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This is all outdated, as I have currently installed headers and a 2.25" dual system with 24" glasspacks, which is actually responsibly quiet.
My truck had an exhaust leak at the manifold becuase the heatbox for the carburetor was completely cracked. And, the factory manifold design sucks for making power. Plus, my old system just ended under the cab, and had a tendency to gas you while you were sitting idle. So, I decided to fix it ("fix it" being a euphemism for "upgrade").
The hot tip on these older 300 Fords is to use a set of dual outlet manifolds from an 87-96 EFI engine. They have to be modified, but not much, and are an excellent alternative to a set of headers. Altough headers ultimately have more power-producing potential, the EFI manifolds are much cheaper and will last a long time.
After my manifolds, I constructed a true dual 2" exhaust system. I used a bunch of parts from various merchants that you can see in the picture at the top of the page. It is not mandrel-bent, but it still flows immensely better than the factory manifold and single 2" pipe. I currently have no mufflers, although sometime soon, I will probably pick up a pair of Dynomax glasspacks. It sounds great at idle; it actually lopes. As the revs climb, it still sounds good, but it is so loud that I feel bad driving around after people have gotten into bed......
"What about POWER?" you may be thinking..... before, the 300 would hardly pull itself to 3500 rpm -- now it will happily go to 5000, and I let off at that speed simply because I was afraid I would see a pushrod going through the hood! I know my butt-o-meter is not precisely calibrated, but I have worked on and modified many vehicles, and I would say that this exhaust system gave me an honest 20 horsepower.
Here is my engine with the carb removed, so you can see where I started:
And here it is naked, after the removal of the intake and exhaust manifolds (which was easier than you could imagine):
Since I had everything apart, I took this picture to show a comparison of all of the manifolds: (top to bottom - intake, old exhaust, new exhaust)
Note in the above picture that the factory exhaust manifold (middle) is just a log, and very obviously restrictive compared to the smoothly designed dual outlet manifolds at the bottom.
There are a few things to take into account for this installation, particularly if you are using the factory 1-barrel intake, as I did (for now). There is no provision to connect the exhaust manifolds to the intake heatbox, so the air going through the carb will be cooler, which is good for performance, but bad for carb icing in mid-30 degree weather. Also, this (combined with the freer-flowing exhaust) will make you run slightly lean. And, if your engine had an EGR system (as mine did), it will have to be blocked off, because it is designed to pull the exhaust gas through the heatbox, which is now open to the air, and therefore would be equivalent to a vacuum leak. You can either make an EGR blockoff plate or find a carb spacer from a non-EGR truck which covers the transfer hole in the intake (which I did a long time ago).
For the most part, you will have to do a little cutting to make these exhaust manifolds work with any intake. For fitment with the factory intake, I had to cut off one bolt hole (unused for this app) and a knob on one of the runners. Actually, both of the cuts involved the number four cylinder. Also, there is a tube coming from the rear manifold for the EGR system. Some people remove the tube and put a cap over the threaded connection, but I just cut it short, pounded the end flat, bent it over on itself and crimped it shut with vise-grips. These pictures show before and after cutting, and also how I fixed the EGR pipe:
Note the cut mounting hole and also the silver spot where I had to cut off a protrusion. Some people use a grinder to do all of this, but our grinder cost under $30 and is only about 1/4 horsepower...... I used a sawzall and a metal blade, and it only took about two minutes. Various intake manifolds may require different things, but I would say that the cutting I did is fairly representative of what would be required of any setup.
Reinstallation of the manifolds was fairly straightforward, although I had to try a few different ways to juggle the three of them into position. First, get a good intake/exhaust gasket set. For the actuall install, what worked best for me was to line up the front exhaust and intake manifolds, slide the intake over the locating dowel at the front end and install a bolt in its rearmost hole, and then get the front exhaust manifold's position exact, finally installing all of the bolts that hold them together and to the engine. Then, work the rear manifold into position and bolt it down. Tighten all of the bolts to 26 ft-lbs, and you're good to go. I had to severely push the alternator heat shield forward for manifold clearance, but it went. After I had everything bolted together (with no exhaust system), I drove it around for quite awhile, just because..... It blew pretty good flames out of the pipes when you let off the gas. Here is what that stage looked like (although I did have an airfilter on while I was driving):
Finally, I put all of my parts to good use and constructed the exhaust system. It was tight coming out of the engine area as you can see here:
Everything is tucked up between the framerails nicely, and the pipe that exits on the driver's side goes back on the passenger side of the transmission, then crosses under the very front of the driveshaft. Here are some shots showing what it looks like underneath:
Here you can see my right side tailpipe coming out at a 45 degree angle in front of the rear wheel:
Final installation notes: To make the elbow coming out of the front exhaust manifold fit, I had to "clearance" the inner right fender, which meant beating with a small sledgehammer, cutting a small hole so it could go over the top of the shock absorber, and also pulling and twisting from in the wheelwhell with vise-grips. If you use factory headpipes or have a custom bent exhaust made, that probably would not matter. Here is a shot where you can see that my inner fender is modified so that it will pull across the shock absorber stud:
Also, if your exhaust pipes are routed anything like mine, your starter cable will be rubbing on them, which is bad. For me, the fix was a longer, rerouted cable. I went straight up from the starter to the bundle of wires on the firewall, and then back to the starter relay. Thankfully, I already had incentive to replace the cable since I basically burned the insulation off of the old one while driving around with open manifolds and blowing violent flames right at it..... The last thing that I can think of is possible interference with lines for an Evaporative Emission Control system. My exhaust pipes rub on the line coming up to the charcoal canister, and I didn't feel that would be prudent. (As far as that goes, I never have thought that having a canister full of gas fumes was a good idea.....) So, underneath the front of the bed, there was a hardline from the tank with a rubber hose coming off of it which went forward. I disconnected the rubber hose, bent and crimped the hardline with vise-grips and use a vented gas cap instead of a non-vented one. That is all I can think of. If this seems a little technical now, it will make sense when you actually are doing the process.
email-> ben@wantlandracing.com
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