new 94 carburetor gas mileage 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?
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Re: new 94 carburetor gas mileage AF meter!!
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Re: new 94 carburetor gas mileage Reduce the size of the jets. I got three more highway mpg by going from 51's to 47's.
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Re: new 94 carburetor gas mileage You old guys have good ideas except I don't know what an AF meter is. Would you explain that Ol' Ron?
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Re: new 94 carburetor gas mileage http://www.zeitronix.com/Products/Products.htm
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 |
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Re: new 94 carburetor gas mileage 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 |
Re: new 94 carburetor gas mileage 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
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Re: new 94 carburetor gas mileage 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.
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Re: new 94 carburetor gas mileage 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.
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Re: new 94 carburetor gas mileage 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.
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Re: new 94 carburetor gas mileage 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.
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"Sounds like you are not into old cars " |
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