I've gone over the mods i did to my exhaust and talked about the gains i was rewarded with but now i must discuss the exhaust again and why it is so important on the SBF. The SBF is well documented to have smallish valves and weak, poor flowing exhaust ports, anything you can do to improve velocity through the exhaust port is money well spent.
Replacing the factory muffler with a low restriction Walker Megaflow was step 1, then i removed the secondary cat converter and replaced all the pipe from the back of the pre-cat through the 2.5" muffler with 2.5" pipe and retained the single exhaust, the difference was night and day and still puts a smile on my face when i roll on the throttle to pass another vehicle or climb the steep grade on 26 coming out of Portland headed westbound, it pulls now where before it would fall on its face and laugh at me.
There are more gains to be had with the exhaust system, i can almost guarantee that especially now that i know just how restrictive the factory exhaust port really is, long-tubes would be one of the best things you can do for the SBF with stock heads, full length hedders will drastically improve the scavenging and give the SBF the help it really needs on the exhaust side but in light of my new discovery i think a set of hedders are in my future plans for the van, aftermarket heads would be great but for monetary reasons i don't see that happening, what i do see happening is replacing the camshaft with the Crane 444232, the camshaft in the 351W is terribly small especially in the later models such as mine, adding 1.72 ratio full rollers will bump the lift to just under .500" and add just a bit more duration for good measure, i can't wait

 

When I had the Crane cammed 5.8 in my F150 with longtubes and a 2.5" single exhaust system it would climb the hills on the Trans Canada through New Brunswick(similar to I81 through Pennsylvania) with cruise set at 70mph without dropping out of OD or losing any speed.

 

Going to follow your advice and keep the single exhaust, draw the hedders together with a y-pipe and tie it in with the existing system, cheers..

 

Yeah there is no benefit to duals on these trucks because of the midship fuel tank.. both pipes have to run down the pass side anyway. Magnaflow makes a nice 2 into 1 collector and various U and J mendrel bends that can be cut up to create the 2 into 1 system, I have built a couple systems like this for my trucks.

 

I would have to assume that since the truck chassis is shared with the van and the hedders for both the van and truck would be similar in design (big leap of faith) and praying the collectors end up in the same place (another leap) then a similar setup as to what you built would fit my van chassis, yes ?
This will be perfect opportunity to relocate the 02 as i really don't care for the idea of mounting the 02 inside a balance pipe as the factory has chosen to do..

 

The van frame is actually a little wider than the pickup so there will be a little more room under there, and they don't make van specific headers but it's the exact same powertrain as in the pickups so it's not a problem. The stock O2 location works well enough, at the proximity to the engine exhaust pressure is still pretty high so the sensor sees what it needs, There is no need for it to see both sides of the motor either since there is only one fuel map for all of the injectors and they are fired in batches with 2 injectors on each side of the motor in each batch, so installing the O2 in the passenger side header collector delivers the same results. I have played with dual sensors on my truck since it has a Mustang computer with dual sensor inputs, but there was no difference in the left and right bank fuel maps with 2 sensors which makes sense if all injectors are in good condition so I put it back to a single sensor. The motor has consistently delivered better than average fuel milage with that setup too with an average of 13mpg US and a high of close to 20mpg at steady highway cruise.

 

Actually they do make van specific hedders, Hooker 6910's are listed up to 1990 and since my van is a 1992 i emailed a few people and was told there was no reason they would not fit since the chassis did not change compared with the 1990. Agreed, no sense in dual sensors but i still like the idea of the 02 being in the actual exhaust flow and operating at the correct temperature, it sucks to be a Virgo because everything has to be perfect even something as simple as a sandwich, probably a touch of OCD there too

 

The O2 sensors on these trucks are heated so there is no issue with that but I agree it should be in the exhaust stream.

 

There is a difference in chassis room with the van vs a pickup. I had a dual pipe setup off a 97 F250 that I was going to use under my 96 E150 van. It didn't fit the van at all, so I'd keep in mind that full length headers for a pickup might not fit under a van. The shorty headers do interchange though.

 

If i pull the stock manifolds it's all or nothing and going with long tubes, there is no advantage to shorty hedders in this scenario..

 

That's your choice. Pickup long tubes ain't likely to fit a van. I went with Pacesetter coated shorty's in my 96 E150. No regrets there. They're well built with nice thick flanges, I used Summit's copper gaskets between them and the heads, zero leaks, the bolts have not loosened after 7000 miles. As for whether they flow, I can tell you this: after installing the headers with the full 3" system, I had a few pin hole leaks in the joints of the Y pipe that could be felt by placing your fingers near the pipe, so the flow is there, enough so to cause enough backpressure to feel the leaks and confuse the downstream O2 sensor, with 3" single system behind the Y pipe.

 

That's why i'm ordering a pair of Hooker Comp 6910's for $212, they are listed for the 1990 E150 with 351W..