FI modified as a tunnel ram on flea. Never saw one like this.

[Jerry G.]

Re: FI modified as a tunnel ram on flea. Never saw one like this.

The spill valve "spills"(back to the fuel bowel) more or less fuel from the fuel supplied by the gear drive fuel pump. The spill is linked to the main control diaphragm such that for more flow as measured by the air meter more fuel is delivered to the injectors.

[Jerry G.]

Re: FI modified as a tunnel ram on flea. Never saw one like this.

Thanks Wayne. Jerry

[Rick B.]

Re: FI modified as a tunnel ram on flea. Never saw one like this.

Clem, you may also want to read through the fuel injection section of the ST-12 and/or '63 Corvette shop manual. Both documents explain the basic operating systems within the Rochester unit. The mechanical fuel injection SAE paper published in 1957 by Dolza, Duntov & Stoltman has all the theory and formulas that explain how & why the Rochester system works. I do not know if the SAE paper has been copied to a website, but I could make a paper copy if you're interested.

One question for you. As this thread has developed, it is apparent that there are at least two ways of adding a second air meter to a late model unit. The first (and easier I believe) uses an adapter plate in place of the ribbed cover with the air meters mounted on top of a common plenum, positioned over the two groups of four intake runners, i.e. early Bill Thomas design. The second method requires machining away some of the plenum height and creating two separate adapter blocks matching each air meter with four specific intake runners, i.e. Gulf Oil & Grand Sport. One of the previous posts showed an abrupt power drop off at high RPM with the Gulf Oil design, apparently when the maximum air flow potential of each air meter is reached (feeding each group of four cylinders). Wouldn't high RPM power be slightly improved with the "common plenum" (early Bill Thomas) design as each cylinder filling event would be drawing air through two air meters instead of just one? On the other hand, I would suspect that throttle response would be better with the Gulf Oil design because the plenum volume is significantly smaller than that of the common plenum design. The Gulf Oil system would be approaching the throttle response of a Hilborn or Enderle (individual throttle per runner) fuel injection system and throttle response is key to fast laps on a road course.

[Clem Z.]

Re: FI modified as a tunnel ram on flea. Never saw one like this.

thanks for the reply and i do have have the 63 shop manual. i will check for the SAE paper on the net. Thanks again

[Clem Z.]

Re: FI modified as a tunnel ram on flea. Never saw one like this.

The spill valve "spills"(back to the fuel bowel) more or less fuel from the fuel supplied by the gear drive fuel pump. The spill is linked to the main control diaphragm such that for more flow as measured by the air meter more fuel is delivered to the injectors.

jerry if you think the over pressure of the pump is breaking the cable what about a external oil pump spring loaded type pressure relief valve located from the output of the geared fuel pump dumping back into the float bowl ?? BWTFDIK as i am not a FI guy