I have a 76' Bronco (Ranger Package) that is all stock. 302 2 barrel motocraft carb, PS, PB, AT (C4) 3.50 gears. Its even has uncut fenders.

Two questions:

1. I am having a recent problem with it cutting off. Sounds like it is starving for gas. A mechanic confirmed that was the problem, but does not know why. It will run fine, starve for gas at random times, even shut down. Will start back up and run fine the rest of the day. We bypassed the manual front/rear tank switch to eliminate that, and it still has the problem. Another guy I know said it sounds like vapor lock? He said put wooden clothes pins on the fuel line just before the carb??

2. Even though it runs good (other than the problem above), I am looking to improve performance in several areas, horsepower, torque and mpg. I currently get about 10 mpg. This seems low to me. I realize this could partly be due to the carb leaking some. I am looking for suggestions. So far I have been told to do something along the following lines.

Change the intake (possibly to an Edelbrock) and go with a four barrel (holly 600 or Edelbrock?) change the cam (suggested crane with 272 duration) and timing gear set.

I also plan on a set of headers. Any suggestions on which I should go with. I read somewhere that due to the Early bronco design, you may be limited on headers because of the way the inner fenders and suspension are placed.

All suggestions are greatly appreciated.

 

That's too much cam for your application, try something a little milder. The carb and intake are right on (as long as you mean a Performer intake) for your application.

 

My 76 F100 w/ 3.50 rear,302,edelbrock performer intake, edelbrock 600 cfm carb was getting around 11mpg
BBT

 

I did a little research at the EdelBrock site and I might go with one of their power packages in hopes that staying with one brand already matched might be easier and better tuned. But 11 mpg listed above... very discouraging.

To the first reply, the Edelbrock cam is listed at 270 Duration, is that much different? Yes, it is the Performer package. Here are the model #'s
Intake 2121
Carb 1406
Cam Kit 2122A
Timing Chains 7814

Is this going to be a good setup?
The last variable I left out of the original post was tires. I am running 30x9.5 BFG AT. But plan on going to a 32x11.5

Hope this extra info helps.

 

I also have a '76 Bronco. It has a 302, 185,000 miles, 3pseed manual, 4.10 gears, 31" tires, and headders. I get an average of 12 MPG. As long as I keep it under 60 MPH on the hiway, I will get up to 15. I only get about 10 when I am towing my 1500-lb snowmobile trailer. Your C4 automatic may be robbing some mileage. I also have no emission control devices hooked up, that probably has a lot to do with mileage. When I first got it, it did not pass the Seattle smog test; so I installed the cheapest catalytic converter I could find and it passed with flying colors.

Get your headders from a Bronco parts dealer such as Tom's Bronco Parts (www.tomsbroncoparts.com) or Wild Horses (www.wildhorses4x4.com) and they should fit no problem. They fit above the starter which has two advantages: Less starter-destroying heat (heat rises) and the starter can be replaced without breaking the headders loose.

From my experience, the stock Autolite and Motorcraft carburetors will get better mileage than any aftermarket 4bbl. The only power increase you will see with a 4bbl would happen past 2500 RPM.

If you want a Crane cam, the 260 would be a better choice for your 8.0:1 compression ratio. Not sure if this cam would help mileage much, but it may. My cam is still stock.

I had similar running problems with my '76 in the past; actually two seperate problems.
1: Anytime it felt like it, it would completely die as if someone turned the key off. All I had to do was quickly "bump" the starter and she would continue on as if nothing happened. I changed the ignition module and it hasn't happened since.
2: After driving for about 10-20 miles it would sometimes gradually loose power and start blubbering until it would not run. I had to let it sit for about 15 minutes before she would start up and run decent again. I also thought it was a fuel problem, so I hooked up a fuel pressure guage to some nylon tubing and tee'd it in to the fuel inlet just before the carburetor. That way I could monitor the pressure while driving. Safe? The pressure did not change before or during the next time the Bronco did the blubbering, so I knew the carb was getting gas. I changed the distributor's cap & rotor and it hasn't happened since.

 

Your cut-out problem sure sounds like a classic ignition module trouble. A fuel delivery problem just doesn't go away like that.
As far as your engine performance goes, here are some thoughts to ponder. Most change the intake and carb first because it is relatively cheap and easy; it ought to be the last thing you do. If you want torque, stick with a 500 cfm or smaller carb. If you really need HP, get a bigger carb but there goes any fuel mileage. A low rpm performer/RV camshaft is the place to start. Headers are okay but don't expect alot of improvement. 302s really need after market (or Ford Motorsport) heads as the stock valve configuration is just too small -- but they are pricey.
But before doing anything at all (except fixing the ignition problem), figure what you have and what you want. You need to know the rear axle ratio and do the math to see what rpm the C4 is sucking up. Get a tach and record MPH vs RPM. Then decide what your target cruising speed is so that everything can be matched to it. You are going to have to pick between your performance desires and want for better mileage. This board will give you as much help as long as you provide the numbers and your choices.







1965 F100 short box styleside

 

It seems to me that your little 302 would be working pretty hard to keep that heavy Bronco moving. Changing to a 4.10 gear would not work the engine as hard and would possibly give you an increase in mileage. The engine will also "feel stronger" with the new gears for the same reason. Just my opinion.

 

To everyone: Thanks for all the input.

I've considered Changing gears to 4.10 after I move to the 32" tires. But in general, doesn't chaning gears to a higher number decrease mileage? Although, I have head it can increase it by keeping your engine in the proper powerband.

What exactly is an RV cam? Who makes one for a 302? Which do you recommend. What kind of duration does it have?

I will get the cut out problem fixed and the tach installed that ole65 suggested and due some monitoring before I proceede. When that is done I will come back to the board with more info. Thanks again.

 

A so-called RV cam essentially 'flattens' out the engine's torque curve. Most stock engine torque curves have a pointed peak , torque rises with rpm to the listed peak torque and then drops off as the rpms continue to increase. The RV cam flattens out the peak so that you have a longer operating range of the engine's highest torque. A good range is 1000 to 2500/3000 rpm. What is very hard to find nowadays are the stock torque curves so you can see what you are starting with. The Edelbrock web site has some examples but you will notice that the engine torque curves are very generic and don't list what year(s) they are representing and yet we know that Ford's 302 came with a number of torque ratings over different rpms. There are a number of cams suitable for your 302 including 'package deals' like Edelbrock's which are both praised and cursed.

1965 F100 short box styleside

 

Why is the edelbrock sometimes cursed? Essentially, what are the pros and cons? It does seem to me that the torque on the Edelbrock is produced at a higher RPM than I would normally be reaching, 3500 - 4500 RPM. I think I would benefit more from a cam with its torque at a lower RPM. Most of my driving is on the road, but I am not looking to do 100 MPH. I want to be able to cruise at 65 with decent mileage, and have more torque at low rpms for trail riding and minor towing. With that in mind, is a low duration better than a high duration.

Thanks

 

For a camshaft, you will want one with a maximum of 220 degrees for a 0.500 inch lift. This will give you good performance as well as mileage, smooth idle and vacuum to run your power brake booster. Running down the highway at 3000 rpms is alot of engine speed; it is best to get that as low as feasible. Remember, your operating rpm should be about 95% of the peak in the torque curve.
As for carbs, it is somewhat akin to arguing about religions. I have always had Motorcrafts, Holleys and one Carter but never a Edelbrock. To me is seems to be an issue of tuning and adjustments. Holleys can be modified and adjusted. Edelbrocks appear to be a run it out of the box situation, no adjustments needed nor possible. It truly is a personal preference and it is really up to you and yours. Just don't get over 500 cfm or the torque and mileage will suffer on your 302.
Lee
1965 F100 short box styleside