This is a story about a 1976 Chevy, 350 engine, automatic transmission 1 Ton Pickup Truck. It has a 1 ton rear end, i’m not sure what gear ratio is, it’s geared for towing. Rpm is high on the freeway.

For many years it was getting 8.5 miles per gallon with a quadrajet carb. It seems that the Quadrajet carb can’t be grooved, not enough room. With an Edelbrock 1406 and the Groove it got 9 mpg, i knew something was wrong. With help from the Edelbrock tech support it turns out that the fuel pressure is to high with standard fuel pump. With a gauge it tested at 7 psi. Edelbrock says it needs to be less, Between 1 & 6 psi.
With an adjustable pressure regulator installed and set to 5 psi the mileage per gallon increased to 13, WOW!
Even with the Groove the excess fuel just dumped through the system like pouring water through an open window. I bet there are a lot of cars out there dumping excess fuel through their carbs. because of excess fuel pressure!
After Adjusting the jets and metering rods the miles per gallon went to 15, a total increase of 88%.
The mileage test was done at regular surface street speeds. 35 mph stop & go.
From the Edelbrock Carb. owners manual available on line Model #1406 ROD/JET REFERENCE CHART REF# 7 was tried, too lean in cruise mode, ran rough at beginning of throttle. REF# 8 same thing. REF# 5 was tried, it was better but still a little lean at initial throttle.
REF# 21 did the trick,
.095 main jet (down from .098 stock)
.070 x .047 metering rods ( .075 x .047 stock)
Vacuum leaks are critical to fix, i probably have a leaky intake manifold, there is oil leaking around the base. After new gaskets and sealer (a little bit of a job, but not to hard with the help a shop manual) there should be a couple of extra miles per gallon possible.
Wider gapping of plugs still to come, and highway mpg!

Happy Grooving!

This is a GREAT write-up, Chris! I don't know how I missed it when you put it up, but there you go... I guess I AM human, after all!

Score +1 Karma!

Now, how about those highway reports?

Ron

Hi, since I do have the same engine and carb (not installed yet), I would like to know if you tried some other settings or if number 21 is THE one that makes it right for you. Please keep us informed as many othe guys may have that engine-card combination. Thanks. Lapprentis

I 'had' the same Edelbrock carb on the chevy 454 in the RV.

Engine ran great, exhaust emissions were very clean. I already had the metering rods at max and was working on getting the pump pressure down.

I say 'had' because it died not to long ago due to unrelated problems.

Alternator belt took out the power steering belt and ripped a big hole in the lower radiator hose... it wasn't pretty.

I'm pretty sure the combination that Chris came up with will work for any engine using that carb. Getting the fuel pressure down is an important part of the puzzle.

Karl Fortner
Tacoma, Washington

Hi Karl, thanks for replying. Ron already suggested me to go for the bigger mettering rod in order, I guess, to have lee fuel passing through but the 1406 already come stock with the largest so the is no other alternative I am aware of then get smaller jets and uses appropriate rod like Chris did. Here is what I plan to do, pleas your advices are welcome: I will get that combination on the carb as well as a fuel pressure regulator (adjustable) and enlarge the gapping of the titanium plugs I just bought. Since there do not seem to be any PVC or such on the old Chevy 350 (correct me if I am wrong), I will not have to mess with that. Winter is coming in overhere (deep into the worst part of the rust belt), wmy project will be postpone until next spring....Keep in touch Karl and much Thanks.
PS: I plan-suggest to regroup all the Edelbrock related emails on this forum within one common post so that anyone can easily find information.

Hello to all, Chris here. With the main goal to achieve better gas mileage i thought reducing the amount of gas going through the carb and still having the engine perform properly is the goal. The Edelbrock 1406 documentation says the stock jetting is a little on the lean side, already set up for fuel economy, I thought i would push it as far as i could without causing harm to the engine. Which is hard to know for shure, so one has to be careful.

The chart in the owners manual uses a generalized sweet spot graph with pre determined main jet & metering rod combinations to make things easer and safer to the engine.

By reducing the main jet size down one the engine ran poorly at slight throttle ie cruse mode, not enough gas. the engine ran great at idle once it is set properly, keeping in mind the idle is a different source of fuel flow. The engine would stall out with just a slight amount of throttle. slight throttle gas flow comes from the top fatter part of the metering rods in the main jets, as the rods are pulled up by the gas peddle linkage the skinnier part of the metering rods let more and more gas through the main jets, this is the power mode part of the page 22 chart.

After trying a few combinations( at least 5) mostly buying different metering rods and keeping the one down(leaner).095 from stock .098 main jet, combination #21 worked best. The engine is just a tad lean at slight throttle(cruise mode) but i am living with that since the alternative is going back to the stock main jet size .098

Choice #21 on page 22 of the carb owners manual makes the cruse mode(slight throttle) more rich and the power mode(more throttle) more lean. Since i wasn't having a problem with more throttle(power mode) i thought leaning it out would make for better overall gas mileage.
I also installed one step leaner secondary main jets to have even more fuel economy, secondary main jets flow fuel for a lot of peddle to full peddle
I probably have a little less overall power at moderate to full peddle but that still works for my needs and best gas mileage.

I hope this information is help full. It was trial and error, learning how the shape
(profile) of the metering rods moving up and down through the main jets supplies the engine gas at different levels of air intake ie. throttle.

so many variables.

Happy Grooving to all and to all a good night.
Chris

Ps. feel free to ask any questions.

i have another post on a 1999 dodge caravan also