Hi guys, I have a 79 f250 with a 400. Supposed to have a np435 but the op installed an nv4500. In addition the new trans he also uograde to a wieand intake and a edelbrock 4 barrel on it.
What kind of power could I expect out of this? A big jump over stock? I only ask because as it sets now it's very out of time, idles very high, old spark plugs, old distributor and dirty air filter.
Also, the smog crap has had been disconnected, the mounts are also broke on it so reattaching hoses won't be happening. Is this is a bad thing? Will reconnecting the all the smog stuff help me? How much of a gain would I get out of getting some long tube headers or a better timing chain?
No camera, I would provide pics if I could. Crew cab, long box, white, chrome 17" wheels. Thanks in advance. This sight has really educated me in my truck and this motor. Just wondering if I'm gonna NEED a new cam and higher compression to get anything out of her.

 

The intake and carb are worth some HP/TQ but ya didn't mention anything about the exhaust.

'Sounds to me like it needs to get running right before guesstimating power output.

 

Even after a full tune up and getting all the smog stuff back on and with the alum intake and carb....bottom line NO do not expect alot of HP.

Get all the other stuff fixed BEFORE you go cam hunting.

 

The exhaust is two 2.5" tubes that flow into 2 chambers under the passenger seat and then stop right above the back axle. I'm assuming this wasn't stock.(was like that when I got it). I already have the plugs, distributor, and it filter. Waiting on a buddy to loan me a timing light. Do I need to get all the smog stuff back on? I don't legally have to but would it benefit me?

 

I don't see how disconnected smog equipment would make it run worse unless you have vacuum leaks as a result. An edelbrock 4V carb in good condition should run really well. A NV 4500 gains you an overdrive gear to lower your rpms while cruising on the freeway, but doesn't add any horsepower. If you want to accelerate on the freeway, you'd be dropping it into 4th gear (equal to 1:1 ratio of 4th gear in the NP 435) There might be a weight benefit from the NV 4500 over the NP 435. I'd be looking for vacuum leaks, check the timing and jetting/metering rods in the carb.

I've taken the smog equipment off my 79 351M and it hasn't resulted in it running worse.

 

From the factory, the 351M/400M had 170HP +/-5HP. By adding just an intake and a 4 barrel carb, you add about 15 more ponies, at most. By removing the smog system, you do not lose or gain anything, maybe 3-5 more horses but that's a maybe. The cam is what kills these engines, they are 18 degrees retarded for emission reasons. I installed a Comp Cam (CC) 268H camshaft, CC valve springs and lifters, Ford Racing roller rockers, Edelbrock Performer intake, Edelbrock 1406 Carb, Flowtech headers, 2.5" from headers to single 3" to Magnaflow muffler with dual 2.5" tail pipes. When I had the heads off, I used my Dremel to clean and smooth out the ports just a little. I now have between 250 to 275, if not more. Also, the pistons are low compression 8:1, for more emission reasons. I would look for as close to 9:1 compression pistons if a rebuild is in your future. That will add about another 30 horses. Don't bother reinstalling the smog system, it isn't worth it. If there is a smog plate under your carb, remove it. That is most likely the reason you are having the issues you are having now without the pump installed. I hope this helps you. Good luck. BTW, I am a little jealous of your 5 speed, I got the C6 auto trans and at 60 mph, my engine is screaming for another gear. Doing a lot of research for a ZF5 swap.

 

pretty darn snappy. Bought it from Oregon sight unseen from original owner earlier this fall. He claimed power train was rebuilt about 10 years ago. Potential buyers claimed they were worried it would not pass emissions locally. I made the deal and had it shipped to KS. I was curious why he would sell a black XLT Ranger Highboy he ordered new in '76. He claimed it just didn't get driven. Well I found the engine warranty registration in the glove box. Rebuild was done in 2002 and there was less than 800 miles put on it in the last 12 years. I have no idea about the internals, but it has a four barrel, aluminum intake, and headers. 0 emissions. The ole guy says diffs are stock, but it will roll down I-70 at 80mph with C6. I would like to dyno it cause it has more oomph than my other 400 did or a couple 460's we ran. I had never ran a pickup with headers before, so I am convinced thats where the power comes from!

 

My 400 has a basic rebuild that is about 8.8:1, cheap summit truck cam, performer intake, holley 750 dp, mid length headers, and fuel and timing optimized. It made 242/355 on a loaded mustang chassis dyno through t18, 205, d60, and 32" tires.

I figure around 325/450 at the crank.

 

I did the swap to a ZF 5 out of a 92 F350 4x4 the photos were on here it is the best thing i have done for this truck (79 F350 SC 4x4) also put in a timing chain and gears for a 71 351 cleaveland 2nd best thing i have done really woke up the 400 already had headman through the wheelwell headers with 3 inch exhaust through 1 chamber flowmasters and an edelbrock performer carb and intake

 

I would get it running right, then do a timing set upgrade, the headers help some if the rest of the exhaust is free flowing. carb and intake, never seen substantial gains on my 400s, but if you up the CR it should benefit from the bigger carb, cam and valve spring swap would help even more, good luck. Power estimates? Well I would say that depends on your elevation, the condition of everything else, how it runs otherwise, and the way everything is tuned, timing, carb, all that good stuff.

 

I agree with the other guys insofar as getting any 'issues' under control before looking to increase power. If you have system failures, regardless of how small (i.e.: vacuum, poor electrical, etc), they're going to drain what power you do have, and even more so with power adders. SlikWillie is dead on the money that the stock cam is one of the major reasons for lower power in these plants. There are other reasons too, but those can be remedied with the standard buildup for the 400.........the general list includes, 4bbl carb, good intake, good cam, 'straight up' timing kit, and headers........those items will make a major improvement, provided all other ancillary systems are running at optimum. Further improvements would require good heads, machine work, better ignition, better distributor....basically, the works.


You'd do yourself a huge favor by getting really familiar with the 335 engine family forum here, as that's the basis of most discussion there. You'll find that Tim Meyer is a major guru on these engines, and he's a very helpful guy.


Now, all that being said...........if you decide you want to lose your mind like I did, you can get quite a bit of power out of a 400. Mine is stroked (434), runs just short of 11:1 compression, and turns 504 hp and 544 tq........but be warned.........it'll cost ya. How much?...........I won't get into specific numbers as everyone does things a little differently, but in order to get those sorts of numbers, it'll cost more than it would to build a 460 to get the same output.....simple fact. In the time I've been reading here, and from my own experience, my guess is that you can build a 400 to about 400-425 hp for about the same money as it would be for a 460 for the same numbers, but that's where the similarities end. I think that's the 'magic line' where cost is equivalent............anything higher in horsepower, the 400 starts to get expensive, but the 460 remains manageable.


I could always be wrong, but from the numbers I've seen produced, and the cost involved for obtaining those numbers, that's the picture I've seen. Anyway, it's all academic at this point..........as I said before, I agree with the others that you should get your plant running as good as it can before upgrading parts. You'll avoid power robbing issues, and you'll get your money's worth when you do add upgraded parts.

 

I understand building the 400, I've actually already been looking at cams, head work, and 9.1 comp Tim Meyer pistons. I've also pondered just swapping in a 460. Then I could build that over time and maybe a little easier.