I mite have asked this before but I need some new advice from this group ,I have a stock 273 from 64 and I have some early 70's 318 heads can I use them on the 64 block and not have low compression tahnks

IF the 318 heads are open chamber and the 273 heads are closed chamber, you will lose quite a bit of compression. i'm not sure but I think 273 heads are closed chamber. Do some research om the casting numbers and you will find out if they have different chambers.
A short cut is the fastest way to a place you didn't want to go!

I'm almost positive the 273 heads are CC so as BBcuda said you'd be worse off. what about locating a 318 or better yet a 360? (& the 360 would only require a slight mtr mt adjustment for fitment & the B&M 10239 flexplate), small price to pay for the very significant gain you would experience (especially with the 360)

Really the early '70s 318 heads will not increase power and may actually decrease it. They don't flow much different and the chamber will be bigger.

Magnum heads would be the best swap, then the late 2-barrel 318 heads with casting number ending in 302. The 302 heads have hardened exhaust seats and basically the same chamber volume as your 273 heads. You can port either head. believe class racers have said the early closed chamber heads can be made to flow better than the 302s.

273s don't get much respect and some of that is economics. They are more expensive to overhaul than a 318 and people are basically giving 318 blocks away. I have been given three, two being complete engines. I would suggest finding a 1986 - 1988 Fifth Avenue as it has the roller cam block and the 302 heads. That 45 cubic inch or 750cc increase in engine size will do about everything better than a 273. And those late Fifth Avenues usually led sheltered lives.

R.

Bit more than that, early 273's have a slightly different driver's side configuration and the old 1/2" spacer on a 360 trick doesn't fit it all, you need to weld an ear on the MM as well. See pic. Schumacher Creative has the swap mount for those of use that cannot weld (me). My 65 273 is meh in the power department, so I upgraded it to an 87 318.

thanks just wondering if it was worth the effort I think ill sell the crank to a 340 guy thanks

Save the rods...I like running them better than the factory 340 rods...

The rods are floating pin, same as the early 318, 726 grams. Later rods which came out with the 340 were the 496 or 645 rods, thicker shank and weighed 758 grams.

Both are at least 100 grams too heavy.

I'd keep them with the block and pistons, if you sell the crank. BTW, the 273/318 forged crank is different than the 340 crank, as the 340 crank has lightening holes drilled into the #1 and #4 throws.

R.