I have the chance to buy a 340 1-19-71 Block. It has NO heads and no intake. All pistons, rods, crank, cam, lifters, timing chain and cover are there. It was sitting and rusting like that for years and years. The owner was given the block in that condition with no knowledge if it ran or seized. He is asking $650 for it. Question is it it worth taking the chance that the block might be cracked, too rusted or seized?
On a side note can magnum heads bolt on this 340, or should i stay with original 340/360 heads with 2.02 intake valves?
thx

No way, not without a tear down, magnaflux, and core shift check from a reputable machine shop (roughly $200.00 in work for those checks FWIW). They are thin wall blocks so over boring by .020/.030 is risky due to that and that core shift problems could make it even worse. Also common were hot/cold stress cracks in the lifter galley area. Yes, the magnum heads will work on a 340 as long as you use the appropriate intake.

Too much $ to take a chance on.

If it is that rusty, it may have frozen & cracked internally.

Even if it checks out to a sonic test that is too much for a core.

Yeah i knew it was high just wanted to be sure, i just saw how to post some pics of it just to make sure.
What would you offer him or would you not even chance it?
thx for the response guys

Another pic

Measure a bore, if it's stock bore, offer him a $100 and walk away if he doesn't take it. Too many 360's out there.

It's low compression so it may be a cast crank. That's a $100 motor. They are just to thin and this one is rusted. the lifter bores are rusted, too. I sold a std.340 short block with a steel crank to a friend for 600. The last complete std 340 steel crank motor I sold, I got $1000.

I never had a problem getting good money out of the early stuff. (68-70) Not so much with the 71 up.

That's crazy money for a rusted late 340. No way I would even consider that block with all the rust.

I stored a complete 340 in a spare bedroom in my house for 23 years so it wouldn't rust. It got dusty but that's it. In 2007 I took it apart and replaced the original heavy factory hi compression pistons and it has been in my car since.

Keep looking, I think there are plenty 340 and 360 blocks still out there.

As said run do not walk away from that deal. Money talks and there are alot better deals to be had out there. In addition it's common for a person to start on a project that is too far from completion in one or more areas (drivetrain/bodywork etc) and it takes them months/years till they are finished and actually driving/enjoying the project. Depends on how much money/time/energy/friends/equipment/resources a person has at their disposal. Look at the big picture/make the right overall decision & good luck

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Early 10.25 340 pistons stick out above the block deck, so you can't use them with closed chamber magnum heads unless you use really thick head gaskets. I'm not sure about later 72-73 340 pistons, if they are below deck they may work with Magnum heads. Edit, looked at pics above... late "smog" pistons in an early 71 block? Something's been changed from stock I think.

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I was answering his question directly, as in, will the magnum heads work on a 340, answer: Yes they will (with other changes).

Who on earth would re-use a 40 year old used crusty azz factory piston in a new build?

The worst part of the bores will be right where you can't see ,, the piston ring area may have deep pitting . 340's are getting hard to find but I'd walk away from this one