1975 F100 4.9 build. Carburetor opinions
 

Hello all. Figured i'd tell you about my engine plans and truck and see if anyone has any pointers or opinions on what could be better since you all are the 300 experts.

Background: I somewhat collect/buy/sell the 73-79 trucks. I've had/have quiteeee a bit of them. Plan for this one is to "build" it into something that I would want to jump in and drive to work on most sunny days. Make it Fuel efficient as possible and lightweight as possible (without getting silly). And I know these are not meant to be fuel efficient, i'm looking at it as more of a fun challenge.

I was able to find exactly what i was looking for, a completely base 75 F100 Short bed, 300, Auto(c4), non-ac, PS, Manual Brakes. Did not want the big bulky AC unit in the engine bay, no extra weight, the truck didn't even come with a radio. (I'll put one in tho) But you look under the dash and it is so clean, all factory wiring, no high schooler modifications.
Truck came out of Alabama and is completely rust free, has its share of dents and dings. I'm in Ohio.

So far in the weight reduction area I have removed right around 170 pounds. Consisting of, Large steel bumper, spare tire and rack, emissions canister etc., other odds and ends under the hood that were not needed. I will be adding a rear roll pan so will need to add that in. Will also be adding and subtracting weights as things get changed. Will be adding aluminum rims. And will find a scale and find out what the whole truck weighs.

As for the engine I am going with the dual efi manifolds and Walker 45166 down pipe. Putting on an Offenhauser intake. I bought a dual port off of summit but am considering returning it for a C intake. Aluminum Radiator and Electric Fans.

Now My Question: for My Carburetor setup, I was planning on going with a new EFI setup, Fiteck or Holley Sniper. After talking with a guy that owns a bronco/truck shop he had great things to say about the Sniper. But, after looking into the main sniper kit more they say you need 250-650hp. So another option is their new "2-barrel 2300" efi sniper. (580 cfm) I think it would be cool to have the system on the truck. If i go with the 2 barrel I would need the C Offenhauser with an adapter plate. The whole kit is $1000.

https://www.holley.com/products/fuel...parts/550-849K

Could go with a Holley 390, which I see a lot of people are doing but that will run you $450?

Edelbrock 500cfm? I have an Edelbrock 600cfm 1406 sitting on the shelf in the shop.

I think I've only seen one 300 with a Fitech installed but it was heavly modified. I believe my engine is pretty stock, Runs Great. Also found a receipt for the engine rebuild in 1997 but it did not get descriptive.

Thanks, i'll get some pictures up.

My son and I have been looking for a 2wd, short box, 300, a/t, p/s, p/b vehicle for the grand kids to drive through high school and college. We have seen a lot of them in various stages of rough but few have the package we desire.
I don't have experience with aftermarket EFIs so I would probably choose a 1.08 Autolite 2V. They seem to be easy to wring out initially.
Your Edelbrock would probably work too, but its more than you will need.

Are you going for a power increase or strictly a MPG increase deal?

If you want simple then I'm with FTF on this the Autolite 2100 2V 1.08 carb is simple and reliable and cheap. I can buy one of these carbs, rebuild it and be ready to run it for less then $100. I like to add bushings and O-rings on the throttle shafts when I rebuild mine. These carbs are from the late 50's-the 60's. The O-rings are overkill but help eliminate any chance of a vacuum leak at the throttle shafts.

I would stay away from the Holley 390cfm 4V. They can be a little bit of a pain to get them to run right on the 300.

If you want the 4V then either a Edelbrock 500 cfm or a Summit Racing 500cfm carb ( SUM-M08500VS ) would be the way to go. But the 4V isn't needed.

The EFI will be more expensive, more complex and have more things that can fail. When they work, they are great. When there is a problem they can be a pain. I like the carb because when there is a problem you can usually fix it with a screw driver. With the EFI when there is a problem you need a glove box full of spare parts and a lap top ( depending on the system ) .

But it really depends on what you want out of it.

https://cimg5.ibsrv.net/gimg/www.for...31486ac93.jpegHave a front fender to replace the dented one.
https://cimg6.ibsrv.net/gimg/www.for...b23d860e3.jpegTailgate was dented. Luckily I also had one sitting in the barn.
https://cimg7.ibsrv.net/gimg/www.for...3c24660eb.jpeg
https://cimg9.ibsrv.net/gimg/www.for...8e28b2de6.jpeg

You could upgrade the rocker arms, advance the cam timing 4 degrees with a set of Cloyes timing gears and then put on your Edelbrock 1406 to try before going to fuel injection.

Yep they will accomplish both. Make sure to go with the C-series ( especially if you go EFI ) .

There's no reason the EFI won't work. And with some easy driving you should be able to get high teens to lows 20's on the MPG. A manual transmission would help that too.

Nice looking truck. You've got a cool project there.

I am a little confused by your thoughts.
I agree that it is possible to spend enough money that you will never see a positive return on your dollar investment, to say nothing of the time involved.
If you just want to try something as an acedemic exercise without regard to saving money in the long run then just install a factory EFI system. Available cheap - I have a complete take-off if interested. But even that will entail fuel pump(s), return lines, etc. modifications to your truck's fuel system. But the mileage will be hard to beat with anything else.
Now if you want "cheap" then do a 2V conversion.

And don't neglect a more efficient exhaust system too. That is where you will see a real bang-for-the-buck.

[EDIT: I now see EFI exhausts in the box - good choice. Nice truck btw - I'd love to find one appropriately equipped for a teen aged girl.]

To be honest I don't know much about the factory EFI system. I'll have to do some more research on it. I guess what I am trying to decide between is, would the Sniper make a worthy noticeable difference (mpg, performance, convenience) over a carburetor setup. If so I don't mind spending the money. Not necessarily looking for cheap but don't want to throw money away.

And as for exhaust, Already have the EFI separate manifolds, can see them in the bed.

TL;DR: If you do the EFI install, you need to drive about 7,000 miles to make back your cost on the Sniper EFI system, assuming you see a 2mpg increase.

I add up numbers in my day job. So here's some number-crunching:

- Sniper EFI cost = $850
- Autolite 2100 = $100 (junkyard carb + rebuild kit)

So you're working with a cost recovery of $750 in total if you go the EFI route. You need to know at what point you are ahead in fuel costs saved vs. the actual install cost.

Now everything else being equal, and assuming you drive 5,000km/year (3,100 miles or so) with the truck, let's assume that the Sniper setup gets you an extra 2mpg vs the carb. And, let's assume that the average price of gas is $3.56/gallon. With those numbers, you get a cost savings using the EFI system of $349.21/yr. This means it will take you at least 6,200 miles (or just over 2 years) to "save" money on the EFI setup.

And this just takes into account the dollar cost. There's also the time involved in doing the conversion, and all the other little things that come with doing electronics work. So you will likely have to drive another 1,000 miles or so to break even.

I had to do a smiliar calculation for my own truck when I was deciding between keeping the propane conversion motor it came with (and the headaches that come with running a propane truck) vs switching back to gas.

Thanks for running the numbers! I think i'll do something different and try the holley 2 barrel sniper. If i don't i'll keep thinking about it over and over. If it doesn't work like i want i can always sell the system or try it on something else I have.

You know when I was coming up everybody thought more was better, more carb, more cam, bigger exhaust, bigger valves, bigger ports, etc. But that is not always the case, start off with small increments of change to start and then move up from there.

The 300 is a different animal then the V8's. The 300 likes the big cam, big ports, big valves and bigger exhaust ( to a point ) . The cylinders are so big and the head is so restrictive that anything you can do to increase air flow helps them.

I picked up my 81 F100 flare side with 300 six and T18 with the hope it would do better than my 02 Durango DD that gets a high of 15 mpg.
I also went with the EFI exh manifolds in to the stock exh system out behind the rear tire.
I kept the stock 1v carb and will see how that does for now. And no I have the stock air filter on it now.
http://cars.grantskingdom.com/var/re...201_174106.jpg
If I come across a intake I would go with a Holley 2300 2v 350 cfm carb with adaptor as I like Holley's and have a "pit box" full of gaskets & jets, etc.


When it gets on the road, cab off frame rebuild right now, I would like to go with a Gear Venders over drive unit but we will see as I have long way before truck sees the road.
Dave ----

I'll bet you gat close to 20 mpg.