If you ever go 2618 forged alloy, be very carefull of this.
Too much clearance with 2618 alloy.
2618 or 4032...these forged alloy pistons are exceptionally strong and run up to 100 deg F cooler under nitrous or turbo conditions than most cast alloy. If 4032 alloy, they are quieter at idle when the engine is cold than 2618 alloy.
Excessive piston slap when cold causes cracking and clearance needs and cost is the only reason you don't see more forged pistons around.
Blair G was on a fast track to Engineering sucess as a Roading and Mine Engineer of exceptional abilty.
I was a year behind him at school, and he asked a boat load of questions when he bought a 5500 dollar engine from the news paper after the NZ saremarket crash. After the engine was built up with the best parts and advice, we sadly scored a bore in an XE stamped 351C NASCAR block in 1988.
It had TRW's 2618 alloy forged pistons but still did 22 mpg, and made insane power in his Beige 1971 XY Falcon 500, with an 8.5 second 1/8 th on his street one wet night. With me on board.
It had a funny ENGINE NOISE noise at 1500 rpm....
We had to downgrade to a standard 1977 Geelong casting 351C, and US Speed and Spares built Blair up a new 30 thou over engine, and valued the scored block as a 60 thou over 1500 trade on a 3500 dollar engine. So lesson here is that the best block is always worth something, even if you score the bores. No 351 C can take 60 thou over bores EXCEPT some the last thickwall XE castings made for Ford USA BY Ford Australia.
In 1997, it got stollen at the Wahi Mine.
I've seen a lot of old beige Falcon 500's around in hedges and in Sims Pacific skips, and I always look for Blairs old Falcon 500. Those square Flacons and the Torino it was based on were exceptionally good machines.
Too little clearance is worse....Blairs had too little clearance.
A very delicate run in for the first 1000 miles if the piston to bore clearances are large. If its very tight, you need to baby it for the first 5000 miles with occassional blats. Its like polishing silver ware. A mixture of hard and fast, and low and slow but always polishing. Your putting the spit and plish on the internal parts, linishing them like and expert.
Piston knock can be eliminated by plateau honing and the bore texture and piston and ring clearnaces make the engine work well long term.
Forged pistons are not a cure for all engine ills...they need a lot more bore, PTB, Torque plate and ring fettling than a stock Ford cast alloy piston to work.
Ford classically bailed on the forged pistons for the 1993 model year after two years of Turbo Carb 2.3 forged pistons from 1979 to 1980, and then, IIRC, 1983 to 1992 in the 5.0 GT HO spec engines. The turbo EFi 2.3 had them from 1983 to 1988 IIRC.
All of them were loud engines, missing the smootheness you'd find in a plateau honed 5.0 Explorer or Mountaineer V8 engine.