10

10/03/05

Subject: Rommel “Production” Cross Ram Manifold

Part Number(s): Upper Half – PN# 3941130, Date code – 10-3-68
Lower Half – PN# 3941126, Date code – 1-21-69

Historical Perspective/Overview - General

1967 was the first year for Camaro in the SCCA Trans-Am Series. It was a hard fought season with a single four-barrel induction system as per SCCA rule limits. For the 1968 Trans-Am racing season the SCCA changed the rules from "Not more than one four barrel" to "Not more than two four barrels". This change was largely in response to unofficial factory prodding with the intention of creating a "More exciting Trans-Am series".

As a result, Chevrolet developed and released the "2X4 Carburetor Conversion Unit" PN #3940077 for use with the 302 Z/28 cuin engine. This special "Cross Ram Induction" system was made available over the counter through Chevrolet parts departments as a "Heavy Duty Service" option beginning December 1967.

Cross Ram Components - General

Prototypes: Initially, there were four or five complete prototype units built up inside Chevrolet Engineering slated for performance evaluation. Each of the units was O-Dashed Numbered (0-310510) identifying them as pre-production or prototype components. These prototypes were exceptional in the sense that they would later be used in the SCCA Trans-Am Racing Series on various well-known racing chassis.

Performance evaluation on the first manifolds was conducted inside Chevrolet Engineering by the Product Performance Group and by Smokey Yunick at his shop in Daytona Beach. It was on these first prototypes that specific upgrades and corrections were made in an effort to extract the full potential of the components. Some of these corrections are quite evident and appear distinct from the original casting having been accomplished by hand. These alterations include the critically significant fuel distribution fixes (runners and dams) inside the lower manifold and the addition and removal of material for flow correction.

Production: The production manifold was assigned production part numbers for top and bottom halves and the final configuration of the distribution runners were cast into the lower half. The splash shield that was part of the prototype was dropped as it was determined not to be necessary since there was no heat crossover to vaporize the oil that came in contact with the manifold. The water jacket was in its final configuration and the heater hose outlets redesigned with the 1969 water pump in mind.

Rommel Cross Ram - Subject General Description:

Chevrolet Cross Ram Manifold Assembly

Chevrolet Cross Ram Manifold assembly consisting of lower and upper manifold halves. All components are original Chevrolet built. All appear in excellent, restored condition.

The manifold identified on the cover page and the subject of this document is consistent with the Chevrolet Production Cross Ram units produced by Winters Foundry.

The dating on this manifold is in alignment for its use during the 1969 Trans Am season beginning with the 24 hours of Daytona (2/2/69). The manifold appears to have been used in competition.

History

Bryan Paschal purchased the manifold from a seller in England. It was then sold to the current owner, Joe Rommel in July 2005. The manifold was repaired and restored to original condition.


Manifold prior to restoration	Manifold after restoration

Historical Importance:

This research attempt represents the successful and comprehensive documenting of a significant race bred Chevrolet development. A works in-progress touched by the greatest engineering talents in the world. An effort that changed the course of racing history and facilitated the most successful automotive marketing strategy for Chevrolet to date by helping capture the prestigious SCCA Trans-Am Series Manufacturers Cup for two consecutive years.

In particular, this Cross Ram Unit holds a special place as it consistent with the earliest manufacture of Production Cross Ram units and in alignment for it’s use beginning with the first race of the 1969 Trans Am season.

Manifold prior to restoration in “Competition Raced Condition”

Photographic Documentation


Restored Chevrolet Production Cross Ram Unit.	Underside of the lower manifold showing a casting date of 1-21-69 (see insert).

Top plate removed – Note the distribution fixes were cast into the bottom of the production manifold.	Production Manifold - Note the part number 3941128 (see insert) heater hose outlet, temp sender boss and Winters snowflake, typical of production units. Also note the unusual stamping above it (G W with a IMP inside a circle between the letters).

Production Top Plate with Winters “Snowflake” and part number 3941130 (see insert).	Underside of top plate revels casting date of 10-3-68 (see insert).

Restored Chevrolet Production Cross Ram Unit.

Underside of the lower manifold showing a casting date of 1-21-69 (see insert).

Top plate removed – Note the distribution fixes were cast into the bottom of the production manifold.

Production Manifold - Note the part number 3941128 (see insert) heater hose outlet, temp sender boss and Winters snowflake, typical of production units. Also note the unusual stamping above it (G W with a IMP inside a circle between the letters).

Production Top Plate with Winters “Snowflake” and part number 3941130 (see insert).

Underside of top plate revels casting date of 10-3-68 (see insert).