I have a 1973 F100 2wd, 360, 2 bbl, auto trans (I think C4). I would like to switch to a smaller V8 or a 6 cyl engine. Can someone recommend a good engine to use that is likely to work well in my truck and with my transmission?

I want to get away from the 360/390 for better fuel economy and to get away from the exhaust manifold problems that this engine tends to have.

Thanks in advance for your advice.

 

Your FE model C4 won't work behind the 300 six or 302 V8, or the 240 or even 250 sixes if you want to go smaller.

This is another case where you might end up saving gas, but not a lot of money.

Is this going to pull heavy loads, see the freeway a lot, or what?

--heavy loads, a pre EFI 300 with an 88-93 AOD

--freeways or just driving, 302 with same trans.


Low cost alternative is taller gears, depending on what you have. You can put some tall gears behind the 360, find a smaller 2bbl, tune it up as best you can and see some improvement.

What axle do you have now? You should have a 9 inch diff with a drop out carrier ("The poor mans quick change) which will allow gear changes in about 2 hours including cleaning the dirt from under your finger nails and washing your clothes.... There should be a tag on one of the studs holding the carrier to the housing. Look for numbers there. My guess is 3.25s.

 

Funny thing about the 360, it was always a gas hog. Especially the years 1972 and up. They changed the cam timing with a different timing chain set, which helped emissions, but did nothing for power or gas mileage.

If you want to swap the engine, you'll have to get the engine mount perches/towers from an FE-equipped truck. And of course, like 85e150six4mtod said, the tranny.

The best advice would be to make sure the entire thing is well tuned up - then, check the timing and advance it another 5 degrees or even more. Advancing the timing helps the engine run more efficiently, it might help with the MPGs a lot.

My '74 highboy had the 2bbl 360 in it originally. It was a gas hog, lucky to get anywhere near 10MPGs.

I swapped in a high-performance 390, with 11:1 compression, big lopey cam, 750 holley, headers, everything, and got 15MPGs.

You MIGHT try headers and a good exhaust first. A 4bbl carb would be a good thing too (600cfm), use a cast-iron 4bbl from a junkyard. Heavy, but it's just as good as an Edelbrock Performer.

To be honest, whatever truck you have, a 302 might get just as horrible gas mileage. An overdrive tranny (AOD) will help. But then you get into custom driveshafts, etc.

Either way you look at it, it's going to cost $X amount of money to do the swap. Could you possibly save that $X on gas if you got 50% better mileage in the next 3 years?

And then, take the gamble that you MIGHT get that 50% better mileage? A 302 in a '70's F-series is not known for gas mileage.

 

The trans you have is a C6 and only useable on another FE motor (360/390...). If you want to swap to another motor family, you will need a tranny to go with it. Lots of things to consider to save gas, including buying a beater to drive and have fun in the truck.
--Mike

 

Probably the best advice I've ever heard when it comes to mileage

Besides a raw (preferably rotten) egg under the gas pedal, that is

 

"I swapped in a high-performance 390, with 11:1 compression, big lopey cam, 750 holley, headers, everything, and got 15MPGs."

Hi. I put what I believe is a '69 390 from the yard into my '72 F100 twenty or so years ago. It had and still has a lot of chatter - lifters I guess, and I've not put more than a couple of thousand miles on it at best - a 'moving' truck basically. . Now I'm trying to bring it up to healthy so we can use it to tow our little (1400lb) tent trailer and visit the great places. I put a new carb on and replaced all the elec system. A guy is coming this w/e to see what can be done to quiet it down and try to get the gas consumption back down to where it was before we switched out the carb - around the fifteen you say you got on your 390. Runs fine but sucking gas now.
My quest is to get the fifteen again. Wish me luck.

 

holy old thread, batman

 

old bothers you?