Does anyone know how I can get better MPG out of my 390? I am getting on average 8 mpg. I'd like to up that if possible. Would a new ignition help? If so what parts and brand? Everything on my motor is stock except for the K&N air filter I am waiting to put on. I am running dual exhaust. Has anyone gotten good resutls out of their attempt on getting better fuel consumption?
The only problem with that thread, is that they pretty much say that your screwed for mileage. You can get 14-15 mpg on a 390, almost double what you are getting now (thats what mine was at in my 250). Put in a good free flowing exhaust system, good intake/carb choice, good ignition (I prefer MSD),and make sure your tire size and gearing matches your driving range and you'll get all the milage you want. Sure all that stuff costs bucks, but if you can double your mileage at todays gas prices it will pay for itself in time.
If your knuckles ain't bleeding you did something wrong.
'72 F-250 "Hi-Boy" 4x4, Dana 60/HD44, FE390 @ 400hp(purt near!), 4-speed, custom suspension w 4" lift, mud on black.
Like you I was getting NO mileage. I took off the stock Holley and put on a factory reman Edelbrock #1405, Vacuum secondaries and a manual choke. Everything improved dramatically,,,mileage went up about 3 or4 mpg. No more flooding and leaking, etc. Carb was $325 Cdn or or about $250.00US
Hey thanks for the information. I forgot to mention that I have a Edelbrock 1405 on it. I just put an electric choke on it. I do plan on upgrading my dual exhaust with Flowmasters (40 series) but other things are more important right now. Like a locker and getting my mpg up. The existing exhaust is fairly new, but it doesn't have the right sound I am looking for. As with everybody being on a budget, I am afraid to spend my money on something that claims to work, but doesn't. From what I have read, MSD does sound like it would help. The motor has about 18,000 miles off a rebuild. Everything is fairly new, so I would hate to replace something that is still good. But I may have to. It's that or start driving like an old grannie, but then that goes against my human nature. Although, I will do that if it makes a difference!
If I do replace my ignition, what parts should I replace? Or should I just replace the whole thing?
Jake, okay here are a few ideas. Remove your electric choke, a manual is better for mileage. If your ignition is healthy, you should need the choke for only 90 seconds or so. Ignition- you should be running a duraspark distributer or a points converted to pertronics, and use a vacuum advance hooked up directly to manifold vacuum. Aftermarket distributers are generally a waste of $$. Using your factory dist,spend your extra effort on a computer from Jacobs or MSD. This will allow a nice fat 080 spark, enough to lite the mixture no matter what. Thermostats- run as hot as you can without overheating. Your aluminum pistons have thier lowest coeffiecent of friction in an iron bore at around 235 degrees. Those fellows that like to run cool don't know what they are talking about.The more heat you throw at the radiator, the less there is to drive the pistons up & down the bores. 195 is good, 205 is better. You might want to think about propylene glygol for coolant instead of the regular stuff, PG can take more heat. What year is your truck? what trans do you have?and what are your axle gears? For part 2, what kind of pistons did your engine builder use? DF
You haven't mentioned what your rear end gearing/tire size is. With 31" tires and 3.5 rear I was getting about 11mpg w/ edelbrock 4v (probably jetted rich) aluminum edelbrock intake and dual exhaust through abought 2 1/4 pipe w/ stock exhaust manifolds and cheap turbo mufflers. If you are running 4.11's or something like that, maybe you should consider a higher gear ratio. You also don't say if you have a 9" or Dana rear end. Swapping a 9" isn't too terrible difficult. I'd also suggest you have a knowledgeable person who really knows distributors, check and or recurve your distributor. BTW I just bought and installed flowmaster delta 50 series on my 302 powered truck w/ 2 1/4 duals (different truck) sure sounds cooler than stock Ypipe small single exhaust. I can't report yet on mileage increase. But it makes my 302 sound bigger.
Wow, great information guys. Thank you! My truck is a '76 F150 4x4, 390, NP435, 205 Tcase, Dana 44 up front and a Ford 9" in the rear and currently I am runing 31 inch tires. The gears to my knowledge are stock. So I am guessing they are either 4.10s or 4.11s. I don't know what pistons where used when it was rebuilt. I am going to say stock pistons. I bought it after it had 15,000 miles off the rebuild and since then I have put on 3 thousand in 2 years. I drive it for play, hunting, ect.. but now it will be my daily driver until I can buy a car for the fuel economy.
I do plan on puting 35"s on it soon with a locker in the rear. So my truck will become diversified, 50% on the highway and 50% on dirt.
Yeah those Flowmasters do make it sound a lot cooler. BBT, once you find out if you are getting better fuel consumption, please let me know how it turneds out.
But if I go higher in the gearing, wouldn't that hurt my off road capabilities? How about rejetting the carb or putting new metering rods in? Someone once told me to change the metering rods, but I wasn't sure if I should. What about headers on my soon to fallow exhaust? I was planing to keep the stock manifolds, but who knows? Sorry for so many questions, I just have a lot to learn.
Jake, look and see if there are tags on either of your axles to find out the ratio, I would guess them to be 3.5s which would be good. 4.10s are way too low for any kind of mileage. If your 76 still has its original distributer you can add a Jacobs or MSD to help out. 35 inch tall tires will help as well if they are not too wide. I asked about your pistons because ford was lazy in the mid seventys when they lowered the compression to handle the falling octane of gasoline. Ford built a lot of 390s with leftover 410 mercury pistons especially in the trucks. The pistons they used had such a low pin hieght that combustion efficiency was reduced. The cure, when rebuilding, is to use flattop pistons intended for a 66-70 four barrel car engine, TRW L2291Fs are a good example. Sadly, 9 out of 10 shops build the engine with to low of compression when rebuilding, and some of the fuel economy is lost. The only way to check is to pull the heads off and look, and the only fix is to swap the pistons. The other big problem with rebuilders is that those same 9 out of 10 don't do the oiling system correctly. To check if yours was done, get yourself an extra gasket for the oil filter adapter and remove the adapter and measure the diameter of the oil hole coming from the pump, if it is 3/8s you have some work to do. If it is 7/16s or 1/2 it has been fixed. If it has not been done I would be happy to explain what you must do, it will take an afternoon to fix it, it would have taken the engine shop 15 minutes if they had done when the thing was apart. DF
DF, I will check my tags tomorrow to see what ratio I have. I was always thinking it was 4.10s. Maybe I have been wrong (not unsusal). On the oiling system, how much will it help by making the oil hole bigger? Is it worth the trouble? I read about that once but can't remember where it was. It figures Ford got lazy on the 390 in the mid 70s. From what I have heard, the early 390s are the ones that you want. But I didn't have a choice.
I am no mechanic, and I always get myself into trouble on attempting to fix things. But I am curious about the oiling system. If you do have time, please explain how to increase the hole diameter. I am in the middle cleaning up my shop. Never knew it was so difficult to just clean it out. But if I can't benefit from the oil system job, maybe someone else in my situation can. How difficult is the job? I know the guy who I bought the truck from, so maybe I should ask him. Well I know where he works anyways. I do know this isn't the original engine that the truck came with. It had a 360 but when the guy went to replace it, he put in the 390 for more pulling power. I have no idea where the 390 came from. But I believe the 390 is a '76, but not positive.
This is something I copied from another website, but I cant remember the original author
"And now for the real story about OIL SYSTEM MODS.
We will start with the top oiler 332 thru 428.
First, letís start at the oil pump flange. We will start with a 5/8" dia. drill and open up the hole at the oil pump mtg. flange. Then using a die grinder and a carbide rotary file, we will port the opening (at the) pump (I spoke with Earl about this sentence. He said what you are doing is like a gasket matching. Take the gasket from the oil pump and gasket match the openings).
The next operation is to open the passage to the filter adapter to 1/2", using a 3 fluted core drill (A 2 flute will do, but you better have a good hold on the drill motor).
Moving right along, the next operation would be to check the diagonal hole that runs across the front of the block. It should be 7/16" dia. The drill bit should be flattened on the tips to prevent drilling thru the casting and scraping the block. The same drill should be used for the passage connecting the diagonal passage across the front to the main oil gallery in the center of the lifter valley in the block. The main oil gallery must be opened at least back past the 3rd main bearing oil feed hole and preferably, all the way thru at 7/16" dia (min.), 9/16" preferred.
Next in line would be the passages that go from the main oil gallery to the cam journals on the center 3 cam bearings. With the cam bearings removed, we will use a 5/16" dia. taper length drill thru the oil holes in the main saddles, which are already 5/16". For this operation we will put a flat on the drill point to prevent drilling thru the top of the block and flatten the cutting edge to 0. Rake to prevent the drill from screwing itself into the hole and breaking. This is a good idea for any drill being used for opening up an existing hole. One other bit of prevention would be to take an old main bearing insert and grind off the locator tag. Then placing it in the main saddles, prior to drilling. This would prevent the drill chuck from damaging the main bearing bore. It won't hurt to open up the passages to the front and rear main saddles. However, they only feed one rod each and don't need as much supply as the center three mains do, which feed two rods each.
This would be a good time to tap the lifter offshoots from the main oil gallery with a 3/8"-24 tap. Then a 3/8"-24 set screw can be used to block off oil to the lifter, should a solid lifter can be used, or for easy removal, to go back to hydraulic lifters in the future. The oil hole exit at the main bearing on 1, 2 and4 will need to be chamfered to make the oil hole line up with the hole in the bearings. All of the oil holes that had plugs in them can now be tapped and fitted with pipe plugs and don't forget the one behind the distributor, at the end of the lifter gallery. This is a major cause of low oil pressure after a rebuild."
Who is this Earl ? This set of instructions is way off. 5/8 is too big at the pump flange, should be 1/2. The diagonal to the filter pad should be opened up to 7/16s, the rest of the sizing is okay. Earls instuctions also fail to mention the mismatch between the oil hole and the bearing's hole on mains #1,2,and 4 and does not explain the restriction problem at #5 main. Again, who is this Earl, he sounds scary! DF
[font size="1" color="#FF0000"]LAST EDITED ON 19-Mar-01 AT 07:20 PM (EST)[/font][p]> Who is this Earl ?
>This set of instructions is
>way off. 5/8 is too
>big at the pump flange,
DF, the 5/8" drill is correct, since you will only go in about 1/4" at the very most so that you can have better access to drill the 1/2" hole that will go to the oil pump to quote: "First, letís start at the oil pump flange. We will start with a 5/8" dia. drill and open up the hole at the oil pump mtg. flange(he's not talking about drilling deep, just opening up the begining there). Then using a die grinder and a carbide rotary file, we will port the opening (at the) pump"
>should be 1/2. The diagonal
>to the filter pad should
>be opened up to 7/16s,
>the rest of the sizing
>is okay. Earls instuctions also
>fail to mention the mismatch
>between the oil hole and
>the bearing's hole on mains
Re-read, it says it with: "The oil hole exit at the main bearing on 1, 2 and4 will need to be chamfered to make the oil hole line up with the hole in the bearings." Right after it says to tap the 3/8"-24 at the back of the block for the lifters.
and does not
>explain the restriction problem at
I will give you that one, he does fail to mention it. but I believe the instructions originally came from some publication from the 70's and the earl might be the earl from FPP the instructions aren't his as far as I know, but it only mentions him for matching the gasket to the oil pump.