new 94 carburetor gas mileage

[wolfie]

I installed a new 94 Dennis Carpenter carburetor recently and have been very pleased with how it runs. This is a great carburetor. However, the gas mileage has been disappointing. I have a stock 1940 four door. My driving is just around town with no long trips. With my old carb I would get in the 10-13 range. I've filled up twice with this carb installed and I've gotten 8.5 and 9.6. The accelerating pump connecting link was in the number two hole and I've just moved it to the number one hole to see if that makes a difference. I was expecting a little better MPG with this carb. Any ideas on what I could look into to improve my MPG?

[Ol' Ron]

AF meter!!

[Old Henry]

Reduce the size of the jets. I got three more highway mpg by going from 51's to 47's.

[wolfie]

You old guys have good ideas except I don't know what an AF meter is. Would you explain that Ol' Ron?

[ken ct]

Originally Posted by wolfie

You old guys have good ideas except I don't know what an AF meter is. Would you explain that Ol' Ron?

Sounds like your not into old cars much if you dont know what an AF meter is. Once you start messing with that new carb DC may not honor the garentee,i would send it back as defective.Personally i would rather have an original rebuilt by a competent rebuilder. There are a few of them that post on here Charlie,ny,52 Henry,will do a fine job on it. OMO ken ct.

[Kurt in NJ]

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It is a gauge that uses a senser in the exhaust like your modern car --only instead of directly changing the fuel mixture it can be read on a gauge or computer ---it is a way of telling how rich, or lean your engine is running

Another important factor in economy is the vacuum brake in the dist---back the adjusting screw all the way out, then only adjust it in enough to stop the ping---most times it won't need to be screwed in very far if the dist is working and setup properly

[V8COOPMAN]

Originally Posted by wolfie

You old guys have good ideas except I don't know what an AF meter is. Would you explain that Ol' Ron?

"AF" meter is a device that measures "Air/Fuel" ratio. DD

[Charlie ny]

Wolfe,
I've heard this before....good running carb not so good mpg. The ones I've
worked on had at least a 7.5 power valve which brings the power circuit in too soon.
The jets were also a bit big. A 5.5 PV and 49 or 50 jets ( at sea level ) seem to
make things happier in the mpg area.
As Ken rightly cautioned once you take it apart the good relations between
you and Carpenter are real shakey.........this is understandable, a big outfit like
Carpenter can't accommodate certain situations as easily as little guys.
Charlie ny

[Newc]

Hi; Just a note. Long ago the Forum had a discussion on the carb float bowl vent location for crank fan engines, 39 dlx and all 40's. This may apply to the above problem? Newc

[19Fordy]

Is it true that if the jets are too small, you could burn your valves? I am thinking about what Old Henry said in his post.

[Ross F-1]

Old Henry is at very high altitudes. Personally, I think #47's are risky. Valves cost more than gas, but he doesn't have problems so far.

[Old Henry]

Definitely want to check the spark plugs not long after reducing jet size to make sure you're not too lean for your altitude. Plug should be light tan. If too light - like white - too lean. If just dark and not tan - too rich. If black carbon deposits on them - way too rich. But I ran 51's over 12,000 feet going over Rocky Mountain National Park a year ago and my plugs were never black carbon - just dark. I had put the larger jets in a few years ago to reduce my engine temperature which it did but lowered my gas mileage. Switched them back and got 3 more highway mpg and plugs are now light tan, almost on the white side, but OK. So, it's a trade off - a delicate balance - richer is cooler but less efficient. Leaner is more efficient (better gas mileage) but hotter.

[flatjack9]

Originally Posted by 19Fordy

Is it true that if the jets are too small, you could burn your valves? I am thinking about what Old Henry said in his post.

A lean mixture will burn slower than a proper mixture. Therefore you get a lot of heat going out the exhaust, hence the possibility of burning a valve, especially at higher load conditions.

[Bassman/NZ]

Originally Posted by Old Henry

Definitely want to check the spark plugs not long after reducing jet size to make sure you're not too lean for your altitude. Plug should be light tan. If too light - like white - too lean. If just dark and not tan - too rich. If black carbon deposits on them - way too lean. But I ran 51's over 12,000 feet going over Rocky Mountain National Park a year ago and my plugs were never black carbon - just dark. I had put the larger jets in a few years ago to reduce my engine temperature which it did but lowered my gas mileage. Switched them back and got 3 more highway mpg and plugs are now light tan, almost on the white side, but OK. So, it's a trade off - a delicate balance - richer is cooler but less efficient. Leaner is more efficient (better gas mileage) but hotter.

I think you mean if black carbon deposits on them - way too rich.

[Old Henry]

Originally Posted by Bassman/NZ

I think you mean if black carbon deposits on them - way too rich.

Right you are. I knew the right answer just couldn't get it through my fingers right. I fixed it. Thanks for the correction.

[wolfie]

I definitely don't want to take anything apart on this carb without talking to Carpenter. I will do that first. Thanks for all the comments.

[joe plumber]

Originally Posted by wolfie

I installed a new 94 Dennis Carpenter carburetor recently and have been very pleased with how it runs. This is a great carburetor. However, the gas mileage has been disappointing. I have a stock 1940 four door. My driving is just around town with no long trips. With my old carb I would get in the 10-13 range. I've filled up twice with this carb installed and I've gotten 8.5 and 9.6. The accelerating pump connecting link was in the number two hole and I've just moved it to the number one hole to see if that makes a difference. I was expecting a little better MPG with this carb. Any ideas on what I could look into to improve my MPG?

Wolfie it's strange you didn't catch hell cause you brought the wrong carburetor .If it ain't a new English made 97 it can't be any good .JMO.That's the general consensus I come to gather from certain ones on this site .

[ken ct]

Originally Posted by joe plumber

Wolfie it's strange you didn't catch hell cause you brought the wrong carburetor .If it ain't a new English made 97 it can't be any good .JMO.That's the general consensus I come to gather from certain ones on this site .

Engilsh or otherwise 97's are not correct for a 39 in the first place. 1939 ford used a 91-99 [94] made by Chandler-Groves. Any carb that is a Ford script either F or H is not correct either. Ken Ct.

[joe plumber]

Originally Posted by wolfie

I installed a new 94 Dennis Carpenter carburetor recently and have been very pleased with how it runs. This is a great carburetor. However, the gas mileage has been disappointing. I have a stock 1940 four door. My driving is just around town with no long trips. With my old carb I would get in the 10-13 range. I've filled up twice with this carb installed and I've gotten 8.5 and 9.6. The accelerating pump connecting link was in the number two hole and I've just moved it to the number one hole to see if that makes a difference. I was expecting a little better MPG with this carb. Any ideas on what I could look into to improve my MPG?

Hey Ken , I know they aren't stock for a 39.Not stock for a 40 either which is what he has He doesn't have a 39.
"Sounds like you are not into old cars "

[ken ct]

Originally Posted by joe plumber

Hey Ken , I know they aren't stock for a 39.Not stock for a 40 either which is what he has He doesn't have a 39.
"Sounds like you are not into old cars "

Oops i thought he had a 39 ok my mistake a 91-99 ford or holley would be correct. ken ct.