Hi, I'm new here so I thought I would introduce myself before I tell you about my problem.

I'm 17years old and I bought my 79 F-150 when I was 15. It has a 400M with a Edelbrock Performer RPM, a compcam (212/212 @ .50), dual 2 1/2 exhaust, 4-speed tranny with granny 1st, 3.50 rear-end, and 33' BFGoodrich MT's. Here are some pictures of my baby http://www.geocities.com/azzkickerp51/79Ford/

Ok here's my problem. This truck is a total dog. I can rev it in neutral and the engine has no hesitation, and pics up rpms pretty good. Normal driving is ok, but if I want to light up the tires...it just can't do it. Say I rev it up to 5k (yes I know this is very bad on drivetrain) and dump the clutch, all it does it drop down to idle, sputter, cough, then go. The only way I can get them to chirp is if I rev to 3k, and gently let out the clutch, and all it does even then is make a little chirp. Any thoughts? I've replaced spark plugs, wires, distributor cap and rotor. I've checked my timing, and the mark is just a little above the tab (which is what I was told it should be at this altitude). Now I'm thinking carb troubles, vacuumn leak, or maybe the 400M is just a poor performer. Would a 750cfm Edelbrock carb take care of my troubles?

Ohh, my 0-60 time is 18 seconds, with a top speed of 90mph. Quarter mile time is in the 25 second range. Something has to be wrong here.

 

my pickup had the exact setup...when it had 31s on it, i couldn't keep the tires glued to the road...i put 33s on it, and it did the same as your truck after that....but i think mine still had a bit better acceleration that it sounds like you're having....you could see if you can find a pair of old 31s to slap on the back just to see how it acts then....

 

Did you degree that cam before you put it in? What sort of carburetor is on there? Maybe you could fiddle with jetting and/or acceleration pump to improve off-idle response. Also remember that 33s are much heavier than 31s and they can have a dramatic impact on your performance since your truck has to move all four of them to go (there's no getting around that). By forcing your truck to remain in the lower rpm range longer, where low manifold vaccuum brings about poor atomization of fuel, your performance will also suffer. I assume your truck worked well before the big tires, so maybe all you need is lower (numerically higher) gears. To improve acceleration, you might look at swapping that manual out for an automatic. No reason to keep it unless you are into plowing snow or rock crawling; the automatic does just about everything else bettter than that particular manual, what with the super-long throw and whacky gear spacing.

 

I'm probably gonna open myself up for some hate mail replys,but heres my opinion.I've got a cherry 77 F150 Explorer with a 351M.It is a gas guzzling dog.I think that the 351/400 motors just werent a very good engine,ever.If you had a similarly equipped 460 in your pickup,I guarantee you could smoke your tires-until you broke something in the drivetrain!
I had a 76 F250 hiboy with a 68 Lincoln 460 [360 HP 500 ft lbs torque stock]that would haze the rear tires.
I know I'm not any help,but in my opinion,your not gonna get what ya want with that 400.
[I tell people that the "M" in 351M stands for miserable.]

 

Thanks guys. I suppose it's time to start looking for a 460 and start building it up. The engine runs perfect, but it's just not making the power I want. At least a 400M-460 is a pretty easy swap. Once again thatnks for your suggestions.

 

Don't forget that 68 didn't have much smog stuff on it where as the 351/400 is smogged down to a tiny hp level.

 

I have a 400 , with a c6 auto, I do agree about the 400/351 having low/no power. I have the dual intake, 4bbl, yada yada with 2.75 gears I can smoke em. I actually have to be a feather foot at green lights so I dont chirp the tires. I found my answer in the timing being to far advanced, It sounds like you may be getting all your advance down low, try backing off a little( rotate distributor against crank rotation for advance, rotate with rotation for retard). You can find the direction the distributor turns by taking the cap off and bumping the starter.
Good luck, trial and error yield great results dont give up
http://www.freepicturehosting.com/g/88108_1.jpg

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77'FORD F150 XLT 400

 

OK, i also have to agree...if youre looking for flat out performance, the 400 is not the way to go unless you want to put a lot into it. however, i have a 79 with a 400, c6, 3.5 open rear, and wide 33's. i could break both tires loose off the line for a couple of seconds back when i had a 4.10 posi, and with the new rearend i can leave a cloud of smoke (on turns though.) mind you, this is with an auto, and with your low first gear and "clutch dumping" capabilities, you should have a major tire spinning advantage. to top things off, my 400 is mostly stock with an edelbrock performer and a crappy carter 4 barrel (stock cam). your cam and intake together should work perfectly for 2K-3K clutch dumps. so yes, there is definitely something not right. i also have a truck with a big block and a similar setup, and yes, the power is noticably better...plus the potential (all things being equal) is greater. but as things are, im quite pleased with the 400's performance... considering i get 3 mpg better with it, and it has never given me a single problem. as someone else suggested, timing... check into not only your initial timing, but also try out some different things with the advance, whether that be full, ported, or trying a different port or whatnot. and lastly, not to bash edelbrocks...but i used to dream of owning one some day...thinking it would be the end all to my performance needs, and now after working with three different ones on different cars, have found that the holley's always seem to perform better...but hey, go with what works for you. good luck.

 

The 400 should't be THAT weak .
What gear are you "dropping" the clutch ?
Gears 1 & 2 are not for that ...
Gear 3 is very close to 1st in a Ford car tranny .
Aweful hard on the girl , though ;-)

I ran 4.56 gears with my 351C and 33s out back .
Get her rolling in 2 , grab 3 and nail the throttle ...
used to work many years ago ... getting too old to pay the policeman . :-)

dP

 

I'm dumping the clutch in 2nd. 1st gear (granny gear/compound) I can really smoke the tires in that gear, but I was always told to start out in 2nd gear with these trucks, which I do. I only use 1st for off-roading.

So are you guys doing your burnouts in 1st? If so I don't think I have a problem because I can smokem forever with that gear. But in 2nd...I can only get a chirp.

 

I've got a 78 F-150 351M/C-6. I bought it cheap but whoever owned it before me did a little work to this old horse. It's got full length headers with dual 2" out the sides in front of the rear tires. It's got a cam but maintains the factory intake and 2 barrel carb. It is very torqueee and does not spin tires as much as it buries the speedo. It burns a lot of oil on start up and leaks more while running. The 351/400M is a kissing cousin to the 351C and is capable of satisfying your hot rod dreams. I raced an enduro, "79 firebird with a 400M" stock that set the pace for that class. If your having problems with your 400M you may need to reach into your pocket and ask yourself, "How fast do I want to go". The 460 is a stump pulling Big Block that is great for pulling a heavy 4x4 Ford down the road but the weight and the heat the motor produces are too extreme to drive everyday of the week. If you want your truck to "haul butt" figure a way to get rid of some weight, and if you figure that out, reply immediately, we'll all be waiting!
Kingfisher

 

You might want to pose this same question over in the 351M/C/400 forum. There are a lot of guys over there who have gotten big numbers out of their 400s.

 

Hmmm...that's unusual. I have a 78 4x4 with the 351M in it and I can literally smoke the 31's I have. I have a hard time keeping them glued to the road. I'm getting new ones tomorrow...hehe...and hopefully it'll help going to a little bigger size. Try playing with the timing and carb some. See what happens.