Edelbrock Pro-Flo Multi Point EFI System #3509

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Part II: Our Exhausting Saga Continues...

New 3" Single Exhaust System

From the Passenger Side

From the Driver's Side


Passenger Side Downpipe

Driver's Side Downpipe

3 1/2" Chrome Turndown

Low Angle Rear View

3 1/2" Chrome Turndown

Sounds Authoritative!

One of the first things I needed to do for this EFI install was replace the exhaust system. The old exhaust was a dual 2" system, and it was cooked to death. It was devised by Jim Black and his exhaust guy. Initially, Jim had wanted to install a long system that took the pipes forward through a set of glasspacks, then back through a set of mufflers. Unfortunately, the Transit has a massive transverse steel beam just forward of the engine that precluded running the pipes forward. The dual system (with crossover pipe) was a decent compromise, and was a nice improvement over the initial system.

Pity I didn't get a picture of the old system before it was removed. It only had about 10-12,000 miles on it, but it was shot. The folded and pressed mufflers had badly overheated and were "oilcanned." The innards were pretty much gone, too.

I thought I wanted the new system to be made of stainless steel. It turns out that stainless' main advantage over 'regular' steel is rust-out from short trips: condensation not getting baked out. Well, things not getting hot enough is not one of our problems! So for this system, stainless would just be extra expense.

I had imagined the new system would be much like the old one, albeit with better components (e.g., welded mufflers instead of folded/pressed ones, etc.). After discussing things with my exhaust guy (Scott Starck at Collins Muffler in Loveland, Colorado - "Family Owned Since 1958"), we decided on a 3-inch diameter single exhaust system instead. Current practice favors large single systems over duals. A single 3-inch exhaust system has a 12% greater area than a dual 2-inch system, while having 25% less wall surface area (less friction w/ the pipe wall).

The new system has the driver's side downpipe crossing under the engine and joining the passenger side downpipe into a single 3" pipe. This 3" pipe continues toward the passenger side of the bus, where it makes a 180 degree turn - using two mandrel bent aluminized quarter bends with full diameter all the way 'round. The pipe then crosses back under the engine and into a single 3" IMCO aluminized, welded steel muffler, where it exits straight out the driver's side through a 3-1/2" chrome turndown - rotated 45 degrees to the rear so that it doesn't point straight down to the ground and stir up the dust (too much, at least).

The idea is that both the 3" pipe and the longer 3" muffler are more free flowing than the dual 2" system. There will be less heat buildup in the muffler, in particular. Scott assures me that coupled with the longer exhaust path, this free flowing muffler should last "forever."

There are some items of note in the pictures. Notice the nicely crafted downpipes that curve to the rear. Each one has and oxygen (O2) sensor bung welded in. The passenger side O2 sensor is for a air/fuel mixture display; the driver's side sensor is for the new closed loop EFI system. The 3" outlet pipe from the muffler extends almost all the way through the chrome turndown, which should help keep it from discoloring so much from the heat.

Please don't pay attention to the oil and grease seemingly all over everything. The engine leaked quite a bit before it was rebuilt, and it's not much better now (Update: the major oil leak was caused by the engine rebuilder having folded a lip of the front main seal while installing the harmonic balancer. That has been fixed, and the engine no longer leaks). The chrome Moroso valve covers are being replaced with cast aluminum Mopar Performance Parts valve covers - hopefully that will slow down some of the leaks (Update: the passenger side Mopar valve cover worked fine, but the sealing surface on the driver's side head wasn't flat enough to work with those stiff covers. That side now has a Moroso anodized stamped aluminum cover that seals nicely). I'm getting the engine degreaser out tomorrow, in preparation for installing the new EFI system.

Stay tuned for Part III...

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