Ist it possible to put 351W heads on a 302 and if so how hard is it complete and what does it take? Also what would be the benefits to doing this?

Thanks

 

The 351 heads will bolt on a 302 block, but you will have to buy ARP speciality bolts for the swap. The 351 uses 1/2 inch bolts while the 302 uses 7/16 inch bolts. The bolts you will need have a 1/2 stepped down to a 7/16. This will allow proper alignment of the head. If you are going to use the 351 heads be sure to get a decent set from the late sixties and not a set of smoggers.

 

'69-'70 351W heads are the ones to look for; but don't expect a tremendous hp increase. The exhaust ports are virtually identical to the 289/302 heads; which is to say, quite poor. As mentioned, 351W heads will need special bolts. Later 351W heads are virtually identical to 5.0L heads in both port and valve size. To really get any benefit, you need to port them, install larger valves and hardened seats; but then you're looking at more money than a set of GT40-P's would cost you.

 

There is a special "stepped washer" you can use with your existing head bolts.

 

7/16 Hardened washers will work just fine and they are alot cheaper than specialty hardware, the head bolts don't locate the head anyhow. Use the 351 intake gaskets, the water passages in the intake manifold are different, and don't worry about the two extra intake bolts in the 351 heads, also the water passages in the heads are different in one location in each cylinder. Use the 302 head gasket and you will have to use a drill and add the extra holes in the 351 heads. There is a half moon shaped hole in each cylinder in the 302 head that isn't in the 351 head. I've been told you only need to drill one hole for the half moon shaped water passage in each cylinder, but I would take the time to drill each end of the half moon and then use a dremmel or an air grinder to complete this half moon shape. I would hate to get it all together to find out later that you should have done this before you put it all together. I would also go with adjustable valve train. You might want to think about hardened valve seats too, as these heads didn't have hardened seats in them. Also, spend the extra money on good quality gaskets, it's cheap insurance. Another tip, if you are going to modify these heads very much, you will be cheaper off spending the $800 on a set of World Castings 180 heads. Also, watch your compression ratio, the 69-70 351 heads are 60cc combustion chamber heads.
Good Luck !!
Dave