First off has anyone on here ever built a 408 for one of our trucks? Ive been reading alot about the 408 vs the 393 builds and their about the same price. the only reason i would go with a 393 is so that i dont have to shell out the extra cash for the .30 over machine work..

the plan is for over the summer to get a 351 block to build and by winter time have it in the truck in my sig. its going to be a street truck for the most part with maybe a little offroad and maybe hit the strip a time or two just to see how it does. so reliability is going to be a big factor.

im really leaning toward the 408 because of the extra displacement and all the other stuff ive been reading about on the mustang forums. but as far as budget goes, from my understanding, you can build a 393 with a different crank, stock 351 rods, and stock 302 pistons. that doesnt sound very reliable to me but hey you never know..

my question is, what do you guys recommend? as always id like to keep the cost as low as possible. what build do you guys recommend? 393 or 408? if i go with either one what all am i going to absolutely have to upgrade? i want something that can benefit from bigger/better parts/upgrades later on. for example can i use the stock injectors, throttle body, truck intakes, and heads on the 408? of course better products of all of those would be beneficial but are they an absolute necessity?

lets hear some input guys!

 

If I was going to build up the 351, I'd go straight for the 408, simply because of the increase in power you will see. And as long as you're going big, you might as well really go big. I'm fairly certain that youre ok with stock heads. not sure about injectors. i think most of the top end will be good to go.
That motor is going to be nuts in a half ton though.

 

If you're doing a rebuild, why not get the cylinders cleaned up and use new pistons? Kind of a waste of time, if you ask me, to try to skimp on boring/honing/new pistons on an engine build like this. Why not just do a stock 351 rebuild if you don't want to pay for machine work?

Also, is your truck MAF? If not, how are you going to be fueling the engine? Conversion to MAF or going with a carb?

 

Truck is a MAF 302 at the moment.

Will the top end parts be alright for now?

J20owner I got to thinking about the same thing earlier. If I'm going to rebuild it then it's going to need honed anyway so I may as well spend the extra cash and get it bored out as well.

What is it with the 408's that I hear about hitting the oil rings or something?

 

Dunno about the oil rings. If I get a wild hair to do it, I'll get something like this.

My truck is SD, so I'd have to figure out something. Would like to keep FI, but don't really want to go through the process and trouble of doing the conversion, but then again, want to stay FI.

As for top end, I can't say. I'm sure you could use the original heads, but they'd end up being your limiting factory, I'm sure. I've heard good things about AFR 185's, I think. That's the number that's popping into my head at the moment. Would want to stay away from head with bigger flow numbers as it would probably end up hurting torque, and that's what we really want for a truck motor(at least I do).


And, as a machine shop buddy of mine has said:

Power
Cheap
Reliable
Pick 2 of the above during an engine build.

Personally, I'd go with the first and third. But, that's me. Also, I'm only in the dreaming stages and continue to drive my 302-4speed truck around. 408 would almost require use of zf imho. Don't think the m5r2 would hold up for long with that much grunt/towing.

 

The stock 5.8 topend parts(heads and intake) are already quite a bit too small for a 5.8 so they're gonna be really restrictive on a 408. That said the motor will run it'll just have a 300I6 powerband which is all kinds of grunt right off idle but it's all over at 3500rpm where the heads and intake become a bottleneck. To do the motor justice you want a complete aftermarket topend like RHS 180 heads and a TFS intake with 75mm TB, and then you need 30lb injectors, an 80mm MAF meter, a high volume fuel pump, and a tuner to make all these parts cooperate. All that means this is not a low budget project, you could easily spend $3000 on the EFI components alone, and after the motor is all built and running the first time you stand on it you're gonna break an axle or toast the transmission so those parts now need upgrades. The idea of a stroker is great but as is often the case it turns into a pretty big money pit rather quickly so you gotta be prepared for that.

 

That was a problem with old 347(302 stroker) kits but it's no longer a concern and doesn't apply to 351 kits.

 

Yeah the 408 is deffinately out..

I was talking with sidewinder on fb last night and got to thinking that a 302 build would be alot easier and cheaper on me. I already have the motor.

What about a 331 kit? I'm really wanting to do some kind of Stroker..

One thing I don't really understand is the balancing.. Do all the kits have to be balanced? I've heard of a few 331's using the stock 28oz balancer?

 

Balancing isn't a bad idea but it's not absolutely necessary unless you're spooling the motor above 6000rpm regularly and for extended periods of time, an unbalanced rotating assembly like all these motors are from the factory are balanced close enough to handle 5000rpm without issue.

Now if you're gonna do a 302 stroker then there's no reason not to do a 347, get all the displacement you can because it'll make more TQ and that's what you need for truck applications.

 

351W swap.