im thinking about getting a new mustang .. I'm just curious though what the weak parts are on the newer mustangs.. like what will break first in higher hp instances.. like if replacing the pistons with forged ones is all I need, to add 100hp resistance etc..
Some have gone over 600rwhp for a while anyway.. If tuned properly, you could be fairly safe at 500rwhp. The pistons are also the weak point. Tops are ony 1/8'' thick.
I would say the weak point in any stock engine are the rod BOLTS. Forged pistons are a good Idea if you want to make any serious power.
Unless the rod bolts are undersized in a particular engine, the connecting rod itself is BY FAR the most critical component in an engine when that engine is being driven hard. I have seen WAAaaay more rods fail, than rod bolts. This is not to deemphasize the importance of quality, properly installed rod bolts, but the rod itself is more prone to failure.
What is the max safe RPM limit on the stock 4.6 3V V8 that's good enough to hit almost on a regular basis?
The rods in these engines are NOT forged rods as many engines of the past. They are made of metal powder pressed together under very high pressure. Frankly I am afraid of them for much of any consistent high RPM operation. The connecting rod in ANY engine is the weakest link when it comes to high performance, high RPM operation. In ordinary service these rods will far outlast the engine, but you are talking about a different use than grocery getting or even spirited driving. My engine has yet to see the redline. I am sure that it will at one point or another, but it will not be for long and it will be very occasional. If you are looking for reasonable engine life I would not run it to the red line very often and I would NEVER exceed it. I expect that revving it to 5,000 RPM on a regular basis would not risk rod failure, but it will slightly shorten engine life. If you want to rev this engine to the redline consistently, you should STRONGLY consider a set of good aftermarket forged rods. In fact, I see LOTS of posters on this and other Mustang Forums that list LOTS of performance mods. If I were personally going to spend LOTS of time with the engine at red line, I would FIRST put money into a good set of rods BEFORE I started spending money on performance improvers. My $0.02
What's the "redline" RPM? Ford sets the revlimiter to 6250 for the stock GTs but SCT sets it to 6800 RPM.
Theres no practical reason to go through the trouble of tearin into an engine to replace rods so one can hit "redline" on a stock engined 3valve. You can redline it all day stock and not worry about the rods going. They are weak in direct comparison to a forged rod but not made of paper either. Driving a car hard does not shorten engine life on a well maintained engine. ABUSING IT with excessive boost and banging the limiter and mechanically overrevving will on the other hand.
I agree with everyone, The rods are the weakest part of the moter, our shop car is in excess of 600 rwhp with a stock motor, but I would not reccomend for anyone to try it. We tell our customers 450 with a good tune is a nice safe number. If you plan on staying N/A there is no need to replace the rods unless you opt to do something lighter to build a nasty little n/a motor. If you have other concerns in driveline strength the driveshaft itself is weaker than any other part of the drivetrain. In instances of drag racing, (with a sticky tire) the stock clutch can easily out handle the stock driveshaft, next would be the clutch then the input shaft in the trans, then at aome point you will realize a weakness in the side gears of the differential, they will have a tendenciy to crack if you opt to hole shot or wheel hop the car regularly. Don't let this talk you out of a car, in stock to mild form they are awesome and truely reliable, I am just giving you the list of failures in order, that we have logged in the two years we have been racing our cars. If you do not drag race or opt to run a sticky tire you will find that everything will live a long happy life.
