Trying to increase my mpg
Thread Starter
|
New User
Joined: Apr 2017
Posts: 8
Likes: 0
Trying to increase my mpg
I have a 1986 f250 with a carbed 302 and either a c5 or c6 automatic trans. I canged it to a holley 650 4bbl and ended up getting loke 8mpg i switched it back to 2bbl now it wont pull well. Any suggestions?
Moderator
Joined: Jan 2001
Posts: 56,948
Likes: 2,717
From: Virginia
A smaller holley 4 barrel or edelbrock would probably work better and give you your fuel mileage back. I know most 650's are double pumpers. Is that what you put on there? You need a street carb around 600 cfm or so.
After that you need to get rid of that c6. Get some sort of overdrive trans in it, and that will help it. Do you know what your gearing is? You can look at a tag on the rearend or look at the code number on the doorjamb tag. It may be 4.10's in it since it's a 302. What size tires are you running? Does it have a lift on it?
After that you need to get rid of that c6. Get some sort of overdrive trans in it, and that will help it. Do you know what your gearing is? You can look at a tag on the rearend or look at the code number on the doorjamb tag. It may be 4.10's in it since it's a 302. What size tires are you running? Does it have a lift on it?
Junior User
Joined: Oct 2016
Posts: 50
Likes: 0
From: On the bayou
A 650 cfm carb is too big for a stock 302. Even a 600 cfm is too big for a stock 302. Although you can always go down a few sizes on the jet which will help some. A 500 cfm 4 bbl is a good size. I think quickfuel makes a smaller carb. I think it's a 470 or 490. Not sure how it will work with your motor but it's only around $300 new. Holleys have big primary venturis that kill mpg but are good for performance. I'm running #63 primary jets in my 85 bullnose and it's still a bit rich but runs well through all circuits. I get anywhere from 15-18 mpg on the highway. You can also change your accelerator pump squirter to a smaller size. My old QF 650 that I bought used came with #66 primaries with and #31 squirter. After much trial and error I wound up at #63 & #25 and it helped with mileage a lot. I would try to tinker a bit if you have the time.
Thread Starter
|
New User
Joined: Apr 2017
Posts: 8
Likes: 0
Trending Topics
Thread Starter
|
New User
Joined: Apr 2017
Posts: 8
Likes: 0
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
10 Most Surprising 2026 Ford Truck Features!
Joe Kucinski
Top 10 Ford Trucks Coming to Mecum Indy 2026
Brett Foote
5 Best / 5 Worst Ford Truck Wheels of All Time
Joe Kucinski
Ford Super Duty: 5 Things Owners LOVE, 5 Things They LOATHE!
Joe Kucinski
Every 2026 Ford Truck Engine RANKED from WORST to FIRST!
Michael S. Palmer
The Best F-150 Deal of Every Trim Level (XL through Raptor)
Joe Kucinski
Moderator
Joined: Jan 2001
Posts: 56,948
Likes: 2,717
From: Virginia
I thought so. That is a race carb. I bet it didn't run that great with it either did it? Big bog when you nailed it correct?
I don't recognize anything on the tag except it may have 3.55's in it. They usually punch a hole right through the 3 for the mounting bolt. 3.55's would not be a bad gear for that truck with that small engine.
This engine was originally fuel injected correct? Was the whole engine swapped or was it converted to carb? What fuel pump system does it have? It's rare if all this conversion was done neatly and correct.
I don't recognize anything on the tag except it may have 3.55's in it. They usually punch a hole right through the 3 for the mounting bolt. 3.55's would not be a bad gear for that truck with that small engine.
This engine was originally fuel injected correct? Was the whole engine swapped or was it converted to carb? What fuel pump system does it have? It's rare if all this conversion was done neatly and correct.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Yep, 3.55's like Dave said. But, a 600 CFM carb is about right for a 351, so I'd go smaller on the carb for a little 302. (A 302 in an F250?)
And, I agree with Dave on ditching the C6. It is a power hog, and it kills MPG.
Show us a pic of the distributor, as that'll help us understand what ignition system you have.
And, I agree with Dave on ditching the C6. It is a power hog, and it kills MPG.
Show us a pic of the distributor, as that'll help us understand what ignition system you have.
FTE Legend
Joined: Jul 2010
Posts: 32,875
Likes: 48
From: Northeast, OK
Yep, they all had a distributor and a coil. But what we need to see is if there's a vacuum advance on the distributor. That will tell us if the ignition advance is computer controlled or not.