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Discussion Starter · #1 ·
OK I have to tear into the 400 in my 79 f-150 this weekend to change a leaking main seal. I'm trying to find the torque specs for the main bearings if anyone has them?

Also does anyone have experiance with rebuilding these motors? the only thing that seems to be holding them back is the super low compression. I know there was a OOOOLLLLDDDDD hot rod article that rebuilt a 400 for under $2000 and made over 450lb/ft torque (also everyone loves chevy 383's, this is the same bore just longer stroke AND rods with bigger valve heads)
 

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100ft/lbs on the main bearing caps (95-105 range).

The main thing holding the motor back is low compression, heads, intake, and to a lesser degree exhaust manifolds. Athough, just a decent intake/carb and headers can really wake it up without getting into alot of work.
 

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I broke out my Chiltons, if this 400 is an orginal 78-79 400 then stock torque spec for the main bearing bolts are 95-105 ft. lbs of torque. Your stock compression for the 78-79 400 is 8.0:1. Even with low compression the 400 was still putting out more Torque/HP than any 351M/400 in any other years. I believe that the stock engine HP and torque for the 79 engines are about 250hp and 340 ft./lbs. I am also pretty sure that the stock 400 puts out more torque than a stock 460. But anyways enough on the history lesson, id leave the pistons alone, i left my pistons, i went heavy on the torque in my engine. I threw in a cam, timing set (very important), carb, intake, headers, true dual exhaust bla bla bla and ended up with a bronco that could rip 33x12.5s loose, (pls don't laugh at the tire size, this is not a my dedicated offroader, the thing is mint and i don't want to beat on it like my Jeep) with a c-6 auto (which eats up an ungodly amount of hp) and 3.50 gears, gets 8 miles to the gallon provided i don't open the secondaries, and can beat any ricer on the road without 15k under his hood despite the fact its probably only putting out between 300-400 hp. So id leave the compression alone, if you absolutly had to have different pistons id say 9.0:1 max. Also if you are looking for a site with lots of info and people who run and build 400s try http://www.broncotech.com/cgi-bin/ultimatebb.cgi search the 351C/351M/400 forum. Good Luck

MeanJ
 

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Discussion Starter · #4 ·
you guys are the shit! Thanks alot hopefully I get this thing going for now and can rebuild it next spring.

My plans for the rebuild are the

-general short block machining and bearings
-3 angle valve job and any thing else the shop feels the heads need
-a cam in the 260 advertised duration range
-edelbrock intake and 600cfm vac. holley for now (its got all the bells and whistles and is free, won't see much rocks for awhile anyway)
-hopefully up the compression a bit but not if its gonna be a pain in the ass.
 

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You need a bigger carb. I have a 750 Holley that has a fresh rebuild..... all it needs is a powervalve. There is no choke, but if you want it you can have it for $20+shipping. Im getting drunk, so this price is for tonight only. :D
 

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Discussion Starter · #6 ·
45acp said:
You need a bigger carb. I have a 750 Holley that has a fresh rebuild..... all it needs is a powervalve. There is no choke, but if you want it you can have it for $20+shipping. Im getting drunk, so this price is for tonight only. :D
haha thanks for the offer but I figure the holley is better then my leaking stock 2bbl, and its allready setup with all the shit you can do. My brother spent all the money on it then realized he coulda bought a demon from the get go and had all the same shit plus he's going bigger.

Once I rebuild the motor I'm going truck avenger or Q-jet.
 

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Believe it or not even on a serious 400 engine build a 750 pumps way too much fuel for a 400, the 600-650 range is considered optimal, i run the 670 truck avenger, runs perfect for me, i had a buddy who did the same rebuild i did on a 78 bronco, same set-up but with a mechanical 750 holley and it ran fine, but mine had way more snap, he was just killing his with too much fuel, that much gas doesn't run well with a torque based engine, it didn't have the high rpms that made use of the extra fuel being sucked in.

Mean J
 

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When I rebuilt my 400, here is what I did. I took the old motor out, put it in the backyard. Meanwhile, the sprinklers filled up vairous oriphices.. While all of this was going on, I bought a 460(use the truck motor, with a rear sump pan, with passenger car accesories), and the motor mounts/headers to make it all work. I also bought a Weiand Stealth manifold, a better cam, and had some minor opening up of the valve pockets. Needless to say, when it was all together, i had a motor that was twice the motor of the old one.. I got 10 MPG, and smokin the baloneys (36's) was no problem.
 

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If you want an easy way to bump compression, use a set of Aussie cleavland heads. The have the same chamber as the 4v heads, but use standard 2v intakes, headers and valves. I happen to have a set, with new valves and rockers, sitting around. They need decked and seats done, but you should do that anyways when rebuilding. Look in the for sale ads for more parts I have for the 400....might I add, I am highly motivated.
 

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I believe that the stock engine HP and torque for the 79 engines are about 250hp and 340 ft./lbs. I am also pretty sure that the stock 400 puts out more torque than a stock 460.
I'm sorry, but, both of those statements are untrue.
The 1980 ratings for the 400 are 153 [email protected] RPM, 296 lb/FT @1600, I can't see 79 being any different.
The ratings for my 86 460 out of the box were 245 [email protected] RPM, 385 ft/[email protected](and it has a nice flat torque curve) and, it's also 8:1 compression...
 

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ford005 said:
If you want an easy way to bump compression, use a set of Aussie cleavland heads. The have the same chamber as the 4v heads, but use standard 2v intakes, headers and valves. I happen to have a set, with new valves and rockers, sitting around. They need decked and seats done, but you should do that anyways when rebuilding. Look in the for sale ads for more parts I have for the 400....might I add, I am highly motivated.

Correct me if im wrong, but the aussie heads have the larger 4v valves, with the smaller 2V ports. If you have new valves, why didnt you have the seats done while you were installin em??

I'D still build a 460 any day over a 400
 

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Aussie 302Cleveland heads have closed chambers and 2V valves and ports
if you can get them cheap they are a great head but with 400 inches you have enough cid to run the 351C 4v closed chamber heads that are available locally
stroked 351C engines run like raped apes

Ford magasine has to choke a 351C with cast iron dual plane intake to try and make aftermarket heads look good

Iron 4V heads/cast iron dual plane:
-438 hp @ 6000rpm and 450lb-ft at 4000rpm
-also 439 lb-ft at just 3000rpm
-torque was above 430 lb-ft from 3000 to 5000 rpm
try and match those numbers with stock intake and heads from any other small block
no low rpm torque?

400 shares piston compression hieght with the 351c but the pinbores are different
bush the 400 rod pin bore to the 351c size and you can run off the shelf 351c pistons and get any compression ratio and forged pistons

750 cfm is not too big for a 400 inch engine

you guys that are junking them, I need a couple of 400 cranks and it sounds like they are more plentiful south of the 49th
 

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Discussion Starter · #14 ·
I will admit a 460 can probably going to make more power but I know the 400 is good for well over 400lb/ft with minimal mods, and guess what I already have the engine!

45acp: your off topic sale would of worked if I didnt allready have a free carb lined up
 

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The stock HP and Torque numbers between engine years are different especially between 79 and 80, the numbers were measured in engine, brake and rear wheel horsepower which made it difficult to tell otherwise, the numbers were fudged because of insurance companies and primative smog components iced the cake so its hard to tell what the true numbers actually are. Bottom line the 400 is a high torque motor that is on par with a 460, hp is another story... The cleveland pistons in the 400 are just mean, i had the pleasure of seeing a guy in who had one in a old 70s f-150, it produced the kind of HP that gives you goosebumps. And finally the 750 is too much carb for most 400s unless your are putting it on a high horsepower application (500+)if not, it bogs it down or if its too radical they like throw rods left and right due to the poor oiling system. The 750 cfm has been tested, tried, and has been found lacking, i reseached the shit outa this topic when i built my 400 and was looking for a carb. :) If you want to pick up a nice new holley or edelbrock 750 just go to any for sale forum for 73-79 F-150s and 78-79 Broncos, they are constantly being sold or traded for smaller 650 carbs that run crisper at lower rpms. Good Luck

Mean J

Mean J
 

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masterbeavis said:
Correct me if im wrong, but the aussie heads have the larger 4v valves, with the smaller 2V ports. If you have new valves, why didnt you have the seats done while you were installin em??

I'D still build a 460 any day over a 400
The heads I have are sitting on a shelf right now. I was in the process of collecting parts to build up a 400, but am having a hard time finding a 400 crank to put in my 351m block. I am now moving and no longer have my bronco, so the project was put off. MJ is correct, they have the same valves as a 2v, also as stated in my first post, but with the closed chamber (4v). Now, if someone wanted to sell me a 400 chank, I would gladdly buy it too. For a light truck, ie bronco or an f-series that isn't used to tow alot, I would build the 400 as they are lighter and came stock (parts/swaps are easier) as compared to the 460. Don't take me wrong, but the 460 is a great engine, had one in my 97 F250HD, but it really sucked to just 'drive'. My father had a 77 F250 with a high milage 400 that was tuned and got around 13 mpg on the freeway (no overdrive), could pull a house, and easily smoked 33" mud tires.
 

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All of the specs on the 400 I have ever seen has them putting out about 160 HP at 3500 and about 340 lbs of torque at about 2000. The kinda neat thing about these numbers is that they are exactly 8/6 the amount of power the 300-6 of teh same year puts out. same bore, same stroke, same compression, same everything.

When rebuilding a 400, get an aftermarket timing set, not a stock replacement set. the stock ones and the stock replacements have the cam timing goofy which causes a major loss of power and economy (but somehow or another makes the motor run cleaner ::confused:: ) i know it's off by about 5 degrees, but can't remember if it's advanced or retarded.

One advantage to compression that no one has brought up is the fuel economy factor. If you go to about 9.5:1 you'll see an increase in power and economy while still being able to run on regular gas. If you're getting into it anyway, it'll be worth it.

Justin
 

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the 400 vs 460 debate is a small block vs bigblock debate
if you are building a big block, then of course you start with a 429/460 and stroke it to 557
if you want low buck small block, a C based engine is impossible to beat
what we need is a C aftermarket block that can take the high power the heads can deliver
 

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Didn't SVO (ford motorsports) make an all aluminium c style block? I think it was refered to as a NASCAR block or something.
 
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