8BA Flathead Fuel Mileage Excessive?-Carb

markdtn

markdtn

Senior Member
So I took my tractor (9N tractor with bone stock, just rebuilt, 8BA from a '50 F1 truck)to the exhaust shop that is 1/2 mile from my house yesterday. It used almost a quart of fuel to get there. It used over a quart to get back home this morning, but it is uphill and I was going a bit faster. My "fuel tank" at this instant is a gallon washer fluid bottle so I can see the level well. It has a stock Airtex mechanical fuel pump. It has a built-by-me Holley 94 carb. I have checked the power valve and it seems like it is holding. It will only run with the choke out just a little. I cannot find any vacuum leaks using a propane torch. Timing is set correctly I think. (disconnect advance and line up the pin on timing cover and dot on pulley). Idle screws are out about 1 1/4 to 1 1/2 turns. It is rich smelling. Plugs don't look too bad but it only has maybe an hour total running. Not sure what to do next. Replace power valve anyway? Replace the whole carb with a new one? I am a bit rusty on carbs, been dealing with later FI stuff for a while now.
 
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Not something as basic as that the engine is leaning more then it was from origin and that is affecting fuel level in carburetor ??
If the main jets and powervalve is correct try adjusting the float level a bit.
 
Why is you're choke out when driving it ? Also, was the engine sitting running before you drove it ? The million to one gear ratio I'm sure had something to do with it too.

Sal
 
flatheadmurre said:
Not something as basic as that the engine is leaning more then it was from origin and that is affecting fuel level in carburetor ??
If the main jets and powervalve is correct try adjusting the float level a bit.
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Same angle really, relatively flat. I will try and adjust the float level.

scicala said:
Why is you're choke out when driving it ? Also, was the engine sitting running before you drove it ? The million to one gear ratio I'm sure had something to do with it too.

Sal
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It won't stay running if you put the choke in, it dies. This is a fresh rebuild, it has about an hour running on it. With the 4 cyl it will run all day on 8 gallons. I realize that the V8 will use more, but I was thinking it would be better than 2 mpg. This is a bone stock rebuild. Stock cam, stock heads, stock exhaust, stock intake, single stock carb, etc. It weighed 2200 lbs with the 4cyl, so lets say 2400lbs with the V8 to be very generous. No water in my tires.

flatford8 said:
Check your oil..... make sure it's not going there..... Mark
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I will check, hopefully not.....
 
If you have to pull the choke to run, you may have some blockage in the carb passages or you have an undetected manifold leak. Pulling the choke is enriching the already lean mixture so something is going on there. Having the right spark adjustment can make a difference in mileage too. You will have to get it running correctly to see how it's going to do on fuel consumption. Also keep in mind that a V8 is twice the engine of the of the old 4-banger. Miles to the gallon doesn't equate as well when you are only going 15 or 20 miles an hour in road gear. Now you are figuring gallons per hour.
 
I don't think the load a matic distributor is working right.. Start the engine, bring up the idle. Now advance the dist and tak it for a ride. One way to check the carb is to put your hand ofer the carb slowly and listen for the engine to speed up some or die. This tells you your fuel ratio rich or lean. Some old time tuning tricks.
 
You could have blocked passage on one barrel of the carb, starving 4 cylinders. When you pull the choke to feed those 4, the other 4 are drowning in fuel.
 
I'm afraid it is the fuel pump putting fuel in the oil. That is part A of the issue. I don't really need a fuel pump, it will be able to gravity feed. If I were to take it off, I need to block the hole where the rod was to avoid an oil leak? Can that be done with a welsh plug with the intake on? Brand new Airtex pump (not NOS or anything), that just bites.

So part B is the running issue. I think the distributor is close. Not only is it where the timing says it should be, but it seems to run best there. I just have to figure out why it wants the choke on. I am tempted to remove the power valve and run bigger jets. This is a tractor, it won't accelerate and decelerate like a car/truck does.

But first, I have to change the oil before I do anything else. Hope I have not damaged bearings.
 
Just leave the push-rod and pump installed but dis-connected from fuel supply at least until you get the whole thing running as it should.
 
Find a bolt that fits in the bore of the push rod well and trim it to stay stationary. If the rod is an odd size a bolt can be lathed to fit. Just drop it in and gravity will hold it. On the distributor, try to rig a mighty vac type hand operated vacuum pump to pull vacuum on the distributor can. Pull up a low pressure and watch to see the plate moves with the distributor cap off. If it just sucks air, replace with a new can and retest.
 
rotorwrench said:
Find a bolt that fits in the bore of the push rod well and trim it to stay stationary. If the rod is an odd size a bolt can be lathed to fit. Just drop it in and gravity will hold it. On the distributor, try to rig a mighty vac type hand operated vacuum pump to pull vacuum on the distributor can. Pull up a low pressure and watch to see the plate moves with the distributor cap off. If it just sucks air, replace with a new can and retest.
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I'm not wild about the thought of a loose bolt banging around in my fresh engine. I don't see me doing that. It may be fine, but if anything can happen it will happen to me. I may just leave it in place for now and just bypass it.

I have used vacuum and the diaphragm is good. It moves and returns as it should.

Mike51Merc said:
Thanks for the morning laugh. I was thinking of the gearing, but you nailed it.
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The gears are 6 somethings, but with 28" tires.
 
I found a lawnmower fuel tank for now. It holds about a quart. Disconnected the lines to the fuel pump. Connected the new tank to the carburetor to run as gravity feed. I left the filter inline for now.

Drained the oil with it cold. I wanted to flush it to get as much gasoline out as I could. I had changed oil in my DD last week so I poured that in. Cranked it up and let it run about 5 minutes. Drained that out and filled with fresh oil. Then I ran it about 10 more minutes. It's holding about 50 psi oil pressure at idle. Hopefully I have not damaged it. It seems OK.

I am going to have to get rid of the inline filter, fuel will not go through it much faster than idle. When I get my tank I will use a bowl as original. It seems to idle better. I will next take the top off and verify the float level. I think the fuel pump had too much pressure? I was able to run with no choke now. It has fresh oil and good antifreeze so it is going to have to sit for a few weeks until I can get back to it. I need to spend some time getting parts ready for the Nashville AACA swap meet first of February.

Here is a photo from Saturday. It now has exhaust.

 
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