Hey beedub did your sit right on the 400 mounts.? Cause if so that'll make my swap much easier as I have a complete '79 3/4 2wd 460 to pull from and another complete 460/C6 on a pallet.

 

Look into L&L 460 swap motor mounts. Now the C6 bolted right up so that is positive. The 385 series and the 351M/400 mounts are different.

 

Just my two cents and experience.
I've got a 400 6.6 and its a damn good engine. Unfortunately ford released it a bad time. Government emission regulations at the time really dampened this engines capabilities. You can really sqeeze some *** out of the 400, it just takes a bit. The easiest things are a cam ( I'd recommend comp cams) new carb ( holly or edlebrock -I have a holly), intake manifold, and exhaust. If you really want some ponnies you can put some 351c heads on it and Keith black flat top pistions.

 

Did your truck model offer the 460 as OEM? If not, it won't smog.

 

But that is for the 4x4. The 2WD F250 could be ordered in 77 with the 460. Some of the camper specials even had 4 bolt mains from what I hear.

 

No 460 was ever offered as a 4 bolt main. Only 429 super cobra jets had 4 bolt mains.

 

well after doing some digging on the 'net, ive found CARB/EO approved headers(Hedman long tubes), and the 'Brock 4 bbl intake. looks like i'll be doing the headers first (after they're ceramic coated first of course). thanks for all the info and help guys! Maybe theres hope for this anemic 351M after all !

 

I really don't think there is...simply not enough cubic inches to "get by" with basic performance bolt-ons to get an adequate power plant for a 5000lb truck that will see occasionally tow use.

I really think you should spend the money on a better engine to start with, considering your intended use.

Feel free to post before and after dyno results for us though.

 

'clever-
i tow maybe 10 times a year(my snowmobiles). i think with a header install and a better flowing intake 4 bbl manifold along with a 600 'brock carb i'll get the improvements i need. someone chimed in earlier and stated stock the 351M was grossly rated at 134 hp. What the heck was Ford thinking ??? Good grief! if i can squeeze more torque out of it i will be good to go, plus another mpg or two would be nice. my truck holds about 48 gallons of fuel when full, be nice to have it last longer than 450 miles.

 

I have heard horror stories of 460's getting 5mpg!

But these trucks were around when gasoline was what, 0.45 a gallon (guessing) My 351m supercab stays PARKED most of the time while I run my little mouse 302 66

Picked up a 400 79 dually not long ago.. My combined MPG's are plummeting so I think my next will be a diesel VW bug!

 

I just happen to know of one that'd be for sale... Even has the man pedal...

 

well after changing the cam timing to straight up (from 4* advanced) its still a pig. i went to the machine shop i deal with and we dug out a newer 400 block(with the build date code past the 3/77 bad casting) the cylinders were standard bore, and they have a 400 crank on the rack that has been cut .010"/.010" it just needs to be polished. also dug out 12 D1AE con rods for it. the cylinder head guy has a set of 351/400 heads that are ready for refreshening. gonna do some 7/16 screw in studs with roller rockers. comp cams make a decent roller cam i like (#32-421-8) for a roller conversion to roller hydraulic. havent decided on pistons yet but will probably be around 9:1 with a +.030" or +.040" oversize bore. should come out to be around a 406-408 CID
i have had enough of 8 mpg and 134 hp. looking for 275~300 and 12 mpg.

anybody build a mild 400 and what did you get for hp & torque ?

 

also thinking of an edelbrock performer rpm and 600 cfm 4 bbl. headers as well

 

Ok - I will go there...


I told you so!



Make sure the pistons you get have a taller compression height to get the piston top flush to the deck.



I had a 400 with cheap summit cam, heads decked .030 (pistons still down in the hole), cheap in the frame headers, performer intake, holley 750 DP, and I tuned it on a chassis dyno to 240rwhp/355rwtq.


Same day we tuned my buddy's 416FE with iron CJ heads, 10:1, headers, rpm intake, holley 750, and way more cam - his made 275rwhp/400 rwtq.


I was pretty pleased with that 400 for what it was.


BTW those are mustany dyno numbers and not dyno jet, which is about 10% lower. I figured that 400 was about 350-375bhp.

 

I built a 400 back in 85 for a 79 4x4 I had. My cousin had a 76 4x4 with a 390 (and it was really a 390 he built and put in.) My 408 would pull him off the line on the road and it "felt" significantly stronger than his. We never hooked them together to see which one would pull the other but I have no doubt mine would have prevailed.