I am going to rethink about the 460 thats in my 66

[66camperspecial]

Went and towed back a 95 F150 that will be my next beater truck today,it was a little more then 150 miles round trip and it used almost all the gas out of the tank so I figured I got 8 or 9 miles to the gallon. I filled it all the way up where it would take no more and its below E now so if I really want to drive it I will need a slightly smaller motor,I really like driving it now that its a 1/2 ton and really goes down the road great with the highway gears and will need to take a trip with it empty before doing anything drastic but I have a 351-c 2 bbl motor in a 78 parts truck that I need to get running and see if its good enough to just drop in. I had the 351 running but it sounded out of time so I pulled the timing chain cover off to find out the distributor was 180 out so time to put it back togather,a 351-C in a 78 looked strange but someone put it in to replace a 302 and has smallblock mounts and C-6 so if it runs good might go in next winter. The 95 is set up to tow and has working a/c so I will use the 66 as a toy and find a light car to put the 460 in and hit the track.

[ezernut9mm]

man, i got my holley dialed in on my 460 and there is no way i could do without. this truck is gonna get me in trouble.

[bruceandersson]

What about an overdrive transmission? Its been a while since I've drive anything with a 460, definitely on the large side of things. I got between 15 and 17 MPG driving my long 66 long bed 352 with 4 spd across the country.

[64 f100]

I think you might not gain much fuel mileage with the 351c especially if it is a four barrel engine. Two barrel heads would be the better heads on the engine for fuel mileage, and even then I suspect mileage would be poor under load. After running the 460 , I think you would be not so happy with the 302. I like the 351w but that is my preference. A mild cam and four barrel intake , headers and you might be happy with the 302.

Rich

[66camperspecial]

I love the power the 460 has but I am afraid I wont be able to drive it very far and I am glad gas prices are down or it would have to go much sooner,I was afraid even converting to a 1/2 ton would not help with the fuel consumption but on the bright side it effortlessly flies down the highway without the motor spinning too fast now. The 351-C I have is the 2 bbl motor and will be getting it running soon to see just how good it is.

[ThinLizzy13]

Are the 351's similar to the 352 performance wise?

[LM14]

My guess is your 35C is actually a 351M. Either way, they se basically the same head but different blocks. Neither engine is known for good mileage. Bottom end torque of both is nowhere near as good as the 460. The 351C would have a small block tranny bolt pattern while the 351M would be the same as your 460 bolt pattern.

I would look at a good tune and rear gears to fit how you use the 460. It's never going to be great but it's a truck!

To answer ThinLizzy13's question, the 351C (or M or W) have absolutely nothing in common with the 352 and have totally different manors.

SPark

[66camperspecial]

I first thought it was a M but did some looking and it has smallblock mounts and has a points distributor,looked at the back of the block and has the smallblock bolt patters so someone blew up the 302 and stuck it down in its place. I am going to order a new timing chain set since it is a little sloppy and put it back togather and see how it runs. If it runs good it might be going in next year since I have a bunch of stuff to do this year. If gas stays where its at then the 460 will not be much of a problem but since I really want to drive it a smaller motor will have to go in eventually,I am going to pull some plugs today and see if a little carb tuning is needed.

[brute66]

build that 351C would be my opinion. get an aluminum dual plane intake, electronic ignition and a good exhaust system and i would think it would provide good torque and wouldn't have to work as hard as a 302 thereby potentially getting equal fuel economy vs. the 302 (maybe better economy with a load vs. the 302). Those 2 bbl heads flowed pretty good and weren't overkill like the 4 bbl heads. In fact, the Australian Cleveland had 2 bbl sized valves and ports and small combustion chambers. They worked!

[Toyz]

You can buy a bunch of fuel for the price of some of the suggested modifications. IMO, attention to details such as excellent tune with quality parts, a more efficient ignition system, optimized fuel metering, and low rolling resistance tires are apt to yield as good of results as the proposed engine change. Correct brake adjustment often results in mileage improvements also.
Paul

[ThinLizzy13]

If you're really worried about fuel rig up one of those sixes you have laying around lol.

[unibody madness]

Better breathing, and an electronic ignition is the way to go for sure on the 460. The pre smog timing set (71 or older) will also net better power and fuel efficiency.
Headers, proper carb, timing chain,D S dizzy are the places to start

[66camperspecial]

I checked a couple plugs and its burning good and it does have electronic ignition and dual exhaust,now that I have a truck I can use for towing the 66 will eventually get a smaller motor,the 460 is going to be overkill now so if the Cleveland is not that great I am going to be on the hunt for a 351-w to drop in it. When I started building the 66 I had visions of a slide in camper and pulling a car trailer but that is not going to happen right now,its just going to be used a parts chaser so a 460 will no longer be needed for torque. For what I am going to do now a 302 might work but I have time.

[ezernut9mm]

the fuel injected 351 with overdrive and 4:11 gears in my 93 lightning barely got 15mpg. i did get 17 on a road trip from kansas city to indianapolis. bottom line, you wont get spectacular gas mileage in one of these trucks...ever.

[66camperspecial]

I know I will not get great gas mileage but I would like a little better then what I am getting,I might try to do some tuning on the 460 first but keeping other options open. I have the 351-C back togather and should have it running after work tomorrow after work and hope to take a longer trip empty in the 66 soon.

[LM14]

351C will get bad mileage and have no bottom end. They need to be wound to work right, even the 2bbl motors.

It will take years of driving to get back the money you spend on an engine swap...if you ever get it back. You should be able to get 12-15 MPG out of a well tuned and maintained 460 with the right gears on the highway. I doubt a Cleveland will do much better. Carb engines will not get the same mileage an injected engine will due to the constant corrections available with injection. A carb is just a controlled fuel leak.

Don't confuse a smaller engine with better mileage. You may gain more by working with tune, gears, overdrive and tires than you may with an engine change. Takes a lot of miles to recoup the expenses of an overdrive or engine swap, how much would you drive it per year?

I know my 351C is going to get lousy mileage but it should be a lot of fun.



Good luck with your choices.

SPark

[ezernut9mm]

i believe doc pepper has spend many hours in the pursuit of mileage and actually has accomplished some headway. you might pick his brain.

[64 f100]

Okay, we have one person with 411 gears complaining he only got 15mpg, and I would be very happy with consistent 15 mpg with my 390. Actually a consistent 12 mpg would be an improvement. I was running overdrive with 3.50 gears, but have a very heavy hoof. I expect 15 to 17 to be a good average, if achieved. As to fuel injection to carb mileage, might be some improvement but frankly is it worth the cost and effort . Gas is relatively cheap at the moment and my expectations for the future prices are grim. Maybe the question we need to ask you is, what are you wanting in the way of fuel mileage? Something else that needs discussing at this point is what condition are your engines in? Used engines with unknown mileage, rebuilt, etc. . Just swapping an engine in, in used condition, without being able to drive it before installation leaves you in a questionable situation. A lot more than just the engine affects fuel mileage. What grade tire are you running? If running light truck tires with soft side walls and a lot of weight causes rolling resistance. What tire pressure are you running? I always run the max amount allowed or just below it, so that increased tire pressure from heat expansion will still keep it close to max allowed pressure when running. When going for fuel mileage start where it's cheapest. Do the little things before spending big money. Air pressure , weight of oil your using, condition of all components under the hood, Inspect and check. Once you've done all the little things, do a reality check. Just how many miles a year are you going to put on this truck? How much fuel does this represent and can you change your driving habits to affect the mileage?

Rich

[banjopicker66]

I have been looking at changing out my 460/C6 with a 302/C4 for the very same reasons you mention - better mileage, especially around town.
I think I have concluded that the cost will not be worth it, even if I could find a good running, dependable 302/C4 combination from a donor vehicle for less than $1500.
I have tweaked my 460 to what I think is the limit. My '66 has an '80s 460 with carburetor heads, Edelbrock Performer intake (not the RPM intake), a 600 CFM carburetor, straight up timing chain, DS II electronic ignition, rebuilt C6, dual exhaust with Flowmasters and a 3.25 rear axle.
The only upgrade I did not do was headers. The research I found indicated that the stock exhaust manifolds flow almost as well as headers, and so decided to stick with stock manifolds.
When I took it to Slick Stock 2006, I measured the gas mileage pretty closely. I even had my wife follow in the van to make sure the mileage registered by the truck's odometer was accurate (it was, by the way).
I registered slightly more than 15 MPG at 65 MPH, but that was empty, not hauling any weight or trailer.
Over the next couple of years, it averaged out to about 15, whether I was towing a heavy car on my trailer, or running empty.
In stop and go traffic, I got about 8-10 MPG. Empty or loaded.

I think that after all is said and done, a 302/C4 swap is a long shot before I recover my costs.

My truck is disassembled right now, and is still back home in SC. I hope to sell my house and move back home soon, partly to reassemble my truck before my condition prevents me from doing so.

Hope this helps.

[banjopicker66]

I think the keys are these:
Straight-up (pre-'72) timing chain
600 or 625 CFM carburetor
Good flow for intake and exhaust
DS II electronic ignition
Rear end ratio suitable to good freeway mileage, that the 460's power can overcome when hauling or towing
Good tune-up