4bbl performance + mileage

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Jul 24, 2004 | 02:20 PM

1984F15016

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4bbl performance + mileage

I am curious how happy you guys running the 4bbl on the 300 are. Is there a noticable difference in power, and how about gas mileage? What about you guys running the 2bbl, how happy are you with the performance, and gas mileage?

Jul 24, 2004 | 04:55 PM

teds74ford

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Good question. Unfortunately, when I bought the truck it already had a holley 390, so I can't tell you before and after. I had it tuned, and it did alright. The guy I bought it from claimed 14mpg. I moved, converted it to 4wd, and have only recently got it running again. I am also about 1100 feet higher than I was before, so it is running a little rich. I estimate that I am getting about 10.5-11 mpg right now, but I am in the process of rebuilding the carb and putting smaller jets in, so I will have to see how it does after that. It leaks, runs rich, has untimed timing, and it still gets that mileage, so I figure that 15-16 is a realistically attainable goal. It is powerful, but not overly efficient right now. I also have a motorcraft 2bbl off a 302 that I have considered tinkering with, but I don't know anything about them. I want to know the benefits of 2 vs. 4 too. Ted

Jul 24, 2004 | 06:37 PM

83Van

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From: Nashville

I lost a good 2mpg switching to the 4bbl [from 14.5 to 12.5 unloaded, or 12.5 to 10.5 loaded way down]. Performance is much better though. Towing a load on flat ground the van would top out at 60-65mph, now it will make it up to 70-75mph with that same load. +10mph and -2mpg seems a fair tradeoff.

Jul 24, 2004 | 09:53 PM

5_labsownus

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From: Fraziers Bottom, WV

Well, I have the Holley 390 CFM on my 300 l6. This week I took my truck on a road trip to pick up 1600 board feet of lumber in a 16 foot trailer. It is figured I hat 2.5 tons on the truck and trailer. I got 12 MPG on the trip and that uas with an empty trailer on the way up and loaded on the way back. I was in the mountains of WV and had to go up Sandstone Mt. That is 5 mile uphill with 7% grade and on the trip their are several steep grades.

The truck top most hills loaded at 55mph, but on Sandstone I went to 3rd grar and 35 mph. But it went!

The last time I calculated the MPG on daily driving I calculated it at 15-16. That is the same as the last dead 1bbl.

Last edited by 5_labsownus; Jul 24, 2004 at 09:56 PM.

Jul 24, 2004 | 10:23 PM

teds74ford

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That's pretty impressive. I noticed you run an electric fan. What other stuff have you done? What did you set your timing at? I hope to get somewhere around there with my mileage.