cast pistons?!?!?!!?

[jveik]

ok just wondering here... if i take a 350 chevy with the lowest of the low stock pistons, cast iron... and throw a blower on top of it... how long will the motor last? 10k miles? 5k? is it possible to use an engine like that for very long?

[Andydg]

I can't give you a real answer and other people probably won't be able to either because there are a lot of variables when it comes to how long an engine will last:

How well have you/previous owner maintained it?
Do you drive like a granny or do you race from every light?
How much boost is this blower making?
Is the CR going to be high enough that it will need to use race gas, but you can only get 93 octane?

Plus a lot more variables that can determine how long an engine will last.

[curtis73]

The problem with cast pistons is that they are fragile. Its probably not going to be an acclerated wear thing, it will probably be a bang clunk thing. So its hard to guess when that will happen. With a properly tuned ignition curve so that detonation never happens, and modest boost like maybe 5-6 psi, it might last a long time.

[534BC]

I would agree, 5 pounds max. Depending upon which "blower" then with some artifitial cooling may push to 7-8 pounds , but risky.

We ran years and years of "truck" cast pistons with 5 pounds of boost and water injection. Hyperutectics are also a bunch tougher than regular cast.
I blew a hole right through the center of a turned down cast piston with slightly over 5 pounds(it was 1/8 inch thick)

[Reed]

I was under the impression that hyperutectics were weaker than cast pistons cause they are injected with many tiny air bubbles (or so i thought).

[curtis73]

Originally Posted by Reed

I was under the impression that hyperutectics were weaker than cast pistons cause they are injected with many tiny air bubbles (or so i thought).

Nope. Hypereutectics bridge the gap between cast and forged. Hyp's are technically cast, but using a drawn method that increases their elasticity.

[nissanfanatic]

LoL

My engine has STOCK CAST PISTONS in it...

[jveik]

yeah i will be using a new longblock 350 4 bolt straight from GM Mexico lol... it has cast pistons, and the cam i was looking at makes the most power at 5700 rpm... however, some web retailers offering the engine list redlines and one said it redlined at 5200 rpm... would this be due to the cast pistons or could i safely rev this engine up to 6000 rpm naturally aspirated with a different cam, lifters, springs, and cylinder heads? a lot of people told me that cast pistons dont like high rpm's so im a little leary of the lumpy cam... i might get its little brother version that makes the most power at 5300 or so and just opt for more torque down low

[534BC]

There's nothing wrong with using cast pistons for high rpm. It is the heat that does it (pressure indirectly)

[nissanfanatic]

What dictates max RPM is piston speed. Look it up. There is a formula to find it. The type of pistons you use have absolutely nothing to do with it.

Other things that influence where to make your max RPM are valvespring strength, port size, manifold(s) design, cam profile and other variations that determine where maximum power is. It would be rather foolish to spin your engine to 7k if power begins to drop after 5500...

[Black Lotus]

Originally Posted by jveik

it has cast pistons, and the cam i was looking at makes the most power at 5700 rpm... however, some web retailers offering the engine list redlines and one said it redlined at 5200 rpm... would this be due to the cast pistons or could i safely rev this engine up to 6000 rpm

The stock cam and valvesprings are likely the reason for the 5200 RPM redline. I would feel comfortable revving a fresh crate engine to 6K, as long as the valvetrain was up to snuff.

[jveik]

so basically, the bottom end can take the 5700 rpm just fine, its just stock spec. cams and valvesprings that float easily that force the redline down??? what is the highest i could likely rev the bottom end before it became the weak link in the chain if ya know what i mean, or basically, what rpm level would i risk throwing a rod or scuffing a cylinder wall or something? for the sake of being thurough, lets assume compression of about 9:1 if that makes a difference

[534BC]

short block, I would say if it is a 350 then 6600 rpm. Depends really on which one though as you can get steel crank and rods and 4 bolt mains, ect. and go much higher.

[jveik]

yeah all i know is it will be a four bolt block with cast pistons... im assuming that the crank is also cast on this particular engine, and the rods are probably bottom of the barrel as well... but hell, who needs to go over 6000 rpm in a pickup truck anyways lol

[UncleBob]

cast pistons are fragile, but that doesn't mean they are a fuse waiting to burn out and blow up, that means they are very sensitive to tuning. You MUST have a good tune to make them live (honestly, you MUST have a good tune anyway with forced induction). Detonation is the killer of all pistons. This is still true with cast pistons, it just takes less detonation to kill them.

I've ran as much as 25psi with cast pistons on race gas. 17psi with pump gas. Its all in the tune. (and setup of course, no matter how well you tun it, if you try running 17psi on pump gas with a 12:1 CR engine, won't matter how you tune it, it'll pop)

And some of the highest reving engines made today are cast pistons. That isn't the limiter to RPM. As mentioned, piston speed and valve train capability are the two biggest factors.