I'm rebuilding a mild street motor for my maverick. I have a performer rpm cam and intake manifold ready to put on. My question is soncerning the pistons and heads. I have 2 302s, one is a 68 and one is a 74. I was thinking that I would use the 68 pistons for more compression, but I was wondering if the heads were any different? -Ford Guy
Assuming that the block doesn't need bored, and that the '68 pistons are flat-top and not dished, I would use the '68s. The heads are the same as far as combustion chamber size, valves, and ports...
wgy not just chectk the compression in both? im willing to bet the 68 has more power, at least it would have from the factory. who knows 40 years later. good luck
I've seen '68 302 2-V heads with 63ccs, where the '69 or '70-'76 had the 58cc heads. You could easily tell the difference with them side by side looking at the combustion chamber.
Is the block decked higher on the 74 block? I know the compression is 8.0:1 on the 74, so definitely go with the 68 pistons.
You're talking 40 year old stuff here. My recommendation is getting the casting numbers off the block, heads, crank so we can see where we are. You could very well have a 68 block with 74 heads or a 74 block with 68 heads. Or any other combo out there including stuff that is essentially junk because it's been bored too many times or decked or warped. 73 is about when Ford went to larger combustion chambers and the resulting low compression. Casting numbers will tell the tale, along with cc-ing the heads. Generally, you can tell the cc range by looking at the combustion chambers. If they look like D, they are the big chambers. If they look triangular, or have an irregular shape around the sparkplug, then they are the smaller chambers. For best power, you want the early heads. Now, remember, neither of these heads are going to make big power. Ford was more interested in efficiency and longevity than power in those days. No stock windsor will rival brand X heads without extensive work (and money). I'm sure I get some disagreement here.
We already have the 74 block cleaned and honed, I was just wondering which heads were better or if they were the same.
If you use the 68 heads you will also need the 68 pushrods. The 74 ones are longer and will snap the rocker studs. Been there..done that. Steve
No. You want to use pushrods for the year of the block, not heads. In the early 70s Ford toyed with the deck height of the 302 block, and that would be the only reason I could see them varying the length of the pushrod. The head thickness or mounting height of the rockers was not altered at all from 68 to 74. On the heads, there is probably very little difference, if any between 68 and 74. Ford was using piston dish and deck height to vary compression ratios over that time period. Drastic and unhealthy changes in heads didn't come about until around 76, when all SBF and Windsor heads became identical and smogged up. IMO both the 68 and 74 heads are pretty lame. Only the hermaphadite 76-up heads are worse IMO. Only after 87 did Ford heads wake up some. 289 heads raise compression, but don't flow better. 351w heads (69-73) are the best bet as they flow better without losing compression. 74-75s are same, but have more smog plumbing to deal with.
The deck height of the 221/260/289/302 blocks remained the same at 8.206 from 1962 to 1977 and on into the 5.0 to 1998. Only the Boss 302 had a slightly different one at 8.209. 351W deck heights did change in 1971 from 9.48 to 9.503.
However, 302 2v heads for 68 show 63cc chambers. The 74s should be 58cc... If he uses a taller block and 63cc heads, he could end up with a much lower compression ratio than he would like. Just a thought. All numbers should be checked! I just glanced at a Ford reference for the head CCs, but the casting numbers could vary, which would vary CCs.
