I have talked now to several different people about this topic, and Have not really gotten any answers. Aside from the 302s reputation for cracking how are they compared to the 67 273 heads.

I believe the 67 273 heads are 920s. At anyrate, they are also a closed chambered head and have roughly the same Chamber size and the same valve size.

Does anyone have any flow charts or information about each of these heads to make actual comparisons.

I am not sure whether to have my current heads worked a little, or just to start with a set of 302s and shelf the current ones.

I'm in the same boat & just getting started on this as I want to get some closed chambers for a quench low rpm mileage 318. Since you shared that they have the same valves/ports and that the 302 are crack prone I think I might go w some 273 ones & bowl hog the heck out of the bowls & call it good.

Well, if you are looking for a set of closed chamber heads...Mine may be on the market in the next couple of weeks. I just got a call from a buddy tonight, as luck would have it, that he would sell me a freshly rebuilt 318 at a good price. He is willing to sell it for less money than it is gonna cost me to re-cam and work the heads on this 273. Apparently this 318 is around 300hp as it is, way more than what my 273 would ever have. Anyways... I have not 100% made up my mind on it. But if I do I'll PM you about them.

BTW, are you the same Rapidrobert from the /6 site?

One of my best friends has a 65 Barracuda with a 273. It has a "Mystery cam" in it (Came Hyd. with stamped rockers in place) and he is now running some 302's he port matched to an old cast iron 340 intake I gave him.

No real #'s on it, but the car launches like a scalded cat which is impressive thru the stock exh. manifolds.

The 302 will flow less because of the even bigger bulge in the intake port caused by the pushrod hole witch is larger because of the PR angle in the roller motors. How much is anyones guess , no one really runs either of these heads in a build that can afford a flow bench.

I would not worry too much about the hardened seats myself as I ran a 68 273 for years beating the crap out of it 85 octane no lead and the seats were fine when I finally tore it apart, as a matter of fact I see worse seats on a lot of the magnum heads than any of the older non hardened seats. I have heard the reason for this is the mopar heads have more nickle in them than the other makes and it helps with the receeding seats.

well also, running 85 octane probably kept the temp down a bit. I am sure you're right too, high nickel content probably helped with not only strength but also has a higher heat tolerance.

Another thread said something about how when the valves close and open they tear some of the seat off from tiny spot welds. If the block was closer to the relative strength of the valve, i bet you would have less of that.

I didn't ran lead substitute in my first small block. I was running lead in my 273. I just recently pulled apart the first one, valves look fine. I am no longer running lead in my 273.

If i had a rare, expensive, or high output engine that for some reason did not have hardened seats...then i'd run the lead again. But at about an extra 8-10% the cost of a tank of gas for lead substitute, i can pass for the time being.