I want to replace the 305 I have now with just a different short block. If I retained everything from my current setup including the ported 305 (58cc) heads, would I be able to get away with just putting another larger shortblock under it and just burning a new chip. I am thinking that the compression ratio would be a little high on a 350 short block with stock style pistons but I am trying to keep it simple and modify as little as possible until I can get some more money for heads.
all mods are in sig.

There's what you "can" do, and what you "should" do.

Yes, you "can" put a 350 shortblock in there. Like you said, compression would be quite high, unless you used dished pistons. But, you don't want dished pistons if you later put on 64cc 350 heads, because then your compression would then be too low.

The best route would be to either build the 350 to use the heads you have now, or wait on the 350 until you can put it together to use proper 350 heads. The latter is the better bet.

Yes you can do it fine, if your going to have the stcok 305 heads your going to bump compression way up probably around 11.7, that would be with -7 flat tops. Myself I'd run the edelbrocks ETEC 200's if i where you using the 64cc head...

what would be the bad part about running high compression provided I can burn a chip for the fuel needs?
I understand that the 305 heads would be bad for the 350's VE but the compression could only help performance considering it would still be under 11-1.

I am not arguing here - just trying to find out if I could do this without damaging the new shortblock.

There is only so much you can do with the fuel and spark curves to make up for a too-high compression ratio. I believe that, quite simply, it would just not work with 92 octane, iron heads, and a mild camshaft. The cylinder pressure would cause detonation that could rip apart the engine. I agree with five7, find yourself some larger chamber 350 type heads, which may (depending on the porting) outflow the 305 heads anyway. Since you are putting in a new block anyway, it is the perfect time to put on some good heads, not the time to compromise. I wish i had done it this way, but i needed an engine quickly to get it back on the road .

the bad part about all that compression is the stock tpi is designed to boost volumetric efficiency at low 3000-4500 rpms that really will compound the the too high compression ratio problem into a rattling beast that without some really high octane fuel to control it, wont be much fun to deal with. and, well lets not get into the valve diameter compromises made to put those heads on a 305 sized bore. you have a 350 now and should try to take advantage of a few of its stronger points-compared to a 305-one being the ability to run some decent sized valves easily. besides a fresh set of heads keeps the combustion pressures where they belong-and you will have new rings doing their end of that job on the bottom do the same on the top end too. i dunno if this is what you wanted to hear but i hope it helps-just my 2 cents worth.

thanks for the replys guys I really appreciate the straightforeward advice. I will save until I have enough money for heads too.

That's my question. Let's say I got a 350 longblock motor, nothing but stock, maybe a mild cam. I have a 305 now, would a 350 work with all of my original TPI stuff? What exactly would I have to change? As far as the computer goes I mean....

Yes, I admit, I know next to nothing about this TPI. Except that you can't buy a brand new tpi motor from GM anymore, since they don't offer it......

Where is a good place to go to learn about TPI. What you can, and can't do with it? As far as a hotter cam with a 350, how hot could a person build it, and use TPI on it?

well as I understand it :

The problems with just putting the 350 block underneath 305 heads is that you compression ratio would be too high for pump gas.

everything else is secondary to that.

now if you go with some 350 heads then youre fine because thats the only difference between the two factory long blocks. from the intake manifold up is all the same. other than the chip which you could replace with a 350 factory one from that year.

NOW if you want GOOD heads and a bigger cam you would want to have a chip burned by someone who knows alot more than me.

but the mechanical stuff is pretty straightforward.

Oh, ok. That clears it up a little bit. That's what I'm currently thinking of doing. And I was thinking of getting a longblock (they DO come with heads don't they?) anyways, I was planning on using 350 heads, not the 305 ones.

Now I just need to find out how "hot" I can have this 350 built, and still use all of this TPI stuff.