performance/mpg for my '69 with a 240
 

I have a '69 f100 with 107k original miles on it......recently with everything still being original i've had to replace the distributor, starter, solenoid, master cylinder, alternator, etc.. I have also added a K&N air filter and a single Flowmaster muffler with a y-pipe for duals running out the back....These things have upped my mpg and also made the truck run better than ever(not that it didnt run good to start with).....i've been doing some research and i've found the offenhauser intake manifold that converts to a 4bbl carb. instead of a 1bbl., also a comp cam., and a pacesetter header for my engine.....just wanted everyones thoughts on how much of a difference these things would make as far as gas mileage and performance?? and also if it would be worthwhile to invest in these things? Thanks

To each his own, but for the money and time your going to spend on that, you'll be doing better performance wise, and probably gas mileage wise to go with a 302.

I bought a new 74 F100 with a 240 back in the day. Drove it for 120K miles, got 16 mpg no mater what I did to it. Also the truck was under powered. Want performance, get a V8.

Hey Bigcash, welcome to FTE, I've heard of guys getting more power out of carbed 6's by doing exactly what you're doing. And even using 300-6 EFI exhaust manifolds. Any headers do great wonders over stock exhaust manifolds. And intakes alike.

I had a 300-6, running around 9.5:1 compression with a 72 240 head, some sort of high lift cam, Offey C series intake, 354cfm Motorcraft 2150 2BBL, efi dual manifolds, and dual 2" pipes off the factory efi downpipe, ran great. I drove that truck from Connecticut to here loaded, crossed the scales at about 11,500lbs with full tanks, between the truck and trailer.
I was pretty happy with the engine, it pulled well, got ok mileage for how hard I beat it, but needed high octane gas due to a mistake I made on the port job.

my only problem with just finding and dropping a V8 in is that this truck is my daily driver and an engine swap may put me out of commission for at least a few weeks if not more....also with it being numbers matching the original engine with only 107k miles its hard to part with that, so im looking at more possible things to do to it to make it run stronger and whatnot....the engine is already surprisingly stout for a 6, especially in that big a truck and i've had absolutely no problems out of it whatsoever(other than expected maintenance and parts just getting old)...i dunno i guess its sentimental to me as the truck is.....i bought it last year when i started my new job while taking some time off from college as something to drive daily and tinker with and now i cant seem to part with it even after numerous offers for more than i originally paid and at 21 i hope to be able to in the end complete my restoration and pass it down to my future children

The 240, 300 six and 302 V-8 (and I think the 351W??) all share the same bellhousing, so a swap to any of these would be relatively easy as long as the donor engines have all the accessories and brackets; you won't be looking at serious changes.

If you want high RPM performance, swap to a 302. I recommend you stay away from a 302 for a truck, though, unless you are going to use it for cruising, and aren't going to use it for hauling. The short stroke of the 302 makes it more suitable for higher RPM applications.
If you want truck power, stay away from a 302, and go with a 300 six or a 351W. Their longer strokes make them much more suitable for power and mileage in a truck.
If I were in your shoes, I would look at a 300 six swap, and put some minor performance upgrades like a 4 bbl intake on it. The 300 six was used for over 30 years in trucks, and has proven its worth.

Good luck!

im leaning towards keeping the 240 and just seeing what i can do with it......so im curious.....anyone ever heard of putting the 300 factory dual exhaust manifolds on and running true duals out of a 240 and what that does for it???

and also would the offy intake with a 390cfm carb. be too much for the 240?

Unfortunately, there is no replacement for displacement. That little 240 is a great and dependable engine, but you can only get so much out of it.

Probably the best balance would be a 300. You get a significant increase in cubic inches, a great increase in power and upgrades, without having to make a lot of modifications.

Of course, I think your idea of keeping it original is great, too.

Just my opinions!

Keeping the 240 is a good thing if you can accept it's limitations. I loved mine, but I didn't use the truck for much heavy work, it was my daily driver. You will have a few problems trying to tow or haul heavy loads with the 240 though, it just doesn't have the grunt.

I have a 1970 F100 with an 89 fuel injected 4.9 conversion. The engine is totally stock with the stock ECU the only mods are removing the EGR and air pump and TIG welding a custom down pipe off the EFI manifolds to a single 2.5" pipe and a turbo muffler. It has a T-18 four speed and 3.50 gears and gets 22-25 MPG on the freeway and will get no worse than 17 MPG rodding the living heck out of it. I estimate the engine makes 200+ horsepower and 350 ft/lbs below 3500 rpm and really scoots the truck around. The engine also has around 220,000 miles on it and still going very strong. It will tow light trailers under 5000 pounds pretty easily and just the other day I hauled 1600 pounds of concrete in the bed and didn't really notice it.

My best friend has an identicle 1970 F-100 2wd, but his has a 240. Everything else is exactly the same except for a '69 grill. We used a 240 crank rods and pistons in an EFI 4.9 engine hoping the much better EFI head and fuel injection would make for a super gas mileage machine with tolerable power. Nope. The 240 sucks. Even with an aftermarket EFI controller it makes OK power, but is just too small of an engine for a half ton truck. The engine will not lug along like the 300/4.9 will and gets erratic mileage probably averaging 17 mpg.

Honetly, not many people out there are concerned whether an old truck has the original numbers matching engine. I agree with those advising against the 302. I'll take a 4.9 over a 5.0 anyday for a truck. There really isn't any way to tell the difference externally from a 4.9 to a 240 except for no fuel pump. If you drop in a 4.9 six with the stock rebuilt 1 barrel carb and run the EFI manifolds you will be very happy. An aftermarket intake with a motorcraft 2 barrel would be even better. You can buy a downpipe from walker exhaust to literally bolt the EFI manifolds into your truck.

Ditch the 240. They worked in the 2000 lb econolines, but not a 4000 pound half ton truck.

Too bad you are so far away, I would swap you about any engine for your 240. I grew up with these trucks, and the 240 is a great engine for a driver. If you will check the factory ratings you will find very little difference between the 240 and 300 in power, and the 240 was 1 to 2 miles a gallon better than the 300.

Of course, the difference in the engines was the pollution controls - the 300 had a lower compression ratio and was built for unleaded gas.

As others have stated, the V8s have more power, but do you really need it? Like they say around here - "speed cost money, how fast do you want to go?"

Unless you are using your truck for heavy work - loads or towing - I would stick with the stock set up. If you want, adding aftermarket speed equipment will not hurt, but I would not expect a huge power gain.

oh, my friend,not to rain on ya'll v8'ers party,but there is a replacement, back in the 50's,60's,and 70's when we were all using gas guzlers,over in europe they used smaller engines for the mpg but used turbo's for the power facter,turbo's make alot of power very fast and cheaper and will increase mpg and power,and as we all know,exhaust is veiwed as waisted power down the pipe,but since a turbo uses that exhaust to spin a turbine to compress the air entering the engine,u waiste nearly only 1/4 of the power with out a turbo,i have plans of putting in a built 300 in my trcuk,with a turbo and all the goodies. i have seen many trcks with I6's that have waisted big v8's and still gone farther on a tank then them also....jmo and some facts

Apples and oranges, Put an equal setup on the V8 and it will still get squshed like the bug that it is. IMHO :-X10

John :-X06

You are right about the turbos, they are indeed great; I had one in my 4 cylinder 2.2 '86 Chrysler Laser, and it would fly down the autobahns in Germany at well over 150 mph.
But, I had to get out of the way of the big Beemers and Mercedes which had V8s. Or the occasional Ferrari or Jaguar with 12 or 16 cylinder engines.
It was eerie to be passing everyone like they were standing still, only to be passed at the same time like I was standing still! They have their place, that is for sure.

Turbos in trucks have limited application. They work best at higher RPMs - opposite of what trucks work at. When grunt stump pulling power up a hill is needed, a turbo won't cut it.

The difference here is not just raw horsepower, but torque - which is why the physics of the 302 short stroke motor (and most of the European motors) won't match up to the low end power of the longer stroked 300. So, even though the two engines have very close displacement, they have very dissimilar performance characteristics.

You have made an excellent point about turbos, that's for sure, and they do a good job of reclaiming some of that otherwise wasted power out the tailpipe.