand on their own merits, regardless of where the 318 ends up or if it even gets completed. My opinion is that if you hadn't been so enthusiastic about this, and kept it relevant through your hard work, then this project would have faded away long ago . And lets also not forget one other benefit from all this.. You and Rob meeting, and the friendship that followed. I know Rob from ABodies and he is usually the voice of reason, in a forum that's threads usually devolved onto a dumpster fire :) LOL..
@@user-ky3xu8dx2i Rob rules! I guess a new project name has not been choosen. I begged to be part of this project. Which consisted of me asking David if I could be involved and he said, "Yes!" Right away. I never liked that the 318 is the red headed step child who gets no respect. Super glad to be a part of this project. Thanks!
