I've got a 289 crank and rods and a worn out 302 I was thinking why not put it together and see if I can squeeze the most possible mileage out of it

It's a single cab 5 speed 4wd mostly used for frequent long road trips hence the worn out motor I've gotten 19 mpg out of it but now it has a crack next to the 02 sensor so it's like 12 regularly

I got headers to put in with the new motor I was planning on milling out the smog whatevers in the exhaust ports and getting rid of the exhaust thing in the back of the heads (I haven't dug into 80s-90s engines in a looooooong time) plugging it with 5/8 18 bolts like I did with my other truck

But basically higher compression pistons 289 crank roller cam headers and ideally I get the same performance as the 302 but with less gas used and pistons moving slower to help increase ring life and lower parasitic losses

What does everyone think of this idea

P.s. it does like 90% highway miles

 

Well, a 289 would be a bit small for a truck ( the 302 is small in my opinion) but if you use the factory 94 and up roller cam you would probably be ok.
I wouldn't go any bigger than the factory roller since you are going down in displacement it will make the cam ACT bigger.
Upping the compression will help just make sure your pistons are absolutely zero deck and run a .038 to .040 thick head gasket and you will be good.
Just know you will win no races and hauling weight even what the door sticker says will be a task.

 

I'll bet the 289 will still beat the 300 in power as its 13 cubic inches or ~3% smaller and the compression is just to make up for the smaller stroke

But yes I know about towing because the 302 was held floored in 2nd to haul my jeep up devils canyon whereas my 75 did it with a heavier vehicle in 4th gear while running on propane

 

Another thing you could consider is gearing what gears are in the diffs currently?

 

3.55 in the front I had a dire need for a rear axle so I grabbed one that should be 3.55 I have yet to check but regardless I like 3.55 gears they keep it at like 1700 rpms at 55 so

 

Well those are better than 3.08s so that's good.

You planning on using your current roller ready block or getting a different one?

 

What years are roller ready I assumed all of them but now that you mention it I'm second guessing myself

I know the block it has is older since where it says 5.0 on most blocks this one says 302 plus I have one more useable block that idk where it came from

Any idea on what heads I should use I have like 4 sets now one came with the 289 and I can't remember the numbers off it but they weren't considered good heads they may have been for a motor other than the 289 as it was just parts someone had laying around

 

Pretty sure 86? and up mustang blocks and 88 and up truck blocks were roller ready. They will have these threaded holes to bolt down the retainers.

As for heads, that depends on what you want to do about pistons. The speed pro piston book I have doesnt list a hypereutectic piston for a 289 that has more than 8.6:1 compression with anything other than a 289 head. And those dont flow as good as the newer e7 or gt40 heads, and I think they have a slightly different intake bolt hole pattern. BUT, the forged piston section shows with a gt40 head 10.2 :1 so you may want to do some shopping around for pistons before undertaking this project.
A set of gt40P heads and a .030 over bore would get you into the 9.0:1 range. But you will need to run long tubes and massage them.

 

I'm about 80% sure the 289 and 302 use the same pistons and the difference is made up for by the longer connecting rod in the 289 so actually finding some pistons shouldn't be an issue

What kind of compression would be best here

 

I will have to check my book after work and see if part numbers tell if pistons can be swapped. As for compression, I would shoot for mid 9s and have a tight quench (.040 at the most)

 

The stroke is an 1/8 inch shorter the rod is a 1/16 so it should fit based on the math

 

Right, but the swept volume of the cylinder remains the same. For instance, speed pro h273p is a 289/302 piston. But in a 289 with 58cc heads it makes 8.62:1 compression. While in a 302 with the same head it makes 8.9. And that's with the 8.206 deck block. The 73-76 8.229 deck it would be 8.5

The p/n L2482 in a 289 with a 60cc head makes 8.9 to 1 and the same piston in a 302 makes 9.3. So some research into a good head to bring compression up may be needed

 

My jeep also needs a new motor so maybe I'll just do the 302 and then do a 289 for the jeep