SixtySix

I predict the deafening sound of crickets for this thread

70MACH1OWNER

Hi Jeff,
While I cannot give you direct info on the 05 GT 4.6 I have VERY personal knowledge about supercharging a 4.6. I had a 96 Cobra that I put a Kennebell supercharger on. The engine was completely stock. I ran a 6 lb kit for 2 years without any problem. Like all motorheads I wanted more. I raised the boost to 8-9 lb. kit. It was on the car for 2 weeks when I made my 1st and only pass down the 1/4 mile. That 12.5 seconds cost me $6,000.00 and one real pissed off wife. I knew I was in trouble when I went thru the lights sounding like 25 lbs of nut and bolts thrashing around in a metal trash can.
After tearing down the motor what I found was awful. I had 5 shattered pistons from the ring lands up and 2 pistons broke off at the wrist pins, which in turn punched holes thru the block.
For those that may not know that motor has a forged crank, powder metal rods and hyperpathic (this is how they should spell it) pistons. The pistons in these motors are the weakest link. While they are great in stock application for 200,000 miles they are worthless on a blower motor. I rebuilt the motor with forged components from Manley and it is still running with 8 lbs of boost to this day.
I personally believe that the Ford 4.6 is an awesome engine in its stock form and the Kennebell Superchargers are the best. Bottom line is never exceed 6 lbs of boost on a stock motor. And if you feel the need for speed then yank to motor and build it with forged stuff. It is also a must to run the best gas possible. 93 octane minimum.
What happens when you up the boost is the engine starts to detonate. At WOT it is like hitting the top of your pistons with a sledge hammer. The stock cast pistons and rods can't take it. One 1/4 mile run was all it took for mine. I should have been running 100 octane for that boost level but could not get it at the time. Bad decision on my part. And by the way the computer and the knock sensors cannot react fast enough to back the timing off when this detonation starts. I check my computer to see if it had any codes for detonation and it was clean. I learned the hard way as most of us do. Just be careful. If you search the net for 4.6 Mod Motor blow ups you will find it happens just like I decribed above. ALOT!!!!
70Mach1Owner

manystangs

Ouch!

2005MustangGT

8-9 pounds of boost did that? I've seen stock cobras w/ 12 lb's of boost as daily drivers...and have plenty of miles on them. I've seen some get greedy and blow them up too, but never running only 8-9lbs of boost.

S197 GT

Sad story. Looks like you went too far with this one.

70MACH1OWNER

2005MustangGt
I am assuming the stock Cobras you are talking about that run 12 lbs of boost are 2003/2004 Cobras. They have forged guts from the factory. 1996 thru 2002 Cobras are not forged guts. Neither is the 2005 GT 4.6 Put 8 or 9 pounds on one and you playing with a bomb. When you daily drive you are not at WOT thru all gears all the time. Thats when they will blow.
70Mach1Owner

adrenalin

and the crickets are back........................

O5GT

i say we wait and see when one blows up... if one blows up


NOBODY here can decide if they can/cannot handle boost, just because something looks and sounds weak doesnt necessarly mean that it is

so until someone blows one up/doesnt blow one up, i think all we should hear is crickets....or BS

woody1

B) Feelings aren't facts and are difficult, if not silly, to use for good engineering decisions ... especially if you have to later validate why

FrankBullitt05

WARNING: GUT FEELING

If I remember correctly, the 3V 4.6L can only handle about 8 lbs of boost before running into problems... this goes to the material the pistons are made from and the geometry of the mechanicals...

There is a much older thread concerning this from a while ago that got into some technical detail...that's about the best I can do at 1am

70MACH1OWNER

GOFISCH,
You are correct. It is not an 05 3V engine story. But this is fact. The pistons are the same hypereutectic junk that was in my 96 cobra. This is the weakest part of the internals in the engine. I am just tring to save you guys the grief and expense I when thru. It really doesn't matter what year the engine is. It is a matter of good engine building science. Remember, all I am saying is keep the boost down to 5 or 6 lbs on a stock motor, run good gas, and you should be fine.
By the way when Ford builds a blower motor for the Cobra and Lightning they use forged internals. Wonder why???
I would also suggest you make a call to someone like Sean Hyland. He has made a mint replacing short blocks for people that made the same mistakes I did.
70Mach1Owner

angcobra

GOFISCH,
Give it some time, there will be some of the 05 GT engines to be broke. If it can be done, (and it can) it will be done, someone will want just a little more. Heck you have heard of 03/04 Cobra engines and plenty of GT engines to be broke before. From all I have read the weak link in previous GT engines has been the pistons and the 05 GT pistons are even more of a weak point for SC engines. Most likely you could take an 05 GT engine put 5 or 6 psi boost, tune it good, drive it nice, and have it last for a long long time. But, take the same engine, put 10 psi boost, don't tune it, run it WOT on the drag strip, and trailer it to the shop.

70MACH1OWNER

AMEN GLENN!!!! :worship: :worship: :worship: :worship:

70Mach1Owner

mr black

My understanding is that the ringland on the new pistons have stainless steel inserts, and that the top ring is a different sort of material. May make a difference.

angcobra

My understanding is that the ringland on the new pistons have stainless steel inserts, and that the top ring is a different sort of material. May make a difference.
[/b][/quote]

We need to get someone who knows for sure in here but, I read a thread where they were testing some aftermarket SC on the 05 engine and the piston design was discussed. It seemed to me that the ring location was also different from the top of the piston which created a worst condition and the only saving grace was the mods you spoke of. That thread, hosted by the car owner the SC was installed on, warned of the pistons as weak link and limitations of boost to 6 psi.

MJC302

Sorry to beat the dead horse again but 70MACHI is correct. The new pistons have additional silicon in them above the 'eutectic' point of the alloy(12.6%). This causes the brittleness to go up by 40% on these pistons. The higher silicon content lowers the density of the piston alloy(2.33g/cm3 vs 2.7 for pure aluminum), increases wear resistance and make the alloy more fluid for casting, but at the expense of easier catastrophic failure. My 2 cents as a Mechanical Engineer.