I have an 86 E150 4.9 6cyl, 4spd and because of some leaking exhaust gaskets, I have to take the tangled pair of mainfolds off to change the gaskets... both the intake and exhaust, from the block.

Since I'm going through all the work, and will probably have to have the one machined smooth again, I'm wondering (this is a long-distance, main-truck vehicle for me) what kind of upgrades I could replace that I'm taking off with.

I see Ebay has some Holley brand intake manifolds, and I know headers are supposed to have less resistance. I don't care about power (1bbl carb) I care about mileage. Would a heat bandage wrapped exhaust manifold make much of a difference? Are the Holley intakes more for bigger carb setups, to turn out more power, or would there be an efficiency benefit to this too?

I'm all about the durability, dependability, and good gas mileage (I dont work the truck, just use it as comfortable long distance transportation with room in the back if I need it) so please keep that in mind when you're evaluating the options you want to suggest.... I'm not so much concerned about the cost of the upgrades as I am the difference they'd make, since this truck is used that much and that important to me. Plus, I'll be owning and driving it for a good long while.

Thanks!

 

The efi exhaust manifolds are supposed to be a good inexpensive upgrade, but I'm not sure if they clear the alternator bracket. As far as the intake, I believe the main reason people change them out is because the four barrels will not bolt up to them. Was the intake manifold that you are referring to for the one barrel?

 

If your ignition has points, the DUI distributors are supposed to add about 4mpg and 10-20 HP.

 

Yes. Same question. What year of EFI 300 of exhaust manifolds or even what is a cheap/decent upgrade from the stock exhaust? What are people doing to the older 300s? I don't have to do emissions here given the age of the machine, so cat can go. still want some back pressure though.

 

"...still want some back pressure though." Why?

BTW, the 'needs back pressure' myth was debunked way back in the last century...but for some inexplicable excuse it still seems to live on.

 

sweet.
but, for a little baby 300. sup with exhaust?

 

A lot of people opt to use EFI exhaust manifolds instead of headers. They flow pretty well and headers are only marginally better. With headers, though, you need to ceramic coat them or if you're on a budget header wrap them or it will cause severe carburetion issues, affecting performance, reliability, and fuel economy.

Back pressure is a myth. Don't worry about it. EFI manifolds to true dual 2 1/4" pipes increases power by just under 20%, depending on your setup.

A DUI distributor adds a few miles per gallon and about 15hp. For $350, I'd do it. I am doing it, actually. Soon enough.

As for intake, your single barrel carburetor is about as good as it gets. I would and am personally adding a Holley 350cfm 2bbl with the Offenhauser single plane intake manifold. I doubt it'll take away much fuel economy at all. A lot of it is proper carburetor tuning.

 

That's what I'm probably going to do, just rebuild the stock carb. The whole engine is being pulled and swapped with a rebuilt 6 this weekend. Figured while I was around there might as well do something because the whole thing is old..

I used to run 12.5 @ 108 on NA 5.0EFI. daily driver. hooker headers, H pipe, flowmasters, dump. Just a straight pipe would have frik'n bogged.

I saw the DUI dist. Looks sexy.. Just looking to clean up the exhaust from the 79 setup that's in there now. My goal isn't HP, just something newer'ish.

 

Plus back pressure makes a massive difference on my harley48 1200 DPI.
Maybe that's diffrt though. Do have to tune.

 

pretty much any ford 300 EFI exhaust manifold will work eh? looking for parts now

 

Back pressure is and always will be a myth. What you are calling a loss of back pressure is actually an improperly tuned exhaust that can't scavenge anything.

That, or you're running straight pipes but not tuning the engine for the leaner mixture. Richer mixtures give you bogging, like you said.

 

"... scavenge..." That is a most important term. Scavenging is desirable, back pressure is not. Motorcycle tuning is in a much different world than a 240/300 Ford I6.