I have a 1966 casting 289 engine and a 1979 casting 302 engine. From my research, both blocks have the same 4" bore cylinders. Based on looks, the 302 heads seem beefier. Granted, both blocks would need to be bored and both set of heads would be ported, but I want the best base setup. I am planning on using the 289 block, being it has a smaller stroke (higher compression) and mate it with the 302 heads. Am I correct that the 289 has a smaller compression? And is this a wise combination?

 

Regarding longer and shorter rods and related compression between the 289 and 302, read this info to see if what you want is either a longer rod, or a shorter rod. Maybe this will help you decide on the head question.
http://victorylibrary.com/mopar/rod-tech-c.htm

 

It appears to me that you have more research to do. The compression ratio is Vb/Vt where Vt is the volume of the heads + head gasket thickness + volume between the top of the pistion and the top of the cylinder when the piston is at the top of the stroke (may be positive, negative or zero, also varies with piston style). Vb is the volume with the piston at the bottom of the stroke (stroke*pi*bore/4) + Vt. For the 289 the volume of the cylinder is smaller than for a 302 since the stroke is shorter. Thus, if everything else were equal the 289 would have a lower compression ratio than the 302. But everything else is not equal. Ford changed the heads from 66 to 79. IIRC the volume of the head in 66 was about 54 cc and later engines had larger volumes (~ 58 - 62). So putting the 302 heads on the 289 would decrease compression ratio. Look at this chart
http://www.mustangii.org/tech/head-interchange.shtml

Plus IIRC the 79 heads were designed for emissions and may not flow as well as the earlier heads.

Of course you need to look at the entier package, including the flow rate of the heads, valve size, cam specs, pistons (pop up or flat tops) etc.

I'm not saying that you shouldn't mix and match blocks and cylinder heads, just that finding the right mix is more complicated than what you indicated in the original post.

 

a friend of mine is having a 6 fastback gt350 clone built and he is build a 302 for it with 289. reson behind the 289 heds was that they have more meat in them that can be ground out when porting and polishing. the 302 heads you cant port as well. the walls get too thin and weak.

 

Sorry to resurrect this thread, but does anybody know where to find something similar, except with casting numbers?

Dave

 

There are a few books around for small-block Fords that will include casting numbers. Just about every Mustang specialty house will sell these books.

 

if you want the same compression just get the gt-40 heads and mill them down so you have the combustions chamber of you choice