[ERA Chas]

Al,
Below is an article I researched and authored in '06.

COMPACTED GRAPHITE FACTS

CGI falls between gray iron and ductile in regard to material strength. Gray iron’s structure is not as strong as CGI.

The basic difference between CGI and gray iron is the shape of the interconnected graphite matrix. In a CGI matrix, the graphite is more compacted and rounded in what is referred to as “vermicular” or “worm-like” in shape.

When magnesium is added to gray iron in its molten stages the graphite shape changes to a compacted flake. During the casting process, magnesium levels must be maintained at precise levels between .010% and .012% or the casting must be scrapped. The precise control of magnesium is aided when titanium is used as an anti-nodulizing element between .1% and .2% as it increases the ability to produce CGI with higher levels of magnesium. The drawback to using ti is that it creates hard inclusions, making the part much less machinable. The percentage of ti content is very important because a small change in percentage of ti in the CGI can cut tool life in half.

Though not as strong as ductile iron, CGI is 75% stronger and up to 75% stiffer than gray iron. It’s five times more fatigue resistant than aluminum at elevated temps, and twice as resistant to metal fatigue as gray iron. The nodularity and tensile strength of CGI has been found to increase as wall-sections decrease. A CGI block can be fabricated that will be lighter than an aluminum block for equal power densities.

Unlike gray iron, CGI is a very low sulfur iron. Sulfur in iron is a lubricating layer that facilitates machining. CGI doesn’t have it. Compared with machining gray iron, tool life for milling and drilling operations in CGI are half and tool life in CGI boring operations are one-tenth. Machine tool power requirements for CGI are 10-30% higher.

Since CGI rough machines very well, there is potential that some grinding operations may eliminate other semi-finish operations, which in turn will save time in the overall process, and bring the cost down to a competitive level.

Honing abrasives: Honing stones are different for CGI than gray iron. The number of strokes and the abrasives must be tuned for your specific requirements.

The weakness of all V-engines is that there is flexing in the valley between cylinders under power. CGI strengthens this area considerably.

Users of CGI in engine blocks:
Audi, all 2.7, 3.0 V6 and 4.0 V8 diesel. BMW 7 Series V8. Hundai is using CGI in all series production blocks for 2006. Nearly all NASCAR teams are using CGI blocks or blocks with CGI liners. These liners are usually plated with a hard surface coating. Toyota’s Craftsman truck 5.8L V8 is a CGI block that weighs 195 lbs, has .118” cylinder wall thickness and makes 650HP.
12-06


I hope you conclude you DON'T want CGI. Problematic to pour, murder on machining bits and stones and the only advantage from a weight standpoint is if you redesign the molds for thinner wall thicknesses and it will not harm strength. Otherwise it's slightly heavier than an identical gray iron block. It's major advantage is it is extremely resistant to race level stress and heat level cycles which keeps the bores rounder longer. That's why the Hemi and Wedge Super Stock guys want (but can't) get them.

Do you have connections in the casting industry? You will need that and be able to afford the tooling and pattern making for redesigning the FE block to pour in CGI. Unless you're gonna run a season of Super Stock, you don't want to consider this.

Why not a 511 or 527 Cammer FE from the good builders on here?
You can easily have in the 800HP neighborhood but you gonna run that beautiful car like that?

I don't think you want CGI for the lawn chair guys.

Hope you find the info helpful.