I have a '79 F-100, reg cab, 2wd, c-4 auto trans with a 351M that was bored 30 thousandths(I think this makes it 404ci). My idea for my build is a stock lightening version of my truck if ford had built one. I don't want to sacrifice ground clearance just for better handling because I still use it as a truck. My understanding is that in '79 all of the F series trucks are the same truck except for drivetrain and suspension. My question is has anyone done or have experience with putting f-250 or f-350 stock springs(stiffer springs that are same height) on smaller/lighter trucks? Any adivce would help and this site seems like my new favortie place!

 

"with a 351M that was bored 30 thousandths(I think this makes it 404ci"...

Oy, ya better check your engine math! It'll only be around 354 cubes.
Engine Displacement Calculator

A Lightning? Stiffer springs are only part of the equation and will only make it ride stiffer. Stiffer springs on lowered vehicles are intended to provide linear (and predictable) weight transfer and limit suspension travel.

...the suspension needs to work as a system so springs, shocks, tires, wheels, center of gravity, swaybars, bushings, camber, caster, etc.

 

Thanks for the displacement calculator, but it told me it is 402.7ci. Stock the 351M had a 4" bore and a 4" stroke. I plan on upgrading the sway bar and replacing all the bushings with new red polyurethane ones but I am unsure as what to do about the springs and shocks. Do you have any suggestions?

 

400 = 4 x 4.

351M = 4 x 3.5.

What tire and wheel are you running?

 

A 351M is 4.0 bore by a 3.5 stroke. Run your numbers again.

Bilstein shocks and stock springs + sway bars. Get bushings from Energy Suspension. Fit the widest footprint tires that will fit. The shorter and stiffer sidewalls will provide a faster turn in than one with tall sidewalls.

Still, lowering the center of gravity will greatly decrease roll and improve weight transfer. Not doing so foregoes a lot of improvement in handling.

 

I'm telling you guys it has a 4"stroke. The Cleveland and Windsor are 4x3.5 that's why it's called the 351M/400. Anyways, do you know where our how I can do less than a 3-4" drop? The only one I have found is JDM's dream beam and I really don't want that much of a drop.

 

As far as tires and wheels, currently running stock 15" wheels and 235 by 70 I think. I will upgrade both but want to keep the front and back the same size so I can rotate them. Any ideas on what a '79 lightning wheel would like? Maybe what came on the top of the line mustang lol

 

If I may jump in here a bit. As far as Cubic Inches of Displacement, well it does not matter much to me. You can quote me on this though, it takes an incredible amount of boring to change the displacement much.

I have 3 trucks that I use to go to a job. The road is rough and narrow. Then I jump on the Freeway for 40 miles. The conditions are challenging at best. I have the best luck with adding an extra leaf which is very easy to do and then add overload springs so that when your truck is empty you will be able to keep your molars in tack. Shocks have more influence as the speed increases and can give a nice handling effect. Replacing all the suspension joints with neoprene bushing can be good, but will give a little harsher feel compared to factory rubber. As previously mentioned your tires play a great deal in how your vehicle will ride. I often lower my air pressure as I am driving empty and increase the pressure when I encounter a load. The wider profile tires do not work as well for me as I encounter very rough terrain, but on smooth roads they seem to give a better stable ride. From my experience it will take some fine tuning to get it just right. Having said that it is very important to have all the front end parts nearly perfect. Loose ball joints sway bars and such need to be in great shape for your truck to handle well. Thanks

 

Thanks for all the info everybody. I think I'm going to replace all the factory rubber, get new shocks and make sure nothing is worn out. I'll report back after my experiment with the findings.

 

Respectfully, that is completely incorrect. The 351M/400 are two versions of the same engine with different strokes.

... and a .030 overbore on a V8 does not gain your claim of 53 cubic inches of increased displacement. Is this being told to you (anecdotal) or the result of factual information?

Read the first three paragraphs of this article for info:Hot Rod: 500 HP & 565 Ft.Lbs. from a 400M

Cutting up to one coil is doable, but not advised. Cut no more than 1/4 coil at a time, reinstall, check. Beyond that, camber will be outta whack.

 

Not to beat a dead horse about the 351M/ 400 thing, but I think on the valve cover tag it states 351M/ 400 as the "Engine Family" and stated the CID a little below it. Either 351 or 400. It if you have the 4" bore & stroke, sounds like you have the 400. From what I've heard, that can be a beast of an engine.

Good luck with the build. I started building my 68 F100 into a 1968 Harley Davidson Edition F100, but then sold off the project.