Hi guys, I am looking for some opinions on which will give me the best mileage, my stock 2V motorcraft carb or going to a 4V. I have heard that because of the smaller primary jets a 4V is more economical as long as you keep your foot out of it, is this true? My second question is, if it would be better to go with a 4V carb what would you suggest for a carb and intake? It would be going on a 351M. And third where can I find the carb adjustments to set the different idle RPM's. I switched from a 4 speed to a C-6 and the adjustments on the valve cover do not apply.
Great web sight and thanks for all the input,
Terry

 

Terry, You will get different opinions on the 2 to 4 barell question. I did a conversion several years ago and was disappointed. I could hardly tell any difference. IMHO you will never recover what you spend in time and money converting the intake and carb in gas savings. As I have said before big Ford iron and gas milage do not compute. You can figure $350-600.00 on a new intake and carb. :-)

John
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In the cool still quite of night you can hear chevies rusting away.

 

If setup properly, a small Holley vac sec will work very well. The secondary is controlled by a spring in the diaphram and can be changed. The 4v carb has smaller primaries that will help with low-end torque and with the proper jetting can get better overall performance.
I bought several carbs at a swap meet for about $50 ea and this allows me to play for cheap, however, if you don't want to take the time to dial in a carb, the old Holley 500~600 vac sec 4V is a good choice and you can get jet kits and spring kits cheap.

As a side note, a properly tuned QJet is an excellent choice too, the very small primaries and overall design can make for very smooth torque down low.

A new alum intake can make a big difference, but it all depends on the design of the original one. As an example, the 390GT S Code intake is almost just as good as the Edelbrock Performer intake, so the $220 is a bit of a waste.

 

keep the motorcraft 2v, put a rebuild kit in it, I wish I had kept mine mileage gains non existent
https://www.ford-trucks.com/dcforum/User_files/3a9df0394b631ce6.gif


77'FORD F150 XLT 400

 

Tnanks to you who replied to the carb question. As for the idle settings I forgot to mention that it is for a 78 F-150 4X4 short bed with a 351M and a C-6.
Thanks again,
Terry

 

I had a 302 that had a supposedly bad motorcraft 2V on. I was talked into putting Edelbrock manifold and Edelbrock 4V 600 cfm carb on it. Yes the carb worked very nicely. The engine went bad later so it came off and is now in service on my 390. Now I have another 302 w/ Motorcraft 2V carb. It has had lean running conditions since I got it that I think I've finally solved after putting new ignition, EGR and rejetting the carb. The carb itself is easy to put jets in. Mine worked well (aside from lean jets). The problem was, that I had to go to a specialty place that charged $125 to put my truck on their sniffer and replace jets to the right size. I couldn't easily find motorcraft jets to experiement w/ myself. Around here in the Seattle area, the specialty shop was the only place that had a selection of motorcraft jets. The 2v now runs better, has proper air/fuel on the sniffer and for now it stays. The thing about putting new 4 barrel on is that you can easily get Holley Jets or Carter/Edelbrock metering rods/jets and other parts. I think that w/ carbs going the way of the dinosaur in general, that those popular aftermarket brands are the only ones that have good parts availibility.

BBT

 

I took off my Holly four barrel and went with the Ford two barrel. The truck starts right up, doesn't leak, runs smoothly, and has good torque. The 390 does not starve for fuel. Also the 2v is easy to rebuild and adjust.

 

Hey fozzy and all,
can you guys recommend good places to pruchase a rebuild kit? I've been wanting to do this, and I've also considered the Q-Jet but haven't the money right now. Would places like Pep / Kragen have them? I did a search on the JC Whitney site that came up empty.
Would appreciate any info u guys would have.

Thanks!

Steve

 

Echobunny, the kits are very readily available at nearly any decent parts house. I really like O'Reilly if you have one nearby. I'm sure NAPA would stock them as well.

 

My mileage went down when I changed from 2V to 4V. The extra power kind of lent itself to driving with extra attitude.

1979 F150 Custom: 75 351W, Edelbrock & Holley
1987 F150 XLT Lariat: 88 351W EFI
Chevy 454: waiting for a truck (Mazda?Nissan?)

 

i had a holley 600 on my 400 and got 12 m/g