When did the spark plug size go from the large 13/16 plugs to the smaller 5/8 ones? My other 302 has the large plugs, so I'm thinking they're probably 289 heads. The motor is on the stand, upside down, covered up in my storage room and I can't get to it to check numbers on the heads and block. IIRC, I ran the numbers on the block once before and it was a 70 block, but I'm not sure now. It has a three bolt 28oz balancer, so it might end up being a 289 instead of a 302. Doesn't really matter one way or the other which size it is, as it's going to be a cruiser in the street rod anyways. Just wondering mostly about the heads, if they are the small chambers or not and if the big plugs will give problems with header fitment.
I think '74 or '75. My '75 had the smaller plugs, put on some '72 heads & they were the big plugs. My '73 had the big plugs too.
Just remember, none of these heads flowed well. It does'nt matter which set of stock heads you run. If they were not the DOOE heads, none of them flowed better. It doesn't matter if the combustion chambers were smaller. The DOOE heads, off the 351W 4V, were the only heads that flowed margionally better than any of the other heads. No matter if they were the 289 power pack heads, or what they were. The only small block head, besides the tunnel port 302, that flowed any better, was the DOOE heads, that came off the 351W 4V engines. The old 289 power pack heads off the Shelby, even flowed less than the 351W 4V heads. Yet, they worked good on the little 289. I venture to say, that a set of gasket matched, 302 heads will flow more than those 289 power pack heads. The 289 power pack heads had very small intake runners and exhaust port volume.
^ Reread original post. Not looking for flow or HP on this motor, it's a street cruiser only. Just curious about the plugs, and possibly the chamber size for the compression ratio. Don't want a cruiser that I have to feed race gas!
Ford went to 4 bolt balancer in 1970. Most 289's had a thin harmonic balancer. The 1968-69 small blocks had a wider balancer with more detailed timing markings.
