what kind of pistons

what kind of pistons are best, forged or hypereutectic. summit has both for my 350, the forged are more expensive but the others have higher CR's. i know that higher price doesn't mean always mean it's better so what should i go with?


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Forged, they can be bought with the same advertised comp. ratios as the cast hyper. pistons.

Larry

what kind of engine are we talking about? street, drag race? blower motor? stock/mild build?

If this is just a street car go w/ the hyper's if your gona do alot of raceing go w/ forged, keep in mind the forged piston requires more clearence and you hear alot of piston slap when the engine is cold, hyper's use the same clearence as stock pistons.
good luck

yep, depends on application.is it a weekend play toy ? daily driver ? what max RPM do you intend to run? is it going to be normally aspirated ?.
the forged are generally stronger, & lighter, & of course weight can be an issue if you plan to buzz it high. there are differant types of forged pistons to in various weights.
Like mentioned earlier, the hyereutectics are a high silicone cast piston, so they run tighter clearances, means they are less noisy, they well last longer under normal operating conditions, but, you better plan to stay within 6000 RPMs, & if you plan to spray, or use a blower or turbo, stay conservative.
Ive had KB hypereutectics in 3 motors, & was pleased. Its all a matter of intended usage

they are for a 350 that will put out about 450 hp and be used occasionally for drag racing. i can only see 9.72 CR in forged but i was planning on running 10.72 with a Holley systemax top end which requires "Zero Deck" but i really don't know what that means.

wow, the last reply came as i was writting my last one. the car will be a daily driver and i believe the cam is good through 6200 RPM. the CR is up in the air, the kit i wants, page of 115 of the Summit with the willies on the cover, only has a 9.72 CR in forged pistons so how much difference in hp would 9.72 forged pistons have to 10.72 Hyper. i don't plan on running any boost.

hotrod, no offence, but I think maybe it sounds like you need some guidence from your machinist, hed be a good source.
Zero deck means the pistons is at the top of the cylinder. most decks have to be machined to achieve zero deck hieght.
there are plenty of brands & sources for pistons, you can get compression ratios 15.0-1 & up if you want. that 9.72-1 your seeing is most likely with a 76cc head, final compression ratio will depend on the deck hieght, gasket thickness, cumbustion chamber size, bore size, as well as the piston itself

what would a normal 350 be decked at and how critical is this to the performance of the heads and entire engine.

The compression ratio is important, but the deck height being off is not going to affect CR enough to make much difference. BUT, what it can affect is quench distance. This is the distance from the top of the piston to the head when the engine is assembled and running. There is some difference in opinion, but .045 is about the max you want this to be. Any more and you get poor combustion and the engine can be detonation prone.

Most new forged pistons are not as loose as the old dogs. The last two forged piston engines I put together were in the .003 skirt clearance range if I rememeber correctly. They are a little looser around the ring lands, but not like the old school forged pistons. Neither one of my engines has piston knock when cold.

Chris

Turbo is correct about the later forged pistons (although Probe and SRP still run more).

Stay away from the L2256 TRW (Speed-Pro). It is a street piston and will break with too much clearance or nitrous.

tom

My turbo engine was one of the engines I was talking about. It has SRP pistons Maybe some are different??

Chris

SRP clearances are application-specific and depend on whether they are of the 4032 alloy or the 2618 alloy. The 2618 alloy require more clearance.

tom

if i'm not running any boost, or nitrous and if stock rods will be used will Speed Pro work for me? and from a weight standpoint which is best?