So.... my new (1977) crew cab F250 4x4 has a 400 in it... runs decently well -- we're still working out a few issues with the carb, but I think we can make it run nice. Stock 2 barrel carb, stock cam, etc. 4 speed NP435. It does have a lot of leaks and needs sealing (intake gasket, oil pan, quite possibly more).

I also have a 300 six (from a 1968 truck, so pre emissions), with a new cam (higher torque and efficiency model, Compcams 252 I think), Offenhauser DP intake, headers, 4 barrel carb, and maybe some other stuff that I can't remember right now. It'll have a 4 speed NP435 with a Ranger overdrive, so 8 speeds.

I'm trying to decide whether to tear apart the 400 and seal everything, or just swap in the 300. It will be a fairly heavy truck when it's loaded up with tools and stuff, but probably not used for towing very often. I am driving between 5,000 feet and 10,000 feet elevation though... I'd like the better fuel economy of the 300 for sure, but is it going to be a complete dog going up hills, even with the 8 speed? Or, will the mods I'm making to it get it into similar power range of a detuned stock 400? Compcams software says I should be getting 200HP, 300tq out of the 300 -- which is very close to what the '77 400 was rated, I think.

Opinions?

Thanks

Zeke

 

That's probably more than a stock 400. The 300 is a much more reliable engine than the 400 with a few upgrades the 400 could be made into a torque monster. Cam, advance timing, intake, four bbl, and headers make a pretty decent engine out of the 400 and it will out perform a 300, but will get only 75% the mpg... Maybe. 300s can get around 16 on the hwy, 400 would get around 12 on a good day. If you do a lot of heavy towing I would try and build up a 400. everyday driving a 300 is much better because of mileage. In the end its up to you. I personally live the sound of a v8 and my 79 isn't a daily driver so mpg isn't a big deal to me.

 

This is going to be more of a daily driver.

I know what you mean about the v8. I was driving my '56 chevy 2 ton stakebed today and it sounded good... It gets around 4 or 5 mpg with a big block 348 though. So only when work actually calls for a two ton truck

 

From everything that I have read, the 300 needs to have the head ported and larger valves installed. Can anyone back me up?

 

I had an '83 f150 3.55 gears with a 300 with 4 barrel and headers and that thing had *****. Seemed like more power than any 302 I've driven since. Of course the 80s model trucks are lighter. As for towing I wouldnt sweat towing anything with the 300. I cant speak on porting the head or larger valves though. The biggest drawback, as mentioned above, is the lack of the V8 sound

 

Both are a good motor. At the end of the day it's gonna come down to personal preference. I would do which ever is cheaper. If you go 300 look at turboing it.

 

The 300 head starts to run out of breath around 3500 and will only need work if you habitually run past 4000 or cruise in the mid 3000 RPMs. The mods listed are spot-on for a stock headed 300. The low-end grunt of the 300 is great on a wide-ratio granny-low fourspeed.

Bellhousings might not match between 300 & 400M either.

If you already have to pull the 400 to freshen it, pop in the 300 and see if you like it.

 

Of course if you turbo it like mentioned above, the head is fine.

 

I fixed it for you

400 uses a "big block" housing. 335 and 385 series engines share the same bolt pattern. (351C, 351M, 400, 429, and 460)

 

Frame stands, bell housing, clutch fork, and all the stuff that bolts to the front of the engine is different.

Having said all that, my opinion is 300 biased. I hate 400's with a white hot passion. I've owned four of them and they all had severe bottom end issues. I have ZERO desire to own another 400. The stroke they have builds excellent torque, it also makes the engine prone to blow the bottom end all over the pavement at random intervals.

You have a 400 that's run great for years? .....great for you. I won't own one. (Yes, I hate them THAT much)

I wiped the bearings out my 300 six about 9 or 10 months ago with a bad fuel pump (Leaked gas into the crank case) and it's been working away with 2 quarts of Lucas and 5 quarts of 20W50 in it ever since. This includes pulling a car trailer most times I fire the truck up and hauling cars long distance.

The 300 will DEFINITELY be more durable than the 400. Under load, the 300 through a single glass pack sounds like a 9N tractor pulling a load. (A sound that I love, by the way)

 

if your truck is heavy i would go 400. if truck heavy and you have a 300 you will not get 16mpg. had a fuel injected 300 and loved that truck and once i put weight on it fuel mileage dropped off and just got along. very reliable truck in my college yrs, no regrets. but if you have a 400 you have the ability to have a 12.250 clutch for high torque/towing application. also you can upgrade 400 to serious power/torque. just recently built a 400 just for this reason. One of the issues with 400 is oiling issues and easily upgraded and cheap. cam bearing upgrades and tim meyer sells these cam bearings. keeps oil to the crank. stock crank clearance needs to be around .001 to .0015 and your oil control/pressure will be excellent. fuel mileage easier to get a overdrive tranny with small block setup. The ZF trannys are a easy bolt in with small block but with the 400 its some serious work and though out process but very doable. Just done this on a 400 with the ZF trannys. now a new tranny in 4wd app is now available. T56 magnum 6speed or tranzilla for a low low fee$$$$, ouch! will have one next year. things to consider and just rambling!

 

I have a 1954 Ford 600 tractor -- just a little newer than the 9N. I wonder if it sounds the same.

I already have the right bell housing for the 300, and have a spare 435 and all for it -- all I'd have to do is get a custom driveshaft going to the divorced t-case (since the ranger splitter makes the tranny about 8" longer than stock), and of course motor mounts (I have the correct mounts that came on the 300 in the '68, but is that the same frame as the '77?), and figure out how to get the power steering mounted on the 300 and such.

 

You can buy motor mounts for the 300 as it came in every 4x4 model but f350 I wunna say til its end. If you have a granny gear you won't need a big engine, just low end torque. 300 all the way all day. Unless you wunna build that 400 you would be putting in a stock 'dog' motor when you could be putting in a semi built motor, and get worse mpg still lol

 

I agree. Going back to the title: stock 400 vs. modded 300 the modded 300 would be a better engine. If you were willing to rebuild and mod the 400 I would personally vote 400. There is a lot of untapped power in a 400 that isn't too hard or expensive to get. They are not bad engines if you spend a little time with them and address a few of their issues. Some people hate them, I have a 400 in my 79 that my uncle bought new, and it has been a hell of a good motor. It's just now getting to the point of needing a rebuild. I agree they were dogs because of all the emissions crap, but change a few things over and they will stomp a 300. In the end it's up to you. Think about how your going to use the truck, and what you expect out of the truck. Make your decision based on those answers.

 

I like both... I'd add its worth verifying the 300 has hardened valve seats. A '68 head may not have had them. Needed for lead free fuel or you may sink the valves with hard running.