I am considering using English twist snake guides on a 9' 8wt graphite fast action rod(st Croix). I know the English twist is opposite the American twist and the English twist guides are not quite as high off the blank as the American guides. Is there any significant effects as far as casting is concerned
Possibly were the English twist guides developed for there type of fishing or no significant differences.

The English guides were developed for left handed casters, the American for right handed casters.

Seriously, the line will never know the difference. The height difference means the English guides will have less of a twist/torque effect on the backcast although this would be extremely minimal given the overall difference, while the American guides probably offer just a tiny, tiny bit more clearance in the same size.

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From Hopkins and Holloways web site: In years of practice we have found that an English pattern is better suited to a softer, slower action blank than an American pattern which is by far better on a fast action blank. We proved this theory by putting American pattern snakes onto a soft slow action blank in a relatively short time of use the inside legs were showing sign of ware and in fact the Epoxy on the whippings were actually grooved, We changed the guides back to English pattern and tested again, over the same test period no ware was detected.

So much to take into account when building a fly rod and I love it. Thanks for info so far. If any one can add there view point please do.

I use the Snake brand universal guides with great success for years. Gary Loomis' Edge Rods, C.F. Burkheimer, Tom Morgan Rodsmith, and others use them on their rods.