I found a 68 302 for sale with 289 heads,,he says there are 54 cc..what kind of compression will it have with flat top pistons?? will it run on pump gas..the headers are 6901 hookers,,will they fit 73 maverick??
you'll also need to know the deck hight of the block and if its been bored out any 289 heads are the same as 302 heads, the only varaibles are the combustion chamber and valve sizes. you need to know all the pieces of the puzzle to figure out a compression ratio
'68 302 heads had 58cc chambers and 9.0:1 compression (roughly) so i would guess around 9.5:1 with 54cc heads, but like Tony mentioned, the 289 heads have smaller runners and valves along with smaller chambers. as for the headers, 6901 hooker's fit very well in Mavericks/Comets.
Check the 68 carefully. My cousin's 289 has 302 stamped on the block, 1.78 and 1.45 valves with a 289 crank and rods. 68 got some parts swapped around in the mix, and yes, his car was 100% original when he got it. 289 deck height should be the same as a stock 302, not counting the odd 73-76 years.
The comp ratio also depends on which 302 flat tops you pick. They're not all the same pin height. That varies from 1.585 to 1.619. That's almost a half point in the ratio. Early 289 heads had 54 cc chambers (like the C6OE's) The later ones had 64 cc chambers (C8OE's) That's another full point difference. Depending on the heads and pistons the ratio can be anywhere from slightly less than 9 to 10.5 to 1.
Finding used 289 heads without knowing the history could've been shaved a time or two in its life. Shaving heads was common practice back in the day. You should have the cc checked then you will know where you stand. Gasket thickness will play a big part on the CR
