I have a 1974 F-100 300-6 and 3 on the tree. I want to pull a loaded 21ft camper at 70mph uphill !!! Does anyone have any ideas how to get more power from this stock combo ? I would like to go to a 4spd. Maybe a 2bbl ? Header ? Balanced engine and new 9:1 pistons ? port n polished head ? Any help would be appreciated !!

 

Not in your wildest dreams. MAYBE if you dropped a built 460 into it.........

 

....With Nitrous..! lol

 

The only way to get more power from an I6 reliably is with a stock EFI engine. But even with that, it'll have to be a gentle hill for you to hold 70 with a big trailer. A Kansas hill; not a Virginia or Utah hill.

 

You could lower your rear axle ratio, but! Caution do not over load your breaks, pulling a load is nice but stopping one is much more important! For a 21 ft travel trailer you really should be using at least a F-250!

 

You do not want more power. Power, by definition is something that increases with RPM. If you build the engine for more power, it is likely to lose performance in the region of 1800-2200 RPM which is what you need for towing. What you need is more low RPM torque.

To that end:

You could be looking at either a very mild "RV" cam or simply using the stock cam with a set of 1.75: rockers from a C***y I6. Put in a set of Cloyes adjustable timing gears and advance the cam 4°.

You could be looking at a mild head re-work. Concentrate on the bowls and valve guides and leave the ports alone, polish, cc and be-burr the chambers and add a 3-angle valve job with back-cut intake valves.

You could upgrade the exhaust manifold to either an HD log manifold with a single 2.5" outlet or to a pair of EFI manifolds which are in essence cast-iron shorty headers.

You could upgrade the intake system to a Clifford or Offy 4V intake with a small 4V carb like a Holley 390 or an Edelbrock 500.

You could rebuild the bottom end of the engine to fresh stock specs. An I6 is inherently balanced as well as it needs to be for use in a truck. If you do all these things, the engine will be appreciably stronger than it is now although it probably won't have much "more power" and will not be appreciably less reliable.

You'll also want to replace the 3-speed with either an NP435 or a T-18 4 speed with a granny 1st

HOWEVER... If you do all these things, you still don't have a chance in hell of pulling that trailer up a hill at speed. Not going to happen, no how, no way. It may go downhill pretty well though.

If you need that sort of performance go buy an F250 or F350 with a Powerstroke.

 

Lowering the RAR will slow the truck down - not speed it up. And lower gears are weaker, so they'd probably break with a heavy trailer long before he got it up the hill.

A stock 4.9L will get you there, but it's not gonna get you & 5 tons there fast.

 

I know my 4.9 would BARELY do 70mph on the flat by its self. Never tried towing with it, then again I only had it about a month.

 

Ellaborate on the "lower gears are weaker" comment. Top speed won't be as high but you most def want lower gears (higher numerical number) when pulling.

 

Then it has problems. Mine spent about a year in a junkyard before I put it into my truck, and it'll do 110 (GPS-confirmed).I don't know how to make it clearer than that. Weaker = not as strong. Removing teeth from the pinion gear makes it MORE likely to break.No, I most definitely don't. I've towed over 10Kip with my 3.08s & ~32" tires. Maybe close to 15Kip for ~100 feet, but the rear yoke (which had apparently been cracked for a while) exploded. It didn't hurt the d'shaft, gears, or axle, though.

 

Efans will help your old engine, im sure youve got a nice heavy steel fan and clutch hanging on the front of your waterpump.

but as its been said, dont tow out of the intended purpose of your vehicle

 

Turbo diesel.

Adrianspeeder

 

A dumb e-fan puts MORE load on the engine than a mech fan. It takes some smart programming in the PCM to make an e-fan more efficient, and these old trucks just don't have it.

 

Thought you might have meant speed wise or something. Sounds like a good way to burn up the transmission.

 

You lost me - what's a good way to burn up a transmission???