Cast vs forged crankshaft

[The Pope]

Quote:

Originally Posted by Acem I prefer a forged crank anytime I can get one. However think about this. Reciprocating weight slows acceleration. If I was racing I might consider a lighter crank, rods, etc and rebuild more often. I allways thought those lightweight small block chevy components helped them in acceleration. They really kill toughness though. I have a friend with a 2 ton bob truck (ten wheeler) that runs a 350 chevy. He is ALLWAYS having trouble with his engine breaking things. My IH 345 (built heaver than a big block chevy) has over 250,000 miles and is finally getting loose. Both trucks are used on our farms. Thx-Ace

weight though combined with diameter gives a different result. Yes the crank itself has some diameter but the acceleration and decel of the rods and pistons is much worse. Then the large diameter of the flywheel and it's weight. Other things can be done too, under drive pulleys and porting the oil pump feed hole and water pump housing. So you can add a big tough crank and end up with an engine that really accelerates fast.

The other issue is flex, which can cause vibration and other damage the early HP blocks from Mopar had forge cranks and high compression pistons making them HP. NOT THE BLOCK! this is a big issue with many. The blocks don't need to be as strong if the crank flex's less. In the mid 70s though Chrysler blocks got tough, as they went cast inside. Many also vibrate a lot too. My truck 318s have NO DAMPANER from the factory, that's right the lower pulley connects right to the crank with a splash shield. The 318-3 is one of the toughest engines made.

With the 2.2 / 2.5 it was decided the turbo 2.5 would get a cast crank, this is where the thicker common blocks came into being. In an older block though with a steel crank the block doesn't get twisted. Who really knows where the steel CB 2.2 really has its power ceiling.

[GLHNSLHT2]

Quote:

Originally Posted by 4 L-bodies Wow, where did you hear that forged 2.2 cranks are 25 LBS heavier? Maybe 25lbs heavier than a 3 cylinder Geo Metro crank. Take a look at this pic. Not even billet Masi crank is 25 lbs heavier.

Thanks todd, now I've got to weigh my 2.5 crank, 2.2 forged, and Masi crank.

I can lift a bare bottom end 2.5 and 2.2 forged out of the back of my daytona just myself. I can lift them both up onto the engine stand or off the engine stand. But I tore down my masi block on the stand, went to take it off and the thing went straight to the ground. I couldn't slow it down at all.

Weight confusion might also be because of DDG where it says this. "Crankshafts- forged vs. cast. Forged is stronger but weighs 6-7 more pounds more than a cast crank! (The 2.2 16V Maserati forged crank is even worse- it's 23 pounds heavier then a cast crank)""

[The Pope]

you were really out of shape though when that happened