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S.B.Chevy Q-Jet base plate & intake modifacations for Gas Mileage?

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AHotRod:
Cliff,
Last Wednesday I ordered a SR-Kit for a Q-Jet #17059203 which is a '79 Corvette 4-speed unit that I'll install on a factory GM aluminum Q-Jet intake manifold, which will go on my daily-driver Model A Coupe.

http://i267.photobucket.com/albums/ii283/LimeSqueezer/PurplePounder016.jpg[/img]]

When I ordered a bag full of parts from you to build a Q-Jet for my Chevy II Wagon a while back, I also bought your book which you autographed for me, Thank You.  Excellant book.

With gas prices continuing to go through the roof, I decided 2 weeks ago to change to a smaller camshaft, tighter torque convertor, Weiand dual plane intake, and all I had around that was ready to bolt on was a Barry Grant 650 Demon  >:( which produces 11-12 MPG each day on my 65 mile round trip to work.

http://i267.photobucket.com/albums/ii283/LimeSqueezer/SparkPlug001.jpg[/img]]

Since aftermarket dual-plane intake manifolds are seperated and sealed, I studied the GM intake and the bottom of the carb.

http://i267.photobucket.com/albums/ii283/LimeSqueezer/QJet001.jpg[/img]]

The areas that I point out are not allowing the intake or the Q-Jet to be totally sealed from side-to-side. My thoughts are to use Marine-Tex and fill these areas.

http://i267.photobucket.com/albums/ii283/LimeSqueezer/QJet005.jpg[/img]]

Here also ....

http://i267.photobucket.com/albums/ii283/LimeSqueezer/QJet004.jpg[/img]]

And here .....

http://i267.photobucket.com/albums/ii283/LimeSqueezer/QJet009.jpg[/img]]

And I planned on using the FelPro 1905 4-hole gasket shown here in the middle ....

http://i267.photobucket.com/albums/ii283/LimeSqueezer/QJet002.jpg[/img]]


Will this work? 

Should I build this carb as stock? .... or follow one of your recipes.

Here is the run down on the Coupe:
Weight: 2530 w/driver
Rear gear: 3.55
Rear tires: 28" tall
Convertor: TCI - acts like stock
Engine: Chevy 355 
             9 - 1 compression ratio
             Hyd Roller - .462 Int. / .470 Exh. lift with 1.5 Roller Rockers
                                 210* "  /   215* "  duration @ .050
                                 Lobe Centerline - 110*
                                 68* overlap
             Vacuum @ idle - 17.5 "
             World Sportsman II heads w/2.020" int. valve / 1.600" exh. valve

The majority of my driving is between 50-60 MPH, or 2200-2700 RPM cruise speeds.

I really would appreciate your ideas, thoughts and comments before I recieve the kit from you so I can do this correctly.

Best regards,
Glenn

Cliff Ruggles:
I would not block the tranfer areas between each side.  I've never found any advantage anyplace doing this, and when I tested spacers a few years ago, the 4 hole spacer provided the worst results everyplace. 

It woln't hurt anything to let one side of the dual plane intake see the other side, and there may actually be a few benefits from allowing this to happen, much like adding an "H" or "X" pipe in the exhaust system ahead of the mufflers.  In the intake manifold specifically, the air to each cylinder stops for an instant when the intake valve closes, much like getting a door slammed in your face.  This puts little shock waves into the incoming air stream.  It may help distribution, and airflow to allow one side to see the other to minimize their negative effects.  I'm not sure about all this, but I do know it has an effect on power output, and may effect efficiency and fuel economy as well?

The dyno and dragstrip testing we did a few years ago with intakes/spacers showed more power and quicker ET with more MPH with a small cut-out between the secondaries.  We saw benefits as well with a semi-open spacer, solid across the front and open between the large secondaries.  This testing further supports letting one side see the other side.

Another thing not to do is remove the entire divider on dual plane intakes between both sides.  Right on the dyno we saw a BIG drop in mid-range power and torque doing this, with only a couple of additional HP at really high rpm's benefit.  Maybe too much of a good thing?

In any case, it's all about application, and the total combination of parts, etc.  Keep us posted on the testing, and the results.  You will find that the APT system in the carburetor will allow you to have full control of the A/F ratio at light load/part throttle.  With the triple venturi area in the carburetors primaries, the fuel milage will be considerably better than any Holley or Holley "clone" once you nail down the best setting(s)......Cliff

AHotRod:
Thanks for your reply Cliff,
Based on the information that I gave, should I follow recipe #1 on this carb for daily driving?
I'd preferr not to run a choke on the unit.

Also, I was planning on not blocking the heat crossover so as to heat the intake and achieve better atomosation which should yeild a increase in fuel economy.

Comments?


Glenn

Cliff Ruggles:
I don't have a choke on my own carb, for at least 15 year now, and don't even miss it.  If it sat outside in a snow drift and I used it in the Winter months, it would have a choke on it!

Good idea to leave the crossovers open.  This shortens warm up times considerably, and helps atomization of the incoming air/fuel charge.

Even with the crossovers blocked off or missing, the intake eventually heat soaks anyhow, just takes a LOT longer.

The heads on my new engine don't have crossovers in them at all, and it takes a LONG time for the engine to warm up in cool/cold weather.....Cliff

omaha:
I cant believe that fuel milage is that bad with a vehicle that weighs ~2600.  I would suggest keeping the crossover also. Id  run a 190 thermostadt, to see what might help. Q-jet and jetted correctly and correct curve in the distributor, I would think that you would get at least 16-18 (or more??) at that rpm.
Oh well, must be neet to have a daily driver like that, do you drive it in the rain too??  Nice ride!!

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