150 HP LA 318 - vs - 230 HP Magnum 318

[YY1]

BTW- ZOMBIE thread.

 

[318willrun]

91 5.2 is a Magnum and was rated 235 HP with the "large exit" Magnum manifolds.

Rating went down to 230 with smaller outlet manifolds.

5.9 was rated 245 HP and was the same as the first gen "crate" 360, rated at 300 gross HP.

Just a note - first year of the 5.2 magnum was '92. '93 for the 5.9 magnum.

 

[YY1]

Just a note - first year of the 5.2 magnum was '92. '93 for the 5.9 magnum.

That's correct, I meant to type 92

...but the 91 was not rated 230 HP as posted above me.

 

[toolmanmike]

Not correct. The LA 318 was rated at 230 horsepower

I wondered about net and gross. I didn't know LA's were ever rated net but there's a lot I don't know, and I didn't realize there was such a difference between the two.

 

[318willrun]

I wondered about net and gross. I didn't know LA's were ever rated net but there's a lot I don't know, and I didn't realize there was such a difference between 230 and 180.

1972 all HP went to net. In '71 the 318 was rated at 230 hp, in '72 it was 150. If you look at HP charts, a big drop in HP ratings on all engines from '71 to '72

 

[273]

I wondered about net and gross. I didn't know LA's were ever rated net but there's a lot I don't know, and I didn't realize there was such a difference between the two.

Net is dyno like the engine exists in the car breather exhaust tune etc... Gross is how most performance built engine we talk about are done pretty open to the conditions on how you want to test it.

 

[volaredon]

I don't think the 318 heads are necessarily bad, it seems they flow better than a lot of Fords 302 heads but 5.9l/360 heads are just gonna give you a big jump in power, other than throwing a cam 4bbl exhaust on a running 318, I don't know why people insist on running 318 heads when looking for power. I bet if all LA 318s came factory with 360 heads since the early 70's people would have a way different view on 318 performance potential.

360 heads only serve to make an already low compression ratio even worse.

 

[273]

360 heads only serve to make an already low compression ratio even worse.

Didn't say don't do anything about CR, a slight milling gets you 318 chamber size, or better yet use proper pistons. There's many ways to get there but starting with 5.9l/360 heads are gonna get you at least 40+ hp neverminded aftermarket ones. Why do think the factory did that with the 5.2l magnum, to get the power number up to match modern time power levels.

No matter what you do to 318 heads you can get better results doing similar with 5.9l/360 heads. Even if your goals are modest you'll need less cam to get there which will be more streetable overall. For the price/performance speedmaster should basically be the starting point for pretty much any build.

 

[toolmanmike]

Closed chamber 273 heads, like the 920's, would increase the compression a bit (one point at best?) while still using the small 273/318 sized valves and ports. The 340/360 heads reduce the compression a small amount (both are open chambered but I bet the 340/360 chambers are a bit bigger) That trumps a little compression every time.

 

[YY1]

Also, for the 8.8:1 318, a factory replacement piston for a 9.2:1 engine (1967-69/1985-91) should be pretty easy to find.

I believe they are different because of the heads, but math using the installed height and head chamber cc/gasket thickness should get a quick final ratio number.

 

[66fs]

If you are swapping heads, you should mill them flat and do a good valve job anyway. Perfect time to get the chambers where you want them.