GM Crate Motor ZZ4 / 24502609 or GM Circle Track / 88958603???

[Crate Racers]

Switching from a Dirt Late Model to a Asphalt touring style Modified. Want to get my feet wet before moving up to the touring series. I have read mostly about the 602 and 604 engines, not much about these.

A few highlights out of the rulebook are:

*Engines will be teched according to GM Performance Circle Track Manual
*The only approved carburetors are Holley 4150 series model #6895 and 4150 HP Series List# 80507. Choke horn (model# 6895) may be
removed with a square cut, no taper or bevel, but may not be cut into the body of the carburetor
*Stainless steel, stepped, 180 degree headers, Try – Y headers and multi-merge headers are not permitted. Steel primary tube size of 1-5/8 inches up to 1-3/4 inches outside diameter. Collector tube size of 3 inch outside diameter

Any input would be appreciated! Thanks

[Egoracing]

The ZZ4 will not pass tech if using the GM manual as it is for the 602, 603, and 604. The 603 lost favor in the dirt classes due to the cost was almost equal to the 604 so no one ran it.

[Crate Racers]

That's what I thought but they are very specific about these choices as the only ones that are allowed. I even contacted them to verify. Another great moment for promoters!

http://carawayspeedway.com/wp-content/uploads/2012/01/sm_light_rules1.pdf

[Egoracing]

The 603 and ZZ4 are close but the ZZ4 does not have the oil pan or valve covers and there are cam choices for the ZZ4 where there are not for the 603. For the $$$ I would go with the 603 and use the other money somewhere else.