Are you guys sure that 25hp increase isn't from a 240 head replacing a Seventies-style 300 smog head? The smog head was a pretty sorry piece, but the efi swirl head works a lot better.

 

5 year old thread, the guy making the +25 claim has not posted in over 2 years. We may never know the answers here.....

 

Can one obtain a 25 horse increase just from changing stock heads? Seems a bit optimistic...maybe even a fantasy?

 

With the 240 head you should get much more torque! The combustion chamber is (I think) 50 cc smaller than the 300. That should contribute to more low end torque right?

 

Not 50cc smaller. This says 8cc:

FORDSIX PERFORMANCE ? View topic - 240 head on a 300 ???

76 vs 68:

https://www.ford-trucks.com/forums/1...entiation.html

another pic, most say .5 of a point of CR with the 240 head. Yes, compression makes more torque.

https://www.ford-trucks.com/forums/1...ification.html

Also, long thread here with discussion on the whole stroker thing for a 300. Short version: No.

http://fordsix.com/forum/viewtopic.php?f=2&t=58663

 

Assuming a vehicle is old enough that the authorities don't sniff it anymore, replacing a '70s-style open-chamber smog head with either a '60s-style closed chamber head or a mid-'80s-up swirl-port head is always a winner for efficiency through the ability to build in a little more compression. We've just been talking about this on another current thread, "'68 F100 insline six build-up," in relation to the Ford 400M V-8, an engine with a lot of potential (same 4"X4" bore/stroke as the 300-six) that was always limited by its smog heads. As also mentioned on that thread, the 460, which was actually fairly efficient for a monster V-8 even WITH its smog heads, could be upgraded effectively and cheaply with a set of closed-chamber 429 heads.

But there's a caveat: if you really want to get the full efficiency advantage of closed chamber heads, and build in the most compression increase that still doesn't cause ping when hauling a full load up a steep grade, you have to set the squish-height to a recommended minimum, and this requires shaving the block deck . . . which means you tear the motor down completely, take measurements, spend money. If this sort of thing, doing a full overhaul and upgrade of your engine, strikes you as a big hassle rather than a cool, fun thing to do, well, you're never going to get the full advantage of a head swap.

So when you see a figure like, "gained 25hp from these heads," you need to ask some questions. Same deal with aftermarket parts; when Edelbrock or Clifford or whoever says their part can gain you XXhp increase, they probably aren't lying, but you have to do the whole job right. A whole lot of guys are on the internet telling us how they were disappointed after installing parts or making other changes. My guess is that they didn't do the whole job right, especially the re-jetting and the re-curving of the spark advance curve, but also maybe something kind of obscure like setting the squish-height. I was very lucky to have squish explained to me nearly fifty years ago by a couple of smart engineers who raced outboards when I did. They were way ahead of the game, and "squish" only became a buzz-word among car-guys in the last, what, fifteen years? But it's one of the more important blueprinting tasks in any good engine build.

 

Every single difference between the 240 and 300 head: 240 and 300 Cylinder Head Differentiation

 

Thanks for that; it'll be a good resource when the bugs get ironed out (it's a wiki!!). Having Frenchtown Flyer, who was a Ford engineer and is a Ford racer and rodder, as well as Number Dummy going through it is a huge plus for the rest of us. Thanks for getting it rolling.