78 F-250, 4x4, NP435 & 205, 300ci.
I kind of did things backwards in the sense that I have had everything, rebuilt, repaired or replaced, including a fresh paint job, trans, transfer, diffs, susp and now I am thinking about either building up the original 6 or swapping it for a 302 or 351. By swapping the 6 for a v-8, I know I will have to change motor mounts and bellhousings, but beyond that, I don't know what else will be necessary....So the question is, which would be cheaper; to build-up a 6 to get 250+/-hp w/ 315lbs or swap for a rebuilt/modified 302 or 351?

Would a stock lower end w/ a different head (larger valves), cam, header, offy intake and a 500 Edelbrock get me 250+/-hp w/ 315lbs or would I have to do something more drastic?

 

those 300's are torque pigs. if you rebuild, spring for the metal cam gear. check out clifford performance the have a ton of parts for the 300. thier motto is 6=6

 

its alot cheaper to build it up, you can plan on changing exhaust, carburetor, finding motor mount towers for a 302-351w(which are hard to find for your truck), all your belt driven motor accessories, belts, hoses, bigger radiator, plus all the hipo v-8 stuff you will need too (btw; the tranny from a 300 should work with a 302-351w, i dont know about the flywheel though), a good running 300 is a great motor for a truck

 

Thanks for the responses thus far. This is what I kind of figured; build up a six. My rebuilt 6 only has about 53k on it and it runs great. I would just like to keep pace with the newer full size trucks. Not that I'm racing or anything. If the rest of the responses suggest that I stay with the 6, the next question is could I just keep the OEM cam, get a different head with larger valve, new intake etc and get around 250hp w/315lbs?....Clifford has reasonable intake and exhaust, but the heads are salty. Any ideas where to buy heads? Any ideas where I could have an engine built? I live in Indiana.

 

"where to buy heads".......as in aftermarket, i doubt there is a source for that, i would think yours being rebuilt is fine for most anything, the big increase will be in an intake carb combo, a header with free flowing exhaust, a good ignition system (recurving the duraspark will improve it alot) and a cam

 

6=8

 

edelbrock sells better heads

 

They already have a geardrive cam, and you can buy all kinds of stuff for them. I would keep it because it is easier than swapping. The little things will get you, like throttle linkage, clutch z bar mounts, stuff like that. I thought the 6 would be the first thing I changed, but I have been quite pleasantly surprised with it. It will give you decent power, but isn't really a quick, high revver. You should check out the inline forum and fordsix.com. They are both a wealth of info on these engines. As far as the head, the popular one seems to be chevy rockers on a stock head. If nothing else, enjoy its uniqueness. I get a smile when people are shocked that I have a good running, mean sounding six

 

not for a 300

 

I say stay with the 300. That's what I have and plan on rebuilding. The major problem with these engines is that they are anemic. As stated earlier you just need to get it to breathe better. Check out the inline forum and search Col Flashman's 300 six build up. He acheived 300hp and 400 ft.-lbs. Also you can't beat the reliability of a 300.

 

..........

 

I'm fighting this one too... same specs, on a 79 model

300 I6, np435, np205...

I think if I stay gas, I'll soup up the six, athough Jegs has a complete 351w for 2700 that looks pretty mean...

My big thought right now is to try to find a 4 cylinder diesel... I don't know about you, but I had figured better milage out of my six than I'm getting...

 

I would stay w/ the 300... i have only seen one in my life ever have any major problems. those 300's cannot be beat for torque, ***** to the wall... Im headin' in.

 

You have to remember that the 300 is a BIG six. The 1bbl. carb does nothing for performance or gas mileage. It makes a gas pig out of this engine and does so at the cost of performance. The more efficient an engine is, the more power it will produce and do so with less fuel.

So what we really need to do is get the engine to breathe better through a better intake and exhaust. Use a higher power ignition, fine tune the carb, and I would suggest an electric fan.

The only aftermarket head availible is the Allan Johnson. Though it is only for race use, as it does not have any waterjackets. I also heard it runs a about $10K.
There is a guy over at Fordsix, 6banger I believe, that makes heads for the 300. He uses chevy LS1 aluminum heads and sections them and then rewelds. Cost I believe is $2400. That's probably not bad considering no one makes them. I have read some posts where one of these heads would easily make 500+hp possible in the 300 (with other modifications of course...not just head alone).
Your factory head can be made to perform much better than it currently does. Larger valves, port & polish on the exhaust, port on the intake, 1.73 ration rocker arms, ect.