The DOOE 351 heads will fit just like the origional heads, except you'll need, either stepped shoulder head bolts or bushings. There should be no fittment issues with intake or exhaust. The larger combustion chamber, will reduce the compression ratio. My old 302 was built using the DOOE's (ported) and pistons that restored the comp ratio to 9.5
If you need bushings the Trick Flow TFS-51400419 Head bolt reducer bushings@$29 are the better deal than ARP, or Edelbrock, and will work exactly the same.
As the man said, The issues are getting the compression ratio up by either milling the heads or using a higher compression piston and the bushings due to the difference in the head bolts.
Are the bushings really required? I'm asking because I installed mine without them, and just used the regular head bolts with hardened washers. Problems yet.
Are the bushings really required? I'm asking because I installed mine without them, and just used the regular head bolts with hardened washers. Problems yet.
The 302 block is set up for 7/16" head bolts and the 351 heads are drilled for 1/2" head bolts. You can see the need for the bushings or stepped washers. The head alignment dowls are the only alignment you've got working, and even hardened washers will deflect, & your bolt torque can change.
I honestly don't know if I'd freak, & do a tear down. But I won't install my GT-40X's without the bushings.
Another option was to purchase a head bolt set from Ford Motorsport that had 1/2" shanks with 7/16" threads. These were made to install the 351 heads on the 289/302 blocks.
I found this out after having bushings install in my 351W heads years ago.