390 vs. 400
 

I've been looking at trucks for a few months now and have some questions about engines. I've owned a four 70's fords, these had either the 302, 351M or 400 engine.

I'm going to be buying a crew cab with a auto to pull a small 3500# camper and need something reliable for long trips. Some of the trucks I'm looking at have either a 390 or 400 engine.

I know nothing about the FE enignes. Could someone tell me a little more of the pros & cons between the 390 & 400 engine?

MPG will be about the same, maybe a little bit better with the 400 but nothing to pay attention to. All 390's came factory with more power than the 400 ever did. I've seen/heard a beefed up 400 before they are nice engines. I'd go with a 390 though, that's what I have and it's a very good engine. A lot of people (including non Ford guys) will say it's the best, or one of the best engines Ford made.

I also wondered about using today's gas. I'll be traveling in whatever I buy so I don't want a picky engine when it comes to gas.

I have owned 351m, 400, and 460. My brother had 2 390s One he built into a 10:1 and low/midrange cam, stock heads and valve train. The other was stock in a 75 highboy But I think I remember it coming out of a car and being transplanted into that truck. That one had a 4 spd the 10:1 had a C6. Both ran 36" super swampers and 4.10 gears. I think the 2 390s were leaps and bounds over the 400. The 400 has been a very dependable engine to me, other than the vapor lock in the summer due to the metal fuel line next to the exhaust, easily remedied with some insulation or an electric fuel pump. I thought the 390s had more power, ran cooler, came with 2bbl or 4bbl carb factory, had awesome low end torque, the name of the game in a 3500+ lb truck. I like the 460 the best, but It isn't a 390 or 400. I like the 390 far better. They are nice sounding, good power, 10-12 mpg avg. and very simple to work on. I wouldn't stray from the 400 if it runs good, but If you can go to the 390 in a good sound truck, I would do the 390. Just remember one thing: 360s turn into 390s on sale day. Avoid the 360. They were low compression, short stroke, gas hogs, and very low powered. A 390 crank makes a 360 into a 390 but I doubt you want to do that.

I'm sure it's been asked but what's a simple way for me to identify the 390 vs. the 360?

About the only way to tell the difference, is checking the stroke.
Remove the plugs from #1 and #4. Roll the crank around to TDC. Using a wooden dowel, insert into #1 and mark where it meets the head after contacting the top of the piston. Remove, and insert into #4, marking again. Measure the distance between the marks. ~3.5" = 360, ~3.75" = 390.
The 390 was offered with a 4bbl carb, the 360 wasn't, but the intake will swap, so this cannot be used as a sure-fire method. Otherwise, these 2 engines are identical on the outside.

Does anyone know the factory hp on a 390:-huh.......sry:-hijacked

They range from "201-401hp"

You can run the vin. It isn't for certain at this point either, but if the thing has a 4bbl, a 390 engine code it probably has a 390. if it is a 360 engine code, look out. But if I am remembering right here, the 390 came with a 2 bbl or a 4bbland 360 2bbl only. No external identification.

While I've always been fond of FE engines, I'd still think the 400 is the better way to go. The parts are cheaper, and you can make a reliable 400 with good power for relatively low dollars. A good cam, a straight up timing kit, a 4bbl carb (e.g.: Holley 650) and some work on the exhaust (i.e.: headers, new muffler, duals, etc.) should wake things up a bit.

Don't get me wrong.....the 390 is a good engine, but they're getting a little more scarce now, and the 400 is plentiful and cheap for the potential you can get out of it.

390 beats the 400 in stock condition. I prefer the 400 if you are doing an engine build.

I don't think it matters a whole lot. I don't like the 400 due to the heating issues they have. I think with the "standard" radiator for a 400 and a clutch fan and the recommended 195* thermostat and the airconditioner running, They actually won't stay cool on a hot day in stop and go traffic. Upgrade the thermostat to a 180 and go big on the radiator and make sure you havea good fan and water pump you are all right, but I have never had a heating issue with a 390 or a 460. The heating issues are fixable with a good radiator, good fan, and make sure your water pump ports are lined up, you might have to polish them to get rid of any flow restrictions. I like the 390 for that reason alone. The 400 is good and stout but mis understood. I have never seen one that had the correct thermostat in it until I fixed them. I have put a lot of miles on a 400, off roading, highway miles, towing, and in town. In the summer with the AC running and the engine idling with an automatic, The temp guage will creep up. If you shut it off and run into the bank then back to idling around town the temp gauge pegs in less than an hour of idling on a 100* day. I flushed radiators, put electric fans, replaced water pumps, new fan clutches, new thermostats, replacedradiators, put oil coolers, and I could never eliminate the problem. It was almost fixed but now and then, she would peg that guage. For this reason the 400 is lower than the 390.

I had this happen with 3 different 400s and they were all similar symptoms. I think the 400 needs a big radiator and a good fan. that seems to fix them.

Either one I get will remain stock unless I add a 4bbl. One truck is a '74 and has a rebuilt 390 4bbl, the VIN calls for this as well. The other truck is a '77 with a stock low mile 400 2bbl and loads of smog equipment.

I don't want cooling issues, I will be towing a camper and doing a lot of around town driving on hot days with the A/C on.

Well, I probably would opt to the 390. Ifthe 400 has a good big radiator it might befine, but watch it. Mine had heating issues. I would say either is fine but probably do away with the smog equipment on the 400. That helps too. I read that the 400had a waterpump passage issue that you had to gring the passages to fit the pump and that helped a lot. I don't have the solution for the 400, i bet that is why ford only made it in a truck for like 5 years.

I recently pulled the 390/ 4spd from my truck and replaced it with a low mile 400m/c6. I only did it because my 390 is in need for major rebuild and i got a good deal on this engine. When i had my 390 it was quite torquey, it was stock heads, 2bbl long tubes headers. When I drove the 400 in the bronco it wasnt as torquey but it needs a tune up carb clean and fresh gas. From what I see so far, I prefer the 390 but I found parts availability difficult or people look at you like your from outter space and ask if you have a punched out 351W.