51 8BA NOS block std bore Merc Cam Motor City Alum Heads Alum Intake with two 94 Carbs Progressive Linkage until 60%throttle. The MPG is 12 I think it should be 15 plus. Any tips?
What distributor/ignition? What's the jetting & powervalves in the carbs? What kind of drivetrain & gear ratios?
Progressive linkage with what type of intake? You could be starving four cylinders. Standard bore flatty... want better mileage? Install a one carb intake.
Distributor?? If stock.... Cam...what? Car...what? How heavy? Should be way better unless it'sa dump truck.
Rear Carb is only a secondary on a progressive linkage with the power valve plugged the base has no metering curcuit and the butterflies seal shut. The main carb has an 8.5 power vlave and both Carbs are jetted at #52 on an aluminum unknown intake looks like it could be an Offenhouser close together Carbs with generator. The ignition is Mallory electronic set at 4 degrees advanced. Camshaft is a stock Merc Cam. The transmission is an S-10 T-5 with a .71 final ratio and a 3:50 ratio in the rear. This is all in a 38 Cabriolet. I have checked the plugs and all appear to burning clean and even.
8.5 PV sounds too high, thats the only thing i can think of, and its an easy thing to try. Check your manifold vacuum at cruise and change PV to suit.When you say the butterflies seal shut.. you mean you 'dont even read a vacuum 'shut..,or 'look through it and see no light' shut? that could make a difference, to the PV metering.
Two 2s on progressive really don't work well as the cylinders nearest the primary carb will run richer the the other4. And if they are running lean enough they will misfire and most likely you will never notice it except in mileage.
Run straight linkage on a 2x2. Starting point for sea level is about 47-49 jets & 3.5 Powervalves And your OD ratio is probably .72 (not that there's much difference) which works out to 2.52 overall gearing with your 3.50...
Listen to Flat Ernie. Ernie might be a little stingy on the powervalves, tho. I run straight linkage, 48 jets, 6.5 powervalves, and I have done 22mpg when cruising. Plugging the powervalves is a myth that won't go away. It is unnecessary unless you live in Denver.
Lose a complication for now. Dual system as is could be seen as a crazy mess from some perspectives... Drop the linkage off secondary, make sure it is closed, duct tape top to be sure. Get the thing running on one carb with stock jets and PV. Be sure PV is sealing properly to its gasket where screwed in--many replacements almost cannot seal, because they are the wrong part, and a leak there will dribble gas into base! We can get the thing right easier on the single carb, THEN flog the dual setup. What model 94's? 52 is a little rich, probably at least part of problem. Drop back to 49 or 50. Secondary with no PV is likely close to useless.
Everyone has pretty much given you the direction. The "dumper" carb you with the plugged idle circuit and no power valve is as Bruce said, Useless with your dual carb setup.................but would be a great start on a tripower setup. IMHO
Im getting 25 mpg with the big 1 1/16 94`s .51 jets 3.5 power valves. but Im running a T56 it dose 70 mph at 2,000 rpm in six gear. worth every penny
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