I need something to do over spring break and i am thinking of putting a cam or manifold in my truck (`75 F-250 4x4, 390). Which one of these would offer the most performance for the least green?

Dave

 

Oddly enough, you really need one to realize the performance gains of the other..

 

to explain better, the compliment each other.. Your not going to really notice one unless you also have the other.. But if I had to choose I'd say intake and carb.

 

Dave you can spend good bucks on a cam, intake & carb. and you may be disappointed in only the slight improvement for the bucks spent. You will put the toe in the carb and burn more gas, and you may not see response much better than before you spent the money.

I hope you make a good choice.

My 2


John

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

do you have headers? headers may give the performance increase you are looking for!

 

Just last week I found a 1973 article on performance parts from Ford for the 390 and 428. They broke down the improvements by $100, $250 and $500 increments and it was a hoot to see those list prices. Now you probably want me to find it again; I know that the order of improvements was not what I expected. On the other hand, I personally am a huge fan of rv camshafts -- especially for trucks. Putting on big carbs and fancy intakes are easy projects but usually not worth it; even more true with today's $1.52 gallon gas prices.

Lee
1965 F100 short box styleside

 

If you go to the trouble of changing the cam, why not change the manifold too since it is already off? Conversely, if you change the manifold, you already have the pushrods and rocker shafts off so why not go a little further and change the cam too? Big manifolds don’t like small cams and vise versa. I agree with jowilker though, it’s a lot of time and money for the increase. A great carb. for a stock 2 bbl. 390 is the Holley 500 cfm 2 bbl. Change the main jets to 71’s and bolt it on along with a good dual exhaust system from the stock log manifolds. This would give you the greatest bang for your buck.

 

Frank, I disagree, engines operating under 4000 rpms will get along just fine without headers. Dual exhaust yes. :-)


John

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

$1.52! what a bargain the cheapest gas around here is 1.65. anyway, headers are not an option as all I can find are the ones that hang way to low, I would bust em of in a week. I dont have the stock cam, but i dont know what it is because my dad lost all the records from the shop that build the engine and he cant remember. I have a 4bbl intake as this engine is a car version, with a 600 carter carb. does this make a difference?

Dave

 

dave, I think you need to enjoy what you have. Spend your $ on the outside, wheels, trim, tunes, etc.


John

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

4BBL Carbs and manifolds do not seem to help much on the FE engines, but a set of headers and a good cam do make a difference. I base my opinion on the outcome of racing my dad up a hill. His truck is a '70 F250. Very similar to my '69 F250 that whooped his azz. Both trucks had .030 over 390's; 2¼ dual exhaust & glasspacks; C6's; 3.73 gears; identical size tires; and both Camper Specials. The only advantage I had was a 268 Comp Cams and headders. He had a 252 Comp cams and stock exhaust manifolds.

Every other advantage was his. Both of my gas tanks were full, one of his was empty. I had a 250 lb canopy and my 200 lb brother with me, dad was alone and unloaded. I had a stock Autolite 2BBL, he had a 4BBL manifold (car style) and 625 CFM Carter AFB.

He was seeing my tailgate by the time I reached 45MPH from a dead stop on the hill.

I have tried two different 4BBL carbs on top of an Edelbrock manifold and neither one really gave much more oomph below 3000 RPM than the 2BBL, just worse mileage. Possibly with a set of aftermarket heads, a 4BBL might be more worthwhile; but at over $1200 for a set of Edelbrock aluminum heads,we are talking some serious money.

 

I am not sure exactly what kind of performance improvements you are looking for but making a big difference over your 4 bbl intake is unlikely. I still like the idea of a new camshaft especially since you don't know what you have. And I agree with the other posts about exhaust; duals. They are important but other wise you really have to start at the engine and redo the entire system all the way out to make a difference. How about something radical? If you are looking for more bottom end torque and better mileage, how about going with a 500 cfm carb? Stock 2 bbls on 390 were only 475 cfm units so it is viable.


Lee
1965 F100 short box styleside

 

well, I have a 600 carter carb, like I said before I dont want headers unless someone knows of some that wont hang below the frame. I have dual 2 1/4" exhaust, so I guess that the basic idea is the cam would help me the most right? I did find out that I have some sort of RV cam, thats all that the sheet from the rebuilders says. would it cost an outragous amout to have some headers custom built?

Dave

 

Dave, seems like maybe you need to take it Charlotte and get Robert Yates to tune for you.;-)


John

66 F100s
In the still cool hours of the night, you can hear chevys rusting away.

 

Jowilker, maybe Im dumb or something cause I dont know what that means.