i've been debating an engine swap for my 77 f100, and i was wondering if I just swapped a 400 in place of my 351m, would i be able to tell much difference between the two? just curious.

 

10-12 hp and about 50 lb/ft of torque difference, as OEM brand new.

http://www3.telus.net/cbradley/Engin...fications.html

If you are swapping in a high-mile used wheezer 400, I wouldn't expect much difference and if you got better results, it would be a bonus.

If you are rebuilding before the swap, and you rebuild to stock smog motor specs, you need professional help.

If you rebuild to current specs, even a mild build, you could expect 100 more hp and 100 ft/lb over your 351m.

 

i was just considering a rebuilt/remanufactured 400 engine, since it is a bolt-in deal.

 

things you need to do to get the most is good timing chain that has straight up timing not retarted. Also a 4 barrel intake with atleast a 650cfm carb. If running a edelbrock go 750cfm. I like the (quick fuel SS)650cfm or bigger annular carbs really run well in a truck application. I would go 750cfm if more compression and more cam were applied. the weiand intake dual plane works wells also. good engine and good luck with 400.

 

For noticably more power well under the 1000$ mark, yes, put 500$ into a 300$ 400, and drop it in. No transmission/accessories/mounts changes, all of which will get suprisingly expensive, you can tear down your 351 for practice, and with a roller timing set, set straight up, any aluminum 4 barrel intake, a 4 barrel carb, a set of headers, and for 100$ more a new cam and lifters, you can make a ton more power, way noticable.

Be advised though, take it EASY on an old engine with a new top end. Before buying the engine, try to hear it run, and if you hear ANY knock, don't buy it, the extra power will be an instant kill, and if it's not still in a vehicle, insist on dropping the oil pan. Look at the oil, look for metal dust/shavings/chunks, try to wiggle ALL of the rods side to side, if any move, again, it's trash. If it passes that test, before you buy any parts, take out the cam (5 minuts if you have it apart for an intake and timign set) and look at the cam bearings in the block. If you can see copper, or there are grooves or chips, really think carefully before buying your parts. And finally, be honest with yourself, and if you are someone who even might try to spin the tires, hotdog in a parking lot, or generally give the engine a hard time, don't waste your money on a 400 and a top end build.

I made that mistake last year, and I'm already having to do a total rebuild, but if you just want a little more oomf, and you'll treat it nicely, go with everything everyone's said above.

AleX

 

That's ok, but check the specs on the rebuild. The power and economy killers in the 400 are:

--retarded cam timing. A 1971 timing set, or a performance set brings it back to "straight up".

--low compression. Stock is about 8.4 iirc. You should be able to run 9.5 without trouble.

--cam. Probably the biggest power killer of all. A newer "RV" type cam will work much better.

--intake. Stockers are 2bbl. Better manifolds and 4bbl carbs are available.

My guess is any off the shelf 400 rebuild is going to have all stock specs--which is ok if that's what you want, but why not get LOTS more power for the same money with the right parts?

Read on:

351M/400 Performance Build Up

High Performance Options for the 351M/400 Engine .: Articles

TMeyer, Inc. Precision Automotive Machining

 

Engine Testing With A Holley 750 Street HP Carburetor - Classic Trucks Magazine Here is another article to read. For a cheap RV cam, I used elgin here. Elgin, Hyd. Flat Tappet Cam, Ford 351C/M, 400, .486/.512-Competition Products Good luck, and I look forward to seeing how you go about this.