Grabber

In short, an 03/04 Cobra motor can handle upwards of 25PSI without breaking, and/or coming close to that. My .02

FoxGT

If you get that 4.6. Unfortunately there were quite a few variations & not all will hold the same in stock form. Same for the 5.0. Some engines it makes a big difference while one may be safe at 25psi, another variation could be lucky to hold 5psi. Also the psi it will hold will depend on quite a few factors.

JayRolla

Yea I have been tuning dsm's for years now and thats what I do. I was just saying letting you know what stoich on e85 is. I run 16.1 afr at cruise/closed loop. At wot/open loop I run 11.1-11.5 gas equivalent. I have always liked my lean burn tune for gas mileage expecially when I lost 20% gas mileage switching to e85.

I dont know if its just us 4 cylinder guys but Ive seen burnt valves at 12.1 afr's at least on pump gas. But that is at 35+ psi making lots of power. We usually stay under 11.5 to be safe. Plus the dyno doesnt net much gain from going a little leaner. More boost and richer tune always nets more power then less boost and leaner tune.

Hamutoff

WHOOPS I know that but whoops typo, hhaa ha I contradicted myself
forged pistons will last longer than cast pistons under non-optimal conditions

Grabber

I agree with the variations comment.

My old 07 GT, which is still in the family(GF Owns it now) has been daily driven with almost 12PSI. Down to the number, it runs 11.39 PSI. So, depending on the amount of boost, and the setup, the 4.6 2V or 3V can handle as much boost as the 5.0, if not more.