I have an 89 RS, 305 tbi. 200k miles

I was looking through Summit's catalogs and I found their rebuild kit for the 1976-93 305 chevy engine.

There are two selections:

#1 - Forged Compression is 8.64:1 Head CC 64cc price 459.95

#2 - hypereutectic compression is 8.39:1 Head CC 64cc price 269.95

what is the difference between sterling hypereutectic and speed pro forged pistions??? the catalog says it depends on application?

 

search for hyper and forged pistons. i remember there was a thread with lots of good information about the 2. chances are though, that you would just go with the hyper pistons. forged are the extremely durable and expensive ones. hyper are stronger than cast, and are great for most applications (its what im using).

 

Make sure you get flat-tops. The hypers in that kit look like they're going to be dished. Your CR should end up about 9¼:1 or so with the right ones.

The hypers are fine for a more or less stock rebuild.

 

This should clear some things up for ya.

"Pistons: To Forge or Not To Forge

Pistons (or slugs as they are sometimes referred to) reside in the cozy inferno under the combustion chamber of the cylinder. Attached to the small end of the connecting rod, these units move up and down in the cylinder at tremendous speeds pushing air in and out of the engine. Most engines, even performance-minded motors, come from the factory with some sort of cast aluminum pistons. There are both high- and low-pressure cast pistons and their resistance in a hostile cylinder environment is relative to the density of their composition and its related resistance to friction and pressure. Simply put, cast pistons cannot withstand the levels of heat, friction, and speed that aluminum forgings, with their denser mass, can survive. Casting is a mass production process that allows for minute imperfections and porosity in the piston. Cast pistons, which are stock in popular motors, are often high-pressure castings with friction-fighting coatings to survive more revs. The advantages of cast pistons are that they’re lightweight, there’s a lower thermal expansion rate compared to forgings, and they cost less. For most mild performance applications, these castings are quite effective due to their lower heat conductivity and tendency to reflect heat back to the combustion chamber.

Hypereutectic pistons became the rage in the early ’90s as they offered the reliability and light weight of cast pistons but were resistant to higher cylinder temperatures. These pistons are cast with a material high in silicone content to achieve the low expansion rate and cylinder wall tolerance of a common cast piston, with near forged piston strength. Hypereutectic pistons are ideal for high-performance, naturally-aspirated combinations that won’t suffer under the strain of power adders like turbos or nitrous, which can quickly decompose this strong, but inflexible style of piston. These pistons are priced in between pressure castings and forgings.

Forging is a process that creates a solid chunk of uniformly grained metal. The details, features and sizes are then precision-machined from this piece to create a near jewel-like finished product. Forged pistons come from the aftermarket in various sizes, pin and ring locations, and dome configurations. Forged pistons signify a serious commitment to the engine’s performance potential; their ability to withstand heat and pressure at greater speeds inevitably means greater outputs than cast pistons. Most forged piston manufacturers offer two different alloys as the base material for the forged pistons. Forged pistons become stable at higher rpms, once their material expands, but can cause noise as they slap around in the cylinder walls at low speed when cold. The aluminum used for forged pistons differs in its proportion of silicone and copper, and thus offer different expansion rates. Additional silicone in a 4032 grade alloy yields a piston with lower heat expansion properties that maintains a tighter piston to wall clearance. Another grade of aluminum, 2618, contains less than one percent silicone with a higher content of copper. The composition of such pistons permit greater expandability and require greater piston-to-wall clearances, making it suited for the extreme heat and pressure caused by high-boost turbos, superchargers and loads of nitrous."

 

Nicely written Article NO4NJUNK. puts things in simple terms about pistons. I hope the moderators will use it as a tech article and put it on the tech board since this is a question that comes up often. Wow guess I should read more of those magazines. lol :hail:

 

I had great succes with my rebuild with these folks too
www.enginekits.com Northern autoparts seem to have some really good products/prices. Although, I havent used them yet.

 

Sorry Radiateu, but I didn't write that. Although a magazine did write it (carcraft). Anyway, I don't think we could post that unless we gave them some recognition BUT that doesn't mean I can't change the article around a little and just stick it on there anyways . I have to give credit where its due.

 

I too believe giving credit where it is due. So why dont you give them credit for righting the article and you can take credit by doing the research. Written by so and so from Car Craft and researched and posted by NO4NJUNK. How does that sound? You should be given credit for research dont ya think. I think rewording it could be misconstrude as plaguerism (sp).lol

 

I can go along with that .

Here are the details...

Moving Parts
Reflections on an Engine’s Reciprocating Assembly
By Bunky-Moe-Funky
Photography: and courtroom renderings: Jughead P. Jones
Brought to you by Super Street

And researched (found) By Brian McClean (AKA--No4NJunk)

Site Link--
http://www.carcraft.com/editorial/ar...=text&id=23480

 

Well..........sounds like you got it my man. See if Vader will place it in the tech bulletin. The next time someone asks the difference in pistons they can simply attach that article with your name all over it along with the Bunky MOE Funky lol now thats funny

 

LOL. Damn....Funky as a last name. Hhaha. Yeah I'll PM him with a link to this post. Well see what happens!

 

LOL. Damn....Funky as a last name. Hhaha. Yeah I'll PM him with a link to this post. Well see what happens!