Just an update on this. I swapped the PF4s single plane manifold for a Mercruiser MPI Dual Plane using the rest of the PF4 system and installed old TH315Y Thorley Tri-Ys and put a mandrel bent dual 2.5" exhaust on this. I have been driving it since last week daily. Runs very strong for what it is. Actually had it pull down a 5
9s 0-60 on my GPS performance app which is fairly accurate. Stall the stock converter a bit, walk it off the line and send it and it moves pretty darn good. 60 mph is about 5,600 rpm in 1st gear. With the GM 6492 roller cam, 1.6 full roller rockers, aftermarket vortecs thw dual plane, 4bbl throttle body, tri-ys and 2.5" free flowing exhaust this little 350 happily and easily rwvs to the 5,800 rpm rev limiter. It does not really fall off up stairs just pulls.
0-60 PF4 Data screen capture with audio
https://youtu.be/UjEKGehu1M8?si=vv7HNWoAbrkuwYSU
~60-65 mph cruise with a 3-2 kickdown and acceleration to ~85 mph
https://youtu.be/BjKfFEwvVKA?si=RqVgVX5j0vO_-Qyi
What it sounds like with the headers, dual 2.5" mandrel bent exhaust using the dual in/dual out magnaflow built turbo muffler. Unkowingly the tail pipes were welded up with a chunk of shreded brake lathe silincer band inside one of the, they had been laying around my friends muffler shop for years before we cut them up and made the fit. XP5033/XP5034 tailpipes for a GM A-Body modified to fit the van.
https://youtube.com/shorts/AP9oFP9kM...luyWGMnH-6m_AD
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