Carb problems

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93toyota

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I am having problems with 8.5 mpg. Also my car will just cutout sometimes and die after it is warmed up. I have a 71 duster with a 30 overbored 360, kb107 hyper pistons, moly file fit rings, stock 308 heads, eddy rpm air gap, eddy 600 cfm manual choke mechanical sec's, new volt reg., new water pump and dist, carter fuel pump, new hv oil pump and pickup. The block was cleaned and magnafluxed. Rebuilt with new bearings and plugs, crank regrind and rods, and then balanced. It also has a a-230 3spd manual with 8 3/4 rear end w/ 3.23 open diff.
The car has since been changed to 2 stages lean on both the cruise and power mode. The problems with the cutting out started then but not the mpg. Never have i had wet plugs and i got about 3000 on the new motor. also the motor is a 1990 and has a stock hyd roller cam and lifters. any help will be appreciated.
 
went 2 stages lean awhile back and mpg has not changed. went to 1 stage lean and now it pops when let off throttle or down shift
 
you should get better than 8.5 mpg if you never leave 1st!
did you rebuild the heads along the way? the new popping could be a header or exhaust manifold leak. What temp does the engine run ? and have you checked out the ignition, the coil may be getting hot.
 
For what it's worth, I was having the popping when I let off or shifted, it was a header leak issue--specifically, I had blown a little piece off of the back end of the gasket. I was also having engine cutout issues but only in the rain.... All of the little problems were resolved once I firgured out part of the gasket was gone.
 
the headers are hedmans so probably a gasket.I can hear the ticking from in the car so I know it has a leak but I still have a carb problem. I think that I need to advance the timing and check it out, plus I am going to reset the caarb to fact specs. Did I mention the carb is a mech secondary?
 
I was having significant troubles with my 6-pak and couldn't figure out why I was fouling the plugs. One day it would run fine, the next day it would run crappy. A 50 cent grounding strap fixed all my problems. Turns out that electronic ignitions are real sensitive and require a good ground.

As far as changing jets to improve gas mileage, unless you are full throttle all the time, changing jets won't make a difference (unless you go so small that it restricts fuel flow at part throttle and then you will be way to lean during WOT).

Recently I had trouble with popping through my exhaust. I was running on 7 cylinders because of a defective spark plug.
 
93toyota said:
the headers are hedmans so probably a gasket.I can hear the ticking from in the car so I know it has a leak but I still have a carb problem. I think that I need to advance the timing and check it out, plus I am going to reset the caarb to fact specs. Did I mention the carb is a mech secondary?
Click to expand...

Sounds like we are on the same track Toyota :salut: Of course, you're a lot farther ahead than I am, but I have hedmans, mechanical secondary/manual choke eddy carb, air-gap, etc. Good luck figuring out the problem, though!
 
Since you've also jetted your carb leaner that can cause it to pop through the exhaust when you let off the throttle from running too lean. The air gap don't atomize fuel as well as a regular intake because it is not heated from exhaust heat so it will require richer jetting than a normal intake. You may need to jet it way richer than you have it now. Believe it or not if you jet it too lean it can actually cause you to get worse fuel mileage because your producing less power so you have to open the throttle farther to get the car to go. Get it jetted correct and it'll get better mileage. Running a cold thermostat such as a 160 degree will help torque but also hurts fuel mileage because it hurts fuel atomization.

Do this.

Make sure your exhaust is fixed and not leaking. Make sure and run at least a 180 degree thermostat. Timing is at 34 degrees total timing in by 2400 rpm. And then play with jetting.
 
thermostat is 180 and carb jets are stock calibration now (100 and 98 with 7047 rods and 5hg springs). I don't have a good timing light so I can only check normal timing which is at 12 degrees
 
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