Paul makes a good point. An effecient street/towing/milage porting job on the exhaust choked 460 head would not be the same as a "race port" job. The street/towing/milage port job would likely focus more on the exhaust side than the already decent looking (comparatively speaking) intake side.

A better flowing exhaust port, like a better flowing exhaust system could help milage & also help produce better low end power for less throttle opening needed to do the same amount of work.

And while removing sharp edges/hotspots in the combustion chamber on a street/milage porting job might not "increase" milage any, it could reduce the chance of power robbing detonation.

 

Paul kane,

As an engine builder and having a flow bench in my garage I have spent hours arguing this point most of it falling to def ears. Shaping ports for more flow does more for power and economy than any other mod. A stockish cam, port shaping, a matching intake and good headers is almost like a 100 to 150 HP NOS shot. I am preparing to do some port work on my D3 heads. I usaly only increase volumes around 2 to 3 CCs to get good results. Way less than 290+ stuff going aftermarket. It isnt very often I dont gain power throughout the RPM range unless there is a purpose behind it. Good luck will provide any help I can.

 

A 10 Percent increase in mileage on a 460 would be 10% of 8mpg. That would be less than 9mpg if you got that wished for 10%, which isn't likely. I live in the real world where if they claim 10% you will be lucky to see 5%.

 

All ready doing 12 in my dually keep very acurate records of jetting, spark plug readings, wind direction, driving conditions, loading, etc. Probabley get a bit more before I get headers, better ignition box, ported heads, intake and such.

Thats with a tall cap, 4.11 gears, and mirrors that probably eat up a couple miles a gallon. Still has enough power to idlle around in 5th and pull away with a moderate load.

I think it got 5 or 6 when I got it with only 72K on it at 87K now.

 

Bear, said it and I'll say it again, you can't gain enough on a 460 to make enough difference. Ya you can send $100s of dollars to gain a couple of miles per gal. !0% of 10 in case you haven't figured it is 1 MILE big gain for $600 worth of head work. I'm sure you can't gain 50% gas mileage on a 460 carbed in a truck. that is 5 MPG average.
BIGBLOCKTRENT: I've been on this board for sometime now and if you don't want to hear what people have to say then don't post. I have just as much right to my opinions as anyone else. If you don't like them then you have the problem.

 

once I get 10 MPG (unloaded) I'll be happy

 

You and me both brother!

 

Once upon a time many years ago I was designing something a customer wanted on his mobile earth drill. I t had never been done before. We had a ricent 3rd in class from Perdue engineer. He told me it was impossible he had never learned it in a book and we didnt use computers. I looked at him and said " watch me do it nobody tought me I couldnt" So I did it customer was happy the company I worked for sold bunches of them.

My first increase in milage in my 460 from 6 to 8 MPG I used a 3" hole saw purchase 3 years before and a drill I bought in 1975. It almost busted my wallet.

Hummm 30% increase cost 0 $

 

thank you everyone for your advice. and thank you bear and kermmy because if it wasn't for you, so many people probably wouldn't have posted.

 

Do you still have stock exhaust?

 

Yes I still have the stock exhaust.I will have to say with a few mods I will be able to get 10 MPG with my truck the way it is (ie headers dual exhaust and a couple of other small modifications.)
Now to get 16 MPG with a lot of talking and research the only way I will get to the 16 MPG is going to be a lot of work that in itself is no big deal but the results to get there is. I will lose all my towing,hauling ability and losing alot of weight.
1. We plan on losing the HD F250 suspension front and rear. We plan to put a IFS suspension from a 97 F150 not going to be easy.
2. The rear which looks like a sterling rear (I have pictures in my gallery)
will be dropped and a Ford 9 in with 2.73 gears are going in.
3. also we are planning on a 4EOD trans going in.

So my truck will be a F150 with a F250 frame and even then 16 will be hard to get since I have a SuperCab.

Even with all this it makes me wonder if it is worth it but I'm not going to be using it as a work truck but a true daily driver.

 

You have the dual 2 1/2" inlet muffler with the 3" outlet. Look up your outet and see if there is a perferated disc in there if so get a 3" hole saw and cut it out. There will be another perferated disc behind it cut it out too. Notice how the pipes go in and out of the muffler its the same muffler used on a 302 or 351 it has 7 to 8 " of back pressure. I used a megaflo Dynomax RV muffler. Used the aluminized one. Cost around 180$. Didnt concider this a extra expence the old muffler was soon to go rusting around the seams. The Megaflo only has 1" of back pressure. It looks like a small water heater. 2 2 1/2 pipes into a 3" dosent step on air flow keeps the piping simpler pllusss all the rest of my exhaust was good so I didnt have to pay for new stuff. It s like having a crossover or x pipe too. Later I will plumb headers to it with mandrel bent tubing an 45* elbows much better than the kinked up stuff from a muffler shop. Kould E mail you pic's if you like.

 

Sure email the pic's.Thanks I have cut out the disc out the end of my exhaust pipe but didn't do such a good job,I'll have to get a hacksaw blade to get what I missed. But I will have to get a new exhaust system on my truck I have a exhaust leak where the exhaust pipe bolts into the manifold.So I am going to get headers and a new true dual exhaust with a X pipe and flowmasters and exit in front of the rear tires.I also plan on getting rid of the front tank and get the 38 gallon rear tank from LMC and replace the rear tank so I can keep the same amount of fuel.

 

Oh I forgot to mention I tried to get the exhaust flange gasket for my manifolds and found I have the set that doesn't require the gasket.They did a change over sometime in 86.

 

I see you guys have the older carbed trucks. I am looking at a 97 EFi F250 HD SuperCab with the 460 and 5speed manual. I need something that pulls. It isn't a daily driver. I have a 90 f150 right now that gets 8-10 mpg under load (5,000lb towed) and can't get out of it's own way. How are the newer (if you consider 9 years old newer) EFI 460 Trucks like this on the mpg tuned up? I'm guessing 12-14 highway unloaded with a light foot and a tail wind. Am I off base?