I plan on purchasing a custom set of your designed Gibetec mod motor pistons . I have a question if you don't mind please sir.
From reading the thread you created a few years back it looks like the Gibtec's were designed with a center pin vs offset . I was wondering if you could elaborate on the advantages and dis-advantages if any on both styles please. My application is turbo
Second question kind of off topic would be on main bearings will the king MB5281SI matched with MB5219SI for the fully flanged thrust bearing setup work on the Teksid block ? The thread I read over was on a 05+ nemark style block .I assume all aluminum blocks use the same main bearings but that is just a assumption. This is my first 4.6L 4v rebuild so I have been reading alot of threads here on MFF and taking notes. Lots of good info for sure !
When you offset a pin in a piston (other than OEM) one pin boss sidewall will be thinner than the other. See the pic below:
When that happens, the piston's weak spot or probable failure point is that thin pin boss wall. The pic below is a pin boss failure on a piston with an offset pin and one thin asymmetrical pin boss wall.
An OEM piston is forged with an offset pin boss that matches the pin offset so the pin boss walls are the same thickness on either side of the OEM piston's wrist pin. While you can do this when building billet pistons, the pregnant question is why do you want to spend the money to do this? When the answer comes back to accommodate an offset pin, the question arises again but is phrased slightly differently. It sounds like why do you want to use an offset pin.
The only credible response to that question is reduced piston slap at TDC. But that raises another question why do you want to reduce piston slap at TDC, after all it is only a cold start issue. Once the engine is warmed and running, it is inaudible. Detroit offsets the piston pins so new car customers do not badger the service department about the 'sounds' their engines make in the morning when they start them up. A properly sized piston with a reasonable 10W-30 oil will be all but inaudible when you start the engine unless you get crazy with PTW clearances.
Your bearing choices are correct and will serve you well in your build.
Something you should consider is the overbore on your cylinders.
#1 Never bore the cylinders before you have the pistons. Once you have the pistons, bore and hone each cylinder to target minimum PTW dimensions for it's specific piston, especially if it is for a street-driven car.
#2 If the engine is n/a, a 0.020 overbore can be used with caution. Maximum effort n/a engines should be treated similarly to a blown version of the same engine. For Mod Motors that means a standard or 0.005" to no more than 0.010" overbore. The OEM liners are just too thin. They will crack in service, damaging the aluminum liner support behind them, that is, locating the sleeve. After this happens, the block will begin to leak water into the oil pan. You can figure out pretty easily what happens next.
There is a good write-up in the TToC under Engine Build Threads titled "Why You Want to Use Standard-Size Bores". The write-up goes into all the why for and how come on the subject. It is worth your time to read.