What sort of improvement in gas mileage should I expect after fitting headers to my 390 pickup. I'm trying to increase the range because at the moment it's ĺike my Norton motorcycle, you can't pass a gas station without stopping

 

I wouldn't say its considerable, if you want gas mileage fuel tuning, distributor curve and speed are the biggest ones to look at.

 

Not considerable, but well worth it. ANYTHING is better than the box manifolds Ford cursed them with .

 

On my 65 with the 390, column w/ O.D. and headers, PO installed long-tube headers and I believe they are Hedman, and the best I can get is around 11-12 mpg highway? I do have 4bbl set up but rarely if ever do I get the rpm into the carb secondaries? Also, an issue with the headers on my 65 is the flange that connects to the exhaust set up meet at the engine cross-member leaving little clearance, severe terrain the flange can strike the member., same issue with the other 65 w/ long-tubes. If it came time to replace them I would do some research on the possibility of Shorties, or have a shop/DIY and cut before the flange and add an extension. Anyhow, food for thought?

PS/ in the process of replacing radiator and cab supports which are shot which may increase the clearance on my 65 w/ the 390?

 

My highboy with a 360, I put long-tube headers on. Oh my... what an improvement in throttle response, and just generally getting the truck moving (4.10 gears).

 

New motor and transmission mounts would also help some, especially if they're old and soft now. I think FPA listed shortys for a pickup, they're not cheap, but they're high quality

 

Agree, don't believe the trans or engine mounts are that expensive nor labor intensive to replace; with regards to my 65, I will have to do some research, the engine is out of 64 Thunderbird and the motor mounts do not appear same or similar to the engine mounts for the truck application??

 

Motor mounts changed in '65. You may have "adapted " mounts. I will look up more on this later if someone else doesn't beat me to it.

Edit: 2 bolts up to '64, 4 bolts '65 and later.

Post 5:
https://www.ford-trucks.com/forums/8...onversion.html

Probably pretty easy to convert or adapt.

 

Not to Hi-Jack the thread although info may be helpful to fellow members; I will take and post photo of the mounts when time permits.

 

Yep. Also, make sure to use vacuum advance. That's free mileage, and can help lower coolant temps in a marginal situation. I can give more specific tips on how to setup your ignition advance curve for mileage if you want.

 

Don't expect any fuel mileage gains from headers. I gained 1 MPG on the highway by switching from the four blade rigid fan to a flex fan. I eventually went to an electric fan. A drop in electronic ignition would also help if you're still running points

 

Seems like a million years ago, but I had a 1966 Ford Fairlane 390 GT. I pulled that engine and installed a 427 single four barrel holly 600 cfm carb. One day I left Riverside Calif for Long Beach Ca. and never touched the gas pedal I had adjusted the carb for about 1000 rpms at idle. I would slip the clutch at stop signs and stop lights to get it going in first gear, then without touching the gas pedal, I would shift to the next gear.
Boy was that a long drive. I did get 18 something mpg, can't remember exactly. I would never do that again plus now days, the traffic is so congested, I would probably get shot going that slow.
My point to the story is we are never going to get good mpg with our FE's About 12 mpg is all you can expect driving normally. I have had 352's, 360's, 390's 406's 428's and 427's and none of them got much better than 12 mpg and some were a lot worse, depending on the vehicle. Headers does increase your horsepower and engine efficiency. On one of our 427 engines it increase the hp by 45 hp. on the dyno with no other changes. And that was going from a free flowing cast iron stock 427 factory header to Hooker steel headers. The stock log type exhaust manifolds are horrible if you want power.
Extremely restrictive.

 

Everything you said here is true. I too had a 427 but in a 67 FB Stang. One trip to Baton Rouge and back it pulled down 18 mpg by keeping my foot out if the carbs.(yea, carbs) Otherwise in my 70 F100 pickup , the GT390 out of the Stang averaged 10-12 mpg, no matter what I did. This motor was rebuilt with TRW 30 over pistons, Cam Dynamics cam with something like a 296* adv duration and .516 lift. Heads were the stock 67 GT 390's, intake was a 428PI topped with a 750 Holley VS carb, Headers were by Blackjack. I had Hookers on the 427 at first but then when I pulled it due to a wrist pin coming loose, replaced them with 428CJ manifolds. Never dynoed it but it did loose some topend HP with the CJ's

 

A 427 in a 67 Mustang would be a very fun ride. We had a 1970 Mustang Mach 1 with a 428scj back in the day. I sold it when I got married, "big mistake". Not getting married, but selling the car. LOL...

 

Yea the things we do when there's bills to pay, needs to be met, when married. I sold that Stang in 1989 to get the money for a down payment on a new 89 Ranger, Needed that cause the 70 F100 was eating my lunch driving 60 miles (round trip) to work everyday. And get this, I sold it for $3000............ But ten years later the bug bit me again and I pulled the V6 out of the Ranger and put the first of 5-302 based engines in it. Including the 331 TriPower that's in my 77 Comet today.