Hi Folks,

The truck: 84 f-150 302 v8. Previous owner installed an Edelbrock performer intake and 1406 4bbl carb. While I have the carb tuned properly and the truck runs great I get poor fuel mileage. From the concensus of a lot of other 302/edelbrock carb owners my mileage should be a tad better than 12 mpg. The engine also has 165k and is a little weak. I now have a 3.08 rear axl so my mileage should be better than it was originally was with a 3.55.

Long story short, my neighbor who's a retired mechanic (he retired from being a mechanic like 25 years ago) suggested that maybe my poor mileage is stemming from incorrect carb jetting. As far as I know this carb was taken out of the box and installed. I would put my money on it that the PO never took the time to properly set up the carb.

This being said, what are your thoughts? I think the edelbrocks only have jet adjustments on the secondary side? Or if not, I would at least like to start with the secondaries. How do I even begin to change the jets. Like should I just go with a size down and see what happens? Is there an easier way to determine what size secondary jets I should have? On a side note, I may be using the wrong terminology here... I'm talking about the rods that open and disperse additional fuel when the secondaries are called into action. Maybe they're called metering rods? Anyway, I would like to lessen the amount of fuel when the secondaries open. It's not like the truck gets a boost of power when the secondaries open so this could be a sign I'm just dumping too much fuel.

Any thoughts, input, etc is much appreciated.

Al C

 

If the engine runs well and does not stink like fuel, I do not think you are going to gain much from jetting the carb.

What tranny do you have? What size tires do you run? Is it 4x4? Does it have a lift?

Also, adjusting the timing up may give a couple mpg if you still have it at the stock setting.

 

it stinks like fuel after driving and parking it.

Tranny is a c6, tires are 31" w/ 3.08 rear, it is a 4x4 but front driveshaft is removed. No lift.

I know this sounds like a stupid question but how do I check the timing. I put a timing light on it once before but I can't read the marks on the block and don't know what direction is what and or what the degrees are. I can see the mark on the balancer I just don't know what the timing is set at. I don't have any pinging or knocking and for a 165k engine it runs pretty smooth. There's of course a slight "misfire" or rough idle but only from time to time it's not consistent. I'm hesitant to mess with the timing since it's running pretty good BUT on second thought there are times it's hard to restart after driving. Could be a timing issue.

Thanks

 

When the PO changed the carb. did he also change the distributor to do away with the computer control. If not your timing may be locked down by the computer because of no signal from the carb. I understand that this would definitely affect your mileage

 

Which ignition setup do you have, TFI-IV or Duraspark? If you have TFI-IV (you probably do) then no ignition timing adjustment is possible and you shouldn't attempt it, but with DSII you can adjust it.

Also, if the PO disabled the emissions system on a TFI-IV then you will have very poor gas mileage. A few pics of your engine compartment would be helpful.

 

Usually Ford puts a single pointer somewhere around the front timing cover near the damper, and the damper has a lot of little marks and numbers on it. I usually crawl underneath the front of the truck, and clean the damper off from underneath, turning the engine if I have to so I can see the numbers and the marks. And I will sometimes use white out to mark the factory mark or at least the 10 degree mark so I know where I am at with the light.

If you don't have a pointer, then someone may have left it off.

 

I agree - check the timing. I'm running an out-of-the-box 1406 and getting 14 on the highway at 65 on a 351M 4x4 - but with a 5-speed overdrive manual tranny. But, how you drive and the speeds at which you drive are a VERY important part of the info for us. If you drive 75 MPH then you may be getting all you are going to get. Or, if you drive in town a lot and accelerate hard from a stop then 12 is not so bad.

As for the carb, the metering rods are on the primary side. And any changes you would make would be on the primary side. But, I seriously doubt you need to make changes to the carb. And, if you don't know how to set the timing I really don't think you should tear into it. But, it is possible that the choke is not set correctly and isn't coming off, which will kill the mileage. When the engine is hot the choke should be completely open, standing straight up.

So, take the advice of the others and show us some pictures of the engine compartment and especially the distributor. We can ID what you have and suggest changes.