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OK, I am here long enough to give you another real idea. But first some reality...
The 273 and 318 heads use the same intake gasket and for the most part were the same castings. The first two years of the 273 had the intake bolts at a different angle but everything else is the same. 340/360 heads have the same port face with the same bolt holes and the ports are on same centerlines, but they are bigger. For a street engine you could put that intake on a 360 and it'd run great. So that's an excellent idea. The port mismatch isn't nearly as important as one may think. For that same reason a popular swap on 318s is a 340/360 stock intake, they are cheap and make a lot of power. I have one waiting for my 318, $15.00 at the swap meet and it even has nice paint on it.

But back to the Offy.....Put it on the 'bay and list it in the classifieds here for two months. No one will even give you a call. If you can get a decent price, like $100, sell it to them, take the $ and put it towards an intake you really want.
After two months you will get tired of it, and aluminum prices are in the dumper like everything else, worth $12 for scrap. It'd be a shame to throw it away. Instead, you get a roller cam 318 like the one from my mother's 86 Fifth Avenue that's sitting in my backyard. Put a 4" stroker in it (optional). Port the 302 heads by yourself. Either plug the holes in the head and drill to your intake's angle or angle-slot the intake holes. You are enough of an artist to not ruin the intake by changing the angle of the holes. No need to "wallow them out" they just need an angle shift. Then regrind the hydraulic roller cam and run two 400-500 carbs. It'll look cool, run real strong up to the cfm limit of the heads, and you'll be the owner of something different. 318 - 391 cubic inches will be big enough to get you into orbit in your '38.

If you REALLY have to run 273 heads because you want to keep all the original bolt holes (I don't know why you'd want to do that)then get with some of the 273 drag racers here to get the best porting tips. They will work too, but I like the 302s better.

Either way do not saddle yourself with a 273 block unless you are a class racer. 318s are free anyway. The cost and difficulty of doing a right 273 rebuild make it a losing proposition.
A 318 is exactly the same everything except the bores let the heads breathe better and the extra 45 cubic inches will make a lot of extra power.

Good Luck,
R.





On the 302's, we have flow number comparisons that show the stock 920 outflows the 302. With the same mods done to my 920 (stainless valves, bowl blending etc.) the comparison with the 302 still shows the 920 outflows the 302 with the 302 falling off just before .450 of lift. The 920 dosenty fall until after .450. As far as cost to do a 273, I've put together quite a few 273's and compared to the several 360's I've done the costs are pretty much the same. It all depends on how much machine work is needed. Of course if you go with forged pistons on the 273 the parts will be a little more. With the cast flat top piston, 9 to 1 to 9.5 to 1 is fairly easy on the 273.