Vet76te

This is a question for all you gear / motor heads.

I know that all the old high performance engines came with Forged pistons and rods, (L88, LT1, L82, etc).

All base engines came with Cast pistons.

What was the purpose and reason for the Forged over Cast pistons? Was it simply for endurance, strength, weigth or performance?

bashcraft

Yes.

CaseyJones

All of the above.

zwede

Back then forged pistons had some drawbacks (besides cost):

Since they were loose when cold, there was often noise before the engine warmed up. Oil consumption also tended to be higher than cast pistons.

Today there are "street series" forged pistons that have cured most of the issues. But my 454 does clatter a bit above 2500 rpm before it warms up.

hugie82

Forged can take the abuse of high compression, high rpm, high heat and a shot of NOS. the new Hypertec pistons that pretty much took the place of cast are great for a good street car but if you beat the crap out of your engine forged it the way to go

Indiancreek

Forged are more durable, however, many cast piston engines have been raced. Lots of SS396s during the muscle car years ran cast pistons. The only reason I'd use cast pistons in an engine would be a money issue. If I could afford forged I'd buy them. Honing a block for a forged piston is a little different than for a cast piston.

bashcraft

What's different?

donyue

I believe that the forged pistons were used in engines that would potentially see more abuse than a regular street engine.

Most if not all race/high performance engine builds use forged pistons.

The reasons you have mentioned provide a good summary, however if you chat with an engine builder I'm sure they would have additional reasons to use forged vs cast pistons that the average person might not take into account.

JMHO.

Indiancreek

If the owner is running forged and going to run it harder than normal I'll put two or three extra tenths in each hole. Some guys like an extra five tenths per hole.
The derby guys want even more than that. As they will be run very hot.

Little Mouse

On the 60s/70s OE engines forged pistons added strength and endurance but cast pistons were lighter. Today with different alloys of aluminum in forged pistons you can run tighter clearance and the pistons and pins are lighter. No reason to run a cast or hyper piston unless its the cost driving the decision. Today as in the past the OE manufactures build millions of engines so the cheaper cost of hyper pistons saves them a lot of money on millions of engines built over the yrs.

loup68

I have a ZZ4, Is it true that the 5800 RPM red line is because of the hypertec pistons, that they can not rev higher? Lou.

TheSkunkWorks

FWIW 4032 is the low expansion forged alloy piston. I didn't even give anything else consideration for my 427 high-perf redux.

badrad

Not really, many of GM performance engines today have hyper pistons but don't let it detonate. Hyper pistons tend to shatter into dust when that happens, tune needs to be perfect for the most part so modern fuel injection goes along way towards that.

bashcraft

Engine red lines are usually determined by the limits of the valve train.

76Rat

and crankshaft and connecting rods, but mostly due to the hydraulic lifters.