06/20/05

Subject:                    Ricks First Generation "Daytona" Cross Ram

Part Number(s):      Upper Half –     PN# 0-310512, Date code – 11-2-67 (No Rev.)

Lower Half –     PN# 0-310510, Date code – 12-8-67 (No Rev.)

Carburetors –   LH & RH - List 4210, PN #3906631-DA/3941140

 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 (0-310510/0-310512) 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 now cast into the lower half. The oil 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.

Rick’s First Generation Cross Ram - Subject 

GENERAL DESCRIPTION:

Chevrolet Cross Ram Manifold assembly consisting of lower and upper manifold halves, first design carburetors, carburetor linkage, fuel distribution hardware, stamped steel heat (oil splash) shield, production high performance oil fill tube, production thermostat housing and plenum style air cleaner. All components are original Chevrolet built or distributed. All appear in good condition.

•  The manifold identified on the cover page and the subject of this document is consistent with the initial or first working group of prototypes produced by Chevrolet. It was among those four or five complete units built up inside Chevrolet Engineering and evaluated for performance by Engineering’s Product Performance Group and by Smokey Yunick at his shop in Daytona Beach.  

• The distribution fixes (made to the manifold floor) were accomplished primarily by gas analyzation methods, that is, obtaining readings by taking samples at the exhaust ports.  Also utilized was the more gross method of "reading the plugs" after dyno runs following changes that were made based on educated guess work. 

This particular area of development was complicated in that an intake port that is rich at low rpm can also demonstrate itself to be lean at high rpm. Needless to say, time spent in this area is crucial for the best obtainable performance results. It was through much educated guess work and extensive trial and error that the final runner configurations were made.

Some flow work occurred simultaneously inside Chevrolet Engineering and it’s interesting to compare the manifolds developed by both camps to observe the variations. The distribution fixes seen in this manifold were hand laid using aluminum wire and aluminized Devcon Epoxy.

IDENTIFYING FEATURES (Specific to Rick’s First Generation Cross Ram)

 Several features related to this manifold make it significantly unique as follows:

• An interesting anomaly can be seen at the thermostat housing on the lower half of the manifold. A mold tab that was typically ground-off on all prototype and production manifolds was inadvertently left intact. This distinguishing feature makes this unit very unique and easily identifiable (See photo documentation).

 This identifying trait in conjunction with the lack of a Winters Snowflake on the lower manifold front intake runner, lower manifold cast date (11-2-67), top cover cast date (12-8-67) and the absence of a revision date (lower and upper manifold) helps to identify this unit as being consistent with one of two units rushed to Roger Penske for use in the ’68 Daytona Event. Component date sequencing and carburetor configuration also supports the aforementioned (See Carburetors section below).

•  In addition to the above, the following are less significant observations related to condition: Two fuel distribution runners are missing from the lower manifold half. The manifold exhibits many surface imperfections and a great deal of core shift typical of a hasty mold/core set-up. The front intake runner on the lower manifold is slightly irregular. The lower manifold bolt-holes are elongated indicating alterations were made to the heads and or it was in-service extensively having been “broken-down” frequently as is consistent with use on a racing engine.

KEY COMPONENTS  -

 The carburetors provided with the subject cross ram package were of the first design, dual feed, single pump, PN# 3941140, identified by List # 4210. They were hand built inside Engineering using production carburetor PN# 3906631-DA. The following gives a detailed explanation related to the Part Number alterations appearing on the air horn.

 Initially, PN # 3906631-DA (List 3810) carburetors were used as the basis to build PN # 3941140 carburetors due to the urgent need for a workable prototype for competition use. PN # 3906631-DA (List # 3810) carburetors were re-built and hand scribed in Engineering to produce the specified carburetor configuration that was later assigned Production PN# 3941140.

 The origin and uniqueness of these pieces is immediately recognizable since they bear Engineering’s telltale “fingerprint” - that being the hand scribed 4210 list number and the obliterated original list number 3810. At the time these prototypes were being developed, the production Part Number (PN #394110) had not yet been assigned, consequently it was not scribed onto the early 4210 carburetors, only the list number was altered and the original PN # 3906631-DA remained.

Therefore, in the case of the early PN# 3941140 carburetors, the list number should always be used as the correct identifier since the early 4210’s (PN# 3941140) were hand built using Part Number 3906631-DA carburetors  (See illustration below) 

The actual production build date of the subject carburetors was the first week in October ’67. The re-build of these units occurred inside Engineering in early November of the same year. The carburetor build/re-build date sequences match the build date code for the manifold and the target release date for the Daytona event.

Carburetor PN# 3941140 (List # 4210) went into regular production (having the proper factory stampings) beginning in March of ’68 (see Illustration above).

HARD FUEL LINES:

Production “hard” fuel lines and distribution block were provided for this Engineering release. The fuel distribution block was altered for racing use, having been drilled and tapped for a fuel pressure take-off at the inlet runner.  This is consistent with the configuration run at Daytona by Penske.

Immediately following the Daytona event, Penske changed the configuration to accommodate soft lines to facilitate quick engine breakdowns and carburetor jet changes (while on the dyno and during events) and to eliminate the danger of fire due to the proximity of the rear most carburetors hard line to the distributor point adjustment door. This alteration was conceived during the Daytona event when much time was lost breaking down the engine to make a repair. To facilitate the soft lines, the carburetor float bowls were switched front to rear, causing the fuel line connections to be outboard.

AIR CLEANER:

Chevrolet Cross Ram Manifold Air Cleaner – First design - Consisting of Filter Element (AFP-22), upper and lower Air Cleaner Plates (stamped steel construction, chrome plated), Phenolic Plastic Plenum Ring and Firewall Duct. Components are original Chevrolet built and/or distributed and appear in good condition.

 The Air Cleaner provided with the subject cross ram package is consistent with prototypical parts.

• Most apparent and noteworthy are the imperfections in the chrome plating left by rods that were silver soldered to the plates in order to suspend them during the plating process. The marks appear on both ends of the top and bottom plates on the inside surfaces. The imperfections left by the rods required abrasive action to smooth the surface after the rods were removed. In addition, the solder interfered with the plating process causing a slight dis-colorization in a “halo” pattern around the affected areas. Production pieces that followed used a different suspension process (magnets) and do not have, to the same extent, the equivalent degree of discoloration and plating flaws.

•  Hard shellac appears on the inside of the Air Cleaner lid around the carburetor stud holes. This material was used as a locking compound and was applied to the stud, wing nut and air cleaner surfaces. All other fasteners (nuts/bolts/pins) used on the engine and chassis were safety wired. This exception was necessary due to the inevitable need to quickly disassemble the Air Cleaner assembly with out too much difficulty but at the same time assure the wing nut would not loosen under the extreme vibrations of racing. This practice was consistent with Penske Racing protocol especially during the 24 and 12-hour events. The material that would have accumulated on the top of the lid (wing nut recesses) appears to have been cleaned off at some point.

•  The lack of provision for a crankcase breather connector is consistent with the first assemblies. All of these pieces were built up and pushed out the “back door” of Engineering to racers to help complete the Cross Ram package. The Cross Ram “Carburetor Installation Instructions” were issued on 3-20-68, several months following the release of these parts. The sheets show the final configuration of the plate with a provision for Air Cleaner Connector to satisfy National AIR Regulation mandates for production. The state of configuration, distinct anomalies and the time of build are consistent with units pushed out to Penske for use in Daytona. Shortly afterward, Penske replaced the Chevrolet supplied Air Cleaner with an all aluminum air box because the flimsy plastic air box demonstrated to be incapable of holding up in competition. 

ENGINEERING USAGE:

•  Evaluation of these components within Engineering consisted of a visual inspection as well as a functional assessment for form, fit and function and was gauged against performance expectations and pre-specifications set forth by Chevrolet Engineering. Therefore, these components would have been fitted and run on an engine dynamometer within the Engineering’s Product Development engine test cell and tweaked accordingly.

• Additionally, it was not unusual for a pre-production prototype or evaluation piece to be pressed into service due to the high demand and short supply of these components.  Often times Chevrolet Engineering and Product Performance would send out what they had on hand to racers/combines who were considered “insiders”. Many of the parts processed through the ‘back door’ were pre-production pieces or prototypes that were clearly marked as such. Due to the specific design state, estimated build time, it is evident that these components were among those pushed to Penske/Sunoco Racing Team.

HISTORICAL IMPORTANCE:

• This research attempt concludes with the successful and comprehensive documentation of a significant prototypical race bred Chevrolet development. A works in-progress touched by the greatest engineering and racing 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, the subject Cross Ram holds a most significant place in Chevrolet / Camaro racing history as it is consistent with the dating and the final configuration of the Cross Ram unit used on Roger Penske's Sunoco Camaro during the '68 Daytona and later events.

Photographic Documentation – Rick’s First Gen Cross Ram 

Copyright Wayne D. Guinn, 2005
All Rights reserved, No portion of this report
may be reproduced without the express permission of Guinns Engineering

www.guinns-engineering.com