My 87 Blazer seems to be having breathing problems.  The engine has well over 300,000 miles and I'm considering pulling it while it's still running somwhat decent.  I'd like to rebuild it into a stroker 383, but can't afford it right now.  Would putting a larger intake on, and replacing the stock manifolds to headers and exhaust system help enough. As a band-aid I guess until I can get the space, time, and money for the full rebuild.  Also, could I get a set of intake manifolds and exhuast that would work for the 350, yet still be adequate enough for when I stroke the engine? Thanks  

With that many miles, the valves may be pounded into the heads.  Even though it has hardened seats, the valves will wear through (origional is induction hardened).  I have seen valves pounded in 1/4" or more.  You already admited that the engine is due for a rebuild, so before doing bandaid repairs check into all the causes of the poor performance.  Example: valves pounded into the seats, excessive carbon build up on the valves due to valve guide worn out and oil leaking past the shot oil seals on the stems, camshaft worn not opening up the valves as much, compression loss due to worn cylinders, rings, pistons and so-on.  I hope you checked the air filter first, lol.  But truely your engine needs a rebuild.  

300,000? Damn thats pretty good!

How exactly do you know it's a breathing problem and not something else?  

I'm guessing that it's a breathing issue based on how it sounds, it just sounds like it's suffocating, bogging down or nearly cutting out when you try and give it some gas.  Last time it was driven there was a noticable amount of exhaust.  Darker colored, maybe oil getting into the exhaust, maybe I should check into the valves and internal components.  What's the best way to check the valves? Do you need to pull the heads? And once we started having problems the air filter came off completely, it was new, and didn't make a significant difference.  Thanks alot.  

oil is bluish smoke, fuel is black,
compression check for starters, can tell you if it a valve problem or just plain wore out, may even be a fuel problem, what carb is on it?  

A compression test is good.  If you have access to a cylinder leak down tester do that also.  I like to do the cylinder leak down test to determine where the compressin loss is.  Both a compression test and cylinder leak down test should be done.  Read my previous post on this issue, there is a lot of good information there.  If it is an 87 it should be a TBI, not carb.  That was the first year that GM put TBI on light trucks.  

I thought it was 87 they switched to the TBI.

a couple squirts of ATF followed by the dry compression test will determine a valve or ring problem if you don't have a leak down tester.
a valve problem will generally have low compression either way, while the ATF will seal the rings unless there is a busted one.  

Good point on the oil in the cylinders.  Dry compression test first, and then wet compression test.  I have not had to do the wet compression test since I bought a cylinder leak down tester.  

I agree, the leak down is better, I've still got a little redneck in me.  

Thanks alot. I'm going to take care of it after I get out of the desert. I'll post how things go.