Advice on Combinations
New User
Joined: May 2002
Posts: 13
Likes: 0
Advice on Combinations
I have a 1986 F150 4X4 4 speed with the 300-6, and a gear ratio of 3.08 if I am reading the code right. Is the YF feedback carb worth rebuilding and pairing with a hi-flow cat exhaust; or should I go with a new intake, Holley 390 and a new hi-flow exhaust system. I'd like to get something over 12 MPG and be able to tow a 3000 lb camper occasionally also. Any thoughts on the rear axle ratio? High enough? Any suggestions about this would be appreciated.Thanks.
New User
Joined: May 2002
Posts: 3
Likes: 0
Advice on Combinations
Hey sammy,
The 3.08 are alright for towing once you get them going, but can be a pain to get there. 3.55's would be better. If you got the money then going with a 4-barrel, cam, and exhaust manifolds would give you a lot more power. But it can be spendy, anywhere from $500-$1200 depending on what you do. THe feedback carbs are ok when they are working, but can go to hell in a handbasket in a hurry.
The 3.08 are alright for towing once you get them going, but can be a pain to get there. 3.55's would be better. If you got the money then going with a 4-barrel, cam, and exhaust manifolds would give you a lot more power. But it can be spendy, anywhere from $500-$1200 depending on what you do. THe feedback carbs are ok when they are working, but can go to hell in a handbasket in a hurry.
Senior User
Joined: Jul 2001
Posts: 470
Likes: 0
Advice on Combinations
Intake, Carb, RV Cam, Exhaust manifold will give you a good amount of power on a stock engine. That would give you incredible lowend but not gain much more horsepower. A 264 cam with a 390 and the EFI manifolds would net you only 183hp (peak torque at below 2000rpm and over 300ft-lbs). A set of headers would get you around 200hp and 310+ ft-bs. You're really limited with the stock compression. At any rate, you'll still have a bunch more power than you had before.
3.08 gears are a little high to haul with, but 3000lb isn't a very large trailor (imo) so I don't think you'll have much of a problem. Is your 4spd 3+od or granny geared? Most of the 3+od i've run into have a pretty high first gear, but (depending on how often you haul) I don't think it'd be worth it buying front and rear gears.
Also, what size are your tires?
-=Whittey=-
3.08 gears are a little high to haul with, but 3000lb isn't a very large trailor (imo) so I don't think you'll have much of a problem. Is your 4spd 3+od or granny geared? Most of the 3+od i've run into have a pretty high first gear, but (depending on how often you haul) I don't think it'd be worth it buying front and rear gears.
Also, what size are your tires?
-=Whittey=-
New User
Joined: May 2002
Posts: 13
Likes: 0
Advice on Combinations
Thanks both of you for the response. Is another cam necessary if I go ahead with a 4bbl, intake and hi-flow exhaust system? What is an RV Cam? The trans is a 4spd with the granny 1st. Sounds like I could get by with the 3.08 but is it difficult/expensive to go to a 3.55?
Senior User
Joined: Jun 2001
Posts: 107
Likes: 0
From: Pater, Maine
Advice on Combinations
The "RV cam" is a cam that is built for more "low end grunt". Basically it probably has more torque off idle to some RPM than say a cam that is setup for street racing which might make the power from 2500rpms - 5500 rpm's. For the I-6 and if you are pulling, hauling or 4wheelin' you want a cam that has great off idle response such as an "RV cam". Might even be able to get away with a cam that operates best between 1500rpm - 5500rpm. Some use the Blue Racer brand, some use Comp Cams. I was going to use a 260h on mine.
Opinion: If I was to put a 4bbl on, I would also do the cam. You want to get the max out of that 4bbl. The stock cam just won't let you do that.
Opinion: If I was to put a 4bbl on, I would also do the cam. You want to get the max out of that 4bbl. The stock cam just won't let you do that.
Senior User
Joined: Jul 2001
Posts: 470
Likes: 0
Advice on Combinations
Even if you keep the stock cam, you will still get a power improvement. An RV cam will just maximize any changes you make.
If you're rockin some 235/75R15's, sticking with 3.08's would be fine. swapping to 3.55's will cost as much as a header + intake + carb will because you need front and rear.
Also, a 390 carb and free flowing exhaust should net you more mpg than stock. The primaries to the carb provide much better atomization, so you get more power for the same amount of fuel. All in all, you can't go wrong swapping to a 4bbl/header combo.
-=Whittey=-
If you're rockin some 235/75R15's, sticking with 3.08's would be fine. swapping to 3.55's will cost as much as a header + intake + carb will because you need front and rear.
Also, a 390 carb and free flowing exhaust should net you more mpg than stock. The primaries to the carb provide much better atomization, so you get more power for the same amount of fuel. All in all, you can't go wrong swapping to a 4bbl/header combo.
-=Whittey=-
