how much psi of boost can the SOHC 4.0 take before something breaks or explodes? and are there forged internals out for these motors?
im going to piece together a turbo kit for my truck to put on once the warrenty is up. the shop where my friends f150 is at right now getting 70mm turbo put on will make the hot parts for me and i have some help from other ppl as far as the intercooler and installation goes. but how much psi could i safely run on this motor? thanks

 

It really comes down to the tune and fuel used.

I've done several turbos on stock motors.

Here are my suggestions:
1) 7-8psi of intercooled boost *max* (4-5 if non intecooled)
2) Go with a smaller turbo vs a larger one because on this type of vehicle will do better with mid range improvement vs top end.
3) Keep the timing and fuel curve conservative. (have it dyno tuned on a mustang dyno)
4) Replace the complete exhaust system
5) Don't skimp on the intercooler. (#4 & #5.. You have a plastic intake and need to get the heat O-U-T of the engine room as well as the intake charge)
6) One range larger injectors (you don't want to go 100% duty cycle at WOT)
7) 180 t-stat
8) One range colder plugs and narrow the gap by 0.005"
9) Switch to a full synthetic oil or one with ZddP
10) Keep the shifts at the stock rpm points and increase the line pressure a little.
11) 93 or 94 octane fuel is a must.

Do those things.. and it'll last.

Rich

 

thanks man! now its just a waiting period ha. would a thunderbird turbo( i think...) be a good size... my buddy is running a 70mm turbo on his 4.6 so i would think something around 58mm 60mm or whatever size around there would be a good choice?

 

The more power you make on a stock ignition system.. the lower the resistance you need within the system.

I'd personally step up to a better plug and even put some dialectric grease the wires connectors.

Rich

 

if you are going to spend the money on a custom turbo, why not spend the $90 shipped for a Screamin' Demon coil pack and then gap the plugs out to .065"?

why not go with a Explorer Express supercharger? with a turbo, you will have to build custom exhaust manafolds unless you put it after the y-pipe under the truck and pipe the air back to the intake.........

 

Given your intended *street* use..
The 4.0L is a short stroke motor which means it's lacking in low end torque by design. Assuming your sticking with a stock long block and stock convertor/tranny...

I'd go with a smaller turbo to decrease lag and make more low rpm power. It'll also limit overall all power and hopefully not push the stock components too much. If we were talking about a drag racing situation.. then I'd go the opposite way.. but risk would increase too.


I'll throw this out there... You really need to look at what you want to do and then make power accordingly.

If your into off roading.. go with steeper gears and put to better use the power you already make. If your into 0-60 blasts on the street *all the time* a small turbo or roots type blower is a good choice.
If your into drag racing from 0-100mph then a big turbo and/or nitrous is a good way. And it your crazy like me.. you'll go with big cubes.. a big blower.. and then nitrous on top of that. (I am building a 800hp Lightning)

IMO the best bang for the buck on a street car is nitrous. Here is my caddy:
http://www.dragtimes.com/Cadillac-El...lip-10711.html (make sure to check out the video too)

Rich

 

ya im still tossing around the idea... i may just go with a small nitrous setup since alot of my friends have it on their mustangs or drag cars/trucks.