1981 corvette help
 

I just picked up an 81 vette for 4700 and was doing some research and they came factory with 190 hp and an 8.2:1 compression ratio? I think that's embarrassing for a vette, but my question to you guys is, is there a cheap way to bump up compression?

Welcome to the site rm1sner. The fastest and the least costly way to raise the C.R. is to mill the heads. The 8.2 C.R. heads have 76 c.c. combustion chambers and with the dished factory pistons this was the answer to pollution control for the era. I have a stroker engine waiting to transplant into my '78, L-48. I specifically built it with a goal of 9.5 C.R., with flat-top pistons and 74 c.c. heads I'm right on the money. I'm using stock cast iron heads and while c.c.ing them I found one head was 76 c.c.'s and the other was 74 c.c.'s. I had the bigger one milled to match the smaller one, both heads were the same casting number but were one year apart in casting dates.

Do you know the casting number so I can make sure that it is the factory heads?

Just found a guide and turns out that everything from oil pan to carb is factory except the shorty headers...Interior is almost perfect and paint and body is very good. I think 4700 was a good deal! If I mill they heads say .030 over, what else would I have to do and any estimate on what kind of compression I would get them?

Without changing the cam, I doubt a small bump in CR is going to make a noticeable HP jump.

I was wanting to bump up the CR before I put a cam in it but from what I've read, the heads on this thing are pretty weak to begin with.

I was going to recommend going to the big valve heads (2.02" intakes) but thought you were going to limit outlay. There are both hi & lo CR versions of these.

I put 11:1 pistons in and got about 10:1 CR w/ the 76cc heads. Haven't reinstalled yet, still doing front suspension.

Here's some input from someone who has made a lot of mistakes in the area where you now find yourself.
You didn't mention how many miles on the engine,that can make a tremendous difference in your course of action.
Firstly if you mill the heads,,you also must mill the intake manifold so it'll fit properly. If you boost the power to the shortblock,it may not take the strain,when you pull it down to refresh the rotating assembly you'll need to re-ring and if there's any ridge in the bores,you'll need to re-bore which means new pistons and the rods will need to be re-machined.
Do you get the drift of where this is headed? Almost always if you skip one of the steps,somewhere down the road it'll bite you! Mostly in the wallet for a much larger amount than it would have been originally.
At this point it looks like you have a numbers-matching engine which may or may not increase the value of the car now or in the future. Why not pick up a crate motor (which will probably cost less than a proper rebuild on the original),pull and store(properly) the original,drop in the crate motor which you selected at the power level you desire and drive happily on knowing the motor will do what you want. When you sell the car you can either reinstall the original yourself or let the new owner do it.
Of course an increase in horsepower will stress other 33 year old components in the drivetrain,so refurbishments or upgrades will be in order in those areas too.
I can't find my black book which tells me how many 80's were built but 79 was the highest production year ever,so I suspect there were quite a few 80's as well. Point is you won't be modifying an extremely rare Corvette.
So do it! Get after it and make it yours! Hopefully some of my input might help you choose a way that will give you the best bang for your buck. The best way I know to that is to do much of the work yourself! In any project like yours labor costs are always the biggest item,so if you do the work yourself you're paying yourself up to $100 an hour.
Good Luck and keep us up to date on your progress!
Ron

Well said. I put about $1,500 in mine and did all the disassembly/assembly myself.

Another thing when you mill the heads, you'll need to check pushrod length.

rm, I can't remember the castings that I used but they are factory 1.91/1.60 mid seventies heads. As long as you don't overheat the light castings you should be OK. I'm not going to push my 383 hard and I built it for low RPM torque, so the medium valves, 9.5 CR, mild hydraulic cam should work OK with the TH350 trans. I have about $3000 in the motor but I went with good quality for dependability and longevity. I agree with Partsman, a crate motor is easy and a good value.

Plus a GM crate engine comes w/ a warranty.

Got ya, turns out the car has 40690 original miles....found all the paperwork in the cubby hole behind the passenger seat. I think I might keep it original now :)

This will probably sound like a sales pitch. For about what you would have spent on yours,you could buy my 79 with most of the work already done! You get the "shark" look,and aren't hacking up a collector car. Decent power,super handling and the chance to make it look like your dream!
Check out the "For sale" forum.

Partsman your right on the money.

rm1sner if your not to concerned with parts matching and want more power that is your best bet. Those original Corvette ''power plants'' from the late 70s did not do the Corvettte justice anyways.
With the more cost effective price and performance of after market heads on the market today you may want to try a set. Although be aware you may blow out your rings on a high mileage engine;path of least resistence always prevails.

It seems you just got this C3 and feel you shouldn't have. You'r ready to unload it as quick as possible. Your other post indicates that. Slow down and asess what you have and the cost to get it right. I wouldn't be concerned about horsepower on paper. How does it feel while driving? Can cosmetics be added cost effectively? Then would you consider keeping it? It sounds like it was an impulse buy. Well you'v learned from it, now is selling for profit your goal? You will find yourself doing cosmetics to up it's appeal so that you can ask more than you paid or at least break even. If not, you should expect to leave ownership around where you entered $ wise.

Actually I've been doing this for a while trading, selling and buying...and it's perfect mechanically just stock though. It's basically a profit thing for me now, have a couple people looking at it for 7500

I can relate, I to have been trading. My C3 came in at 6K and if I put another $500 in it, I expect to loose it at about 7.5K. Good luck with yours.;)