Hi, I currently have a 351W in my 66 F100. Trying to decide whether to rebuild the 351 to increase HP or to replace with a 390. Which would be the bigger bang for the buck to increase HP?
thanks!

 

There are plenty of things to be done to the 390 and it's a cool mill (imo) but the 351w is cheaper, and not just because you already have it.

 

IMHO, unless you have a desire to go back to a FE engine because that's what came with the truck I'd stick with the 351W.

 

Not sure how much of a difference MPG between 302 and the 351w but I have the 65 with the 390 and the other with the 302 and visiting family some 300 miles the 65 with the 302 makes the trip on a tank of gas; on the otherhand, the 65 truck with the 390, which I affectionately refer to as my gas hog' I stop checking MPG after the 2nd tank of gas. Out of both 65 F100's I prefer the truck with the 302; I can haul just as much weight as the 65 with the 390.

 

Sorry for the hijack but what you are saying is the Flareide gets better MPG . For my own reference what rearend ratios are you comparing in these trucks?

 

If bigger is better why not go 460 . Lot of f350 box vans have them and they go for cheap.

 

I looked at your album. It looks like some one did a pretty good job installing the engine. I would stick with the Windsor, it's all there and working, all you have to do is take it out freshen it up tweak it a little and stick it back in. If you go with a 390 or a 460 you will have to change a lot of parts and pieces to make them work. Plus either the 390 or 460 will add a lot of weight to the truck and it takes fuel to move weight. Remember for every pound you loose it is like getting free horse power. A 100 pound weight reduction will reduce a 1/4 mile time by 1/10 of a second.

 

I put the engine in years ago. I didn't really know what I was doing back then. I originally had the fan on the engine until the fan blades hit the radiator. I put an electric pusher fan on and haven't had problems since. The truck has a lot of sentimentAL value since I bought it from my dad. My dad recently gave me his 94 f150 since he never drove it.

 

Recommendation for component combinations for the 351W. I like the Sniper fuel injection from Holly.
I have never build an engine and don't know how to figure bore, valve specs or what crank and pistons to use. I would like the 351W to be a weekend driver and be able to move when I put my foot in it.

 

That is a 64$ question. You will probably get a lot of input on that before it's over.
If you have never built an engine it isn't all that complicated. I would suggest you buy a Ford shop manual that has the 351 Windsor in it. I like the ones that were printed between 70 and 74 they seem to have more information in them probably because the mechanics in those days were expected to actually repair something instead of replace it. Find a good automotive machine shop that you can trust and consult with them before you buy a lot of parts. All you can do yourself is assemble it. You are depending on the machine shop to get everything to the correct dimensions. Also you can start a new thread over in the Windsor forum.
I would pick a realistic target number for Horsepower and torque. Most any Ford engine can produce and handle 1 horse power per cubic inch and be reliable with stock parts. When you try to go past that your cost can skyrocket in a hurry.
One last thing, your static compression ie. 10-1 will determine what cam you can use. Any cam manufacturer will steer you in the right direction if you can give them a good solid number for your static compression. Because what the engine sees when it's running and what determines if it will run on 91 oct. fuel is the dynamic compression and that is determined by the cam. In other words the dynamic compression needs to be around 8-1 or less to burn pump gas.

 

I posted a picture of the specs when I had my 351W overhauled. I'm assuming it was bored .030 over.

Original overhaul paperwork 351W

 

There was a column in HRM a while back titled "Because Torque". The guy talked about the big inch motors he had with small carbs, mild cams--I can' recall the details.

Anyway, do a freshen up on the 351W and put a stroker crank in it. Carefully select pistons for 9 to 9.5ish compression. If your heads are sound, stick with them. Your RV cam is probably a winner too. Smallish carb or the EFI route as per the post above.

Now you can pull an OD transmission or even a taller gear. Some OD transmissions have really tall OD so you can run a shorter gear, making it run a little easier at slow speeds. But with low end torque, you don't really need low gears, just a good clutch or an automatic.

With a motor like that, if you don't like the 800 to 4500 rpm power band, re-cam it, put on a single plane manifold and toilet sized carb or bigger efi, valve springs and run it to 7500 rpm and see what you think.


Serving suggestion. ymmv.

 

Don't know how many miles since the overhaul but it appears they used the basic rebuilder parts. From that number on your receipt those are Enginetech pistons. I would say with those pistons you will be lucky to have 8-1 compression and maybe less than that. If it were me I would put new pistons on the top of the list and try to get the compression up too at least 9.5-1, change the cam, along with the EFI and some headers and you will be amazed at how much better it will run.
On a side note about Ford and their advertised compression, they lied a lot, especially in the late 60's and early 70's. If you take one apart and measure everything and do the math they rarely live up to what Ford said they were.

 

Great information. Today I'm going to see if I can find casting numbers on the block. I found a,Web site that explains how to tell what heads without removing them.

Thanks agian

 

Everything I've read or heard about 302 and 351w heads is that they're not great in terms of flow. If you still want to remain more or less stock but want to gain a few HP you might consider some GT40 heads. There are considerations you have to take into account regarding header selection but they are iron Ford heads and should improve your overall performance without breaking the bank like a nice set of aluminum heads would. The holes would need to be enlarged for the studs or head bolts on your 351w and if you're going to install a different cam then valve springs as well.