Engine 8 Psi On High Mileage 2 Valve?

Discussion in 'SN95 4.6L Mustang Tech' started by yelowjaket, Dec 27, 2013.


Is 8 PSI (About 360rwhp) safe for a healthy high mileage 4.6L? (With Conservative tune)

  1. Yes it'll handle it fine

  2. No, to many miles....too risky

    0 vote(s)
  1. Has anyone blown up their 4.6L 2 valve combo while running 8psi? If so what was the cause of the failure? Reason I’m asking is I’m wanting to get a 99-04 and run 8 lbs. until I can afford a forged bottom end. But this engine will most likely be a high mileage engine like over 80,000 miles. If it passes a cylinder leakdown test and compression test, it should be ok to handle the power as long as I don’t over rev the engine correct? Combo will be pretty simple to start with, basically a stock GT w/ procharger (Intercooled), injectors, Kenne Bell Boost - A – Pump, 4R70W, and a custom (Conservative) tune on a dyno. Not to be revved past 6k rpm. I know the stock Trans may not hold up but that’s cheaper and easier to replace / rebuild than a motor. So with that much mileage should I be concerned about the engine having 8psi and around 360 rwhp? Assuming it passes the cylinder leakdown and compression tests?
  2. I put a blower on my car at 90k miles. Ran perfectly fine for 30k more miles on 7-8 pounds of boost until some detonation took out a piston. Typically at 450ish rwhp, the rods start breaking. At ANY horsepower level, any significant amount of detonation will break the top ring lands. So whatever you do, make sure the tune is spot on, and NEVER keep your foot in the throttle if you ever hear at detonation. There are other failures, too, like the oil pump going bad or timing chains breaking, but those could happen on a completely stock car.

    Bottom line: get a good tune, keep it under 6k rpm, and it'll live for quite a while on 8 pounds of boost.

    Also, get a transmission cooler and do the J-mod, and the transmission will be perfectly fine at that level.
  3. Right, there isn't anything specific about a higher mileage engine that makes it less tolerant too boost. ANY engine will experience a failure if you get into detonation for an extended period. Like sneaky said, it's all in the tune.
    On my 2.3, I had a vacuum line blow off the fuel pressure regulator. That caused the fuel pressure to drop, and detonation took out the rings on a cylinder. I guess you don't have to worry about that with a 98+ since they don't have a fpr. :p
    Anyway, these engines tolerate mileage very well. My GT has 218k and is still very strong. Only issues you might run into are valve stem seals and chain guides, both of which aren't a big deal to replace. If you want the engine to last indefinitely with a blower, it might be better to keep it at or under 400-425 rwhp and 6k.
  4. Thanks for both of your replies, looking forward to getting back into the mustang scene after a long absence. Good advice and will definately take it to heart when I get this project going.
  5. Since when is 80K "high mileage"? These motors are just waking up at 80K.

    You'll be fine.

    Oh and the 4R70W is one hell of a tough tranny.....I know ;)
  6. [​IMG]

    Been Vortech'd @ 8lbs since 132k miles..
  7. So what's the mileage? I can't read it because of the glare. 175k?
  8. Yep. Hit 175k on a trip to the fam's on Christmas Eve. Put on 600ish miles between the 24th and 25th. And it had just had MM K and CO's installed the week before.
  9. I put my ProCharger on at 95k. Its a stage 2 kit that was supposed to run between 9 and 10 psi of boost with ProChargers bigger intercooler. I really don't know how many psi it was making but it hasn't given me any trouble. I told my tuner to make it safe.

    I just opened up the exhaust, got a bigger throttle body and plenum, installed a fuel pump booster. Just put on a smaller pulley. Going to the same tuner and will tell him the same thing.

    Don't be afraid of intercooled 8 psi. Make sure you have a good tuner and specify that you don't want the car tuned right up on the ragged edge.
  10. Psssshh 90K here and 16psi on a D1SC. Dun be scurred!
  11. Dayum!! You're crazy, man. Doing that on stock internals is brave. You must have a great tuner or a death wish for your connecting rods.
  12. sheit, I run 21 psi on my 240k mile Volvo
    Bob Hughes likes this.
  13. Oops, I should have mentioned that Im forged....so I guess my motor technically doesn't have 90K anymore?
  14. That sounds more like it. I side with the general consensus that 425 rwhp is pretty much the limit of safe operation on stock motors.

    Isn't someone running some out of this world twin turbo on a stock motor. Maybe Tank or somebody?
  15. My biggest concern would be oiling system. That's I believe how my motor got tore up. I haven't taken it out of the car yet so I don't know exactly what failed. If it's tuned right I was told 450 is teetering with disaster. And I tipped on the wrong side of the scale I guess lol. With thst many miles I would consider a new oil pump and check or upgrade the sump. Just my 2 cents
  16. @madspeed...is that 21 psi in your volvo's tires by chance? hahaha
  17. nope, 40 psi there...:lol: