help with 273

Some good discussion here. Since the 273 and 360 are the same size externally, it is possible to make a 360 look like a 273 without a lot of effort. I'm particular to the 64-65 273HP exhaust. It's the wildest sounding single ever in my book.

Simply because the 360 produces more power, I've found that people are asking more $s for an assembly than for a 318. Apart from the acquisition cost, the 360 will produce more power-per-$ than anything.

The 68-71 340 is the best power producer as it has all the goodies and high compression. However, it is scarce and expensive when found in decent condition. These things were flogged hard so there is a lot of junk out there.

5 Things that complicate LA engine building:

1. The 64-65 intake manifold bolts are at a different angle than later years. Some aftermarket manifolds are able to accomodate the difference, most don't. It may be necessary to use later cylinder heads to be able to use the desired intake setup.
2. All LA forged crankshafts are not created equal. The pre-68 273s used a forged crankshaft as did the 68-72 340. The 340 is balanced for the HD con rods, the 273 used the light duty rods. Balance reciprocating parts at machine shop.
3. It is my understanding that all of the 273 forged cranks were drilled for the pilot bushing. None of the cast cranks destined for use with automatics had the pilot bushing drilled out. A machine shop can do this for you.
4. The intake gaskets in most overhaul sets will not allow the intake to seat properly. A soft, thick gasket will correct the problem and prevent big water sprays under the hood.
5. The driver-side LA engine motor mount is different between the 273-318 and 340-360 blocks. The third world solution is to shim the difference with flat washers. A more secure solution is available from Schumacher Creative Services.