thanks StraneRanger that makes good sense so likely if you put a decent set of heads on a 5.8 it would make a serious difference in the peak horse power with the 5.8 loosing its breath at top hp peak and then there would also be the horse power gain that you would get through the rest of the power band with the new heads.
I got a line on a 93 5.8 for FREE!! so I guess my choice should be obivous that I will be building a 5.8 this summer other than the gas millage I think the free 5.8 is the way to go and I can still drive my truck while I build the other motor

 

But if you go too big on the heads, you can end up losing volumetric efficiency at midrange. The GT-40 heads on the Lightning were a big improvement over stock with no loss of midrange whatsoever. The 351 can take still a bit more head than the 40s and still pull like a truck should, but they offer a lot of bang for the buck.

 

Having built and raced both the 5.0 (302) and the 5.8 (351w), the 351w is the better choice of the two for a few reasons. Both are great engines, but when given the choice go with the 351w, it has gobs more torque, is beefier, and as far as the heads are concerned the prices of after market aluminum heads vary around $1,000.00 to $1,200.00, by the time you take your old heads to be rebuilt, depending on how many miles are on them you can easily put close to that amount into them anyway by replacing any valves, guides and any port work you may want to do. If the price of aluminum heads is still out of reach, Ford Motorsports sells a set of complete cast iron GT40 heads for half the price that will work good. The 351w also lends itself to more stroking room than the 302, you can stroke a stock 351w block up to 410c.i. As far as gas milage goes I have a 1982 G.T. that I replaced the 5.0 with a .030 over 351w that has a healthy cam, intake, carb. headers etc... and didn't notice that big of a difference in mpg. but the torque and horsepower was a night and day difference, the 302 that came out was not stock either. My other vehicle is a 1985 F150 with a 302 F.I. and it is a gas hog no matter how I drive it, I actually believe I could get better mileage with a 351w and a carb. 1985 was the first year the F150 was fuel injected and the system sucks. I have been tempted to replace the fuel injection with an intake and a holley carb. and that would probably increase my mileage. Go woth the 351w, you will not be dissapointed.

 

Are these GT 40 Heads aftermarket or are they a ford product, are they like the old chevy 300 horse heads that sometimes you could find on a motor and the person didn't even know they had them?

 

The heads are a Ford item you can find them in the Ford Motorsports cataloge at any Ford dealer. As far as finding them on a production vehicle, certain year 5.0 Explorers had them on them but I am not sure which ones they were plus finding them probably would not be easy. You would have to know what to look for. I don't have my Ford Racing ca. in front of my but these heads are complete and ready to bolt on, they are aimed at the sportsman class racers that require cast iron heads. Last time I checked they were ridiculously cheap.

 

thanks guys!! so these GT 40 heads will work on both 5.0 and 5.8 motors 1993 and 1994. With these heads and rebuilding the motor should I just hone and put new rings on stock pistons or get aftermarket pistons, is there that much difference in a piston brand names and flat tops etc.?I would amagine it would be expensive to bore eight cylinders, it cost enough doing my sleds at 2 cylinders. Another question what is a stroker motor, I have heard of 350 stroker's but dont know what makes it a stroker?

 

Actually the 5.0 Explorers got the GT-40P heads which are slightly different. The biggest change is in the spark plug location which may require that different exhaust manifolds or headers be used. 3-line GT-40s are fairly common at swap meets.

 

The 40s and the 40Ps will work. The regular GT-40s have three lines, the 40Ps have four lines. You can sometimes find the 40Ps on Ebay, right now there are some for $500. You can buy them new for not much more, straight from Ford or a lot of the Mustang type dealers.

Everyone will have a different opinion on internals, but if you watch the major builders then tend to gravitate towards certain brands.

A stroker is when you replace the crankshaft for one with a longer stroke. Common stroker sizes for the 302 are 331 and 347 cubic inches. The 351 can go to 392, 410 or even 427 cubes. Ford Racing even sells stroker kits and engines.


If you manage to get a free 351 the choice is obvious. StrangeRangers comparison of HP vs Torque and peaks is excellent in this case. You can make a 302 make 400+ horsepower, but not with a truck friendly torque curve. The 351 is much easier to build to make both good torque and HP. With the 302 you aren't going to make much over 300 HP/340-350 lb ft of torque unless you move the torque curve up higher in the rev range.

 

Depends on the same of the engine if you bore it or not. believe it or not it is cheaper to bore 8cyls than 1 or 2 because of the set up time for the machine, once it's set up to bore one hole it is set up for the other ones too. As far as pistons go, a good set of Silv-o-lite hypereutctic cast pistons are affordable and offer good strength and service unless of course you decided on any power adders ie: nitrous or forced induction then it will depend on how radical you get with those choices.

 

I called Ford and the told me that they had GT 40x (aluminum) heads for$965.00 a side. That is out of my price range, I will keep my eyes open for somthing cheaper. So would you guys recommend for me to put those 351 heads on my 302 for now while I build my motor this summer or is it a waist of time? Back in the carb days was there not an advantage to taking stock heads off of a 350 and putting them on a 305? When it comes time for me to start getting parts for my 351 rebuild is the complete engine rebuild kit that has all the gaskets, bearings,seals, cam and pistons? what brand of parts to get? What to stay away from?

 

Not the GT-40X aluminum heads, the (3-line) cast iron GT-40 heads or the (4-line) cast iron Gt-40P heads. They are no longer offered by Ford but are available at swap meets and junkyards everywhere, usually for around $500 a pair. The X-heads are very nice (I have a set on my Mustang) but you don't need the weight savings on a truck and may not care about the difference in HP potential between the two since the X heads move the curve up slightly.

 

At peak the 351 puts out nearly 240 HP and the truck 5.0 is rated at a little over 150...the car 5.0s (H.O.) is what I think your talking about. They run at about 230 peak HP. But ya, you're right about the increased drivability

 

Better check your specs Sampson.

240 HP was only for the Lightnings which had the 3-line GT-40 heads along with the Gt-40 intake and T/B.

Stock 351s were rated at 205-210 HP depending on what year and the source of data you find.

150 HP is the rating for the 300 CID I6; the 302 put out somewhere in the range of 195, again depending on year and the source of the data

 

Good call, totally wasn't thinkin there.

 

The truck 302 and the 302 HO are pretty much the same engine with different intakes, cam etc. The car version puts out 215-225 HP the truck is between 185-200. Cant remember the torque specs off hand but I think the car was around 280 and the truck was closer to 300. (just a ballpark here, been a long day and I dont have the energy to look it up right now) The big difference is in the powerband, car HO is mid-upper and the truck is low end.
Also slightly different between the Stang - Cougar/TBird - Vic/GM

But for performance the 351 is a better engine to use in a heavy application like our trucks