Hi all, i recently bought a 1980 corvette which i had been searching for a while. My goal was to buy a black on black 4 speed car which was the same car i took my wife to our high school prom way back in 1983. I found one that was in fantastic condition cosmetically, but need some feedback on the motor condition.

Smoking from the exhaust when?All the time? Only on acceleration? Only on deceleration?

#7 looks to have some oil fouling/carbon build-up. #s 3-5-2-6 look fairly reasonable for some mileage. #s 4 & 8 are really lean.

Compression readings don't look all that bad to me. What is the mileage on the car? When checking compression, did you have all of the plugs out, and the throttle held wide open?
The later engines like yours dint have a lot of compression to begin with, compared to the engines of the early '70s.
I'd venture a guess and say you have more of a carb/ignition issue that a worn engine problem. Also possible the intake is leaking, causing the lean condition on the two cylinders, and oil fouling on others. 600 double pumper is really too much carb for a smog engine, imho.
 Need a little more diagnostics to determine just what is going on. Put the new plugs in and see what happens.

Don't know where you live, but if you can get some RXP, run a couple of tanks treated with it to see if you can burn off some of that carbon.

Don't Holley's run kinda rich?  I know mine does, but it has bigger jets for the ethanol in the gas.  Has to run richer.

http://www.rxp.com/

Thanks Joel, the smoking seems to be mostly on startup. After it's warmed up i dont really see any in the exhaust. As for miles, it's currently at 105, 000. and for the compression that's what i wasnt sure about being a 1980 block and heads which as i'm learning are low compression. I'm also reading that a cam/head swap will do wonders for the L48. I did install a fresh set of Accel shorty plugs while i had them out so i'll run it for a bit and see what they look like as well as the oil level.

F4Gary, i'm on the opposite side of the Metroplex from you. Northeast area just into Hunt county. I'll stop in at the local Oreilly and get some.

|UPDATED|9/22/2015 7:18:29 AM (AZT)|/UPDATED|

Smoke mostly at startup is usually valve seals. Oil runs down the valve stem when parked, into the intake/exhaust ports, then into the engine on startup, causing the smokey start. Valve guide wear will do it, too, but installing new guide seals is much easier than pulling the heads for guide repair.

The only real way to wake up a low compression engine is to raise the compression ratio. Changing to a bigger cam will hurt more than help, because there's just not enough compression to take advantage of the cam. Different heads can raise the compression ratio some, but not much. Flat top pistons, or even domed pistons will do the most good, compression-wise. You really need around a 9.5:1-10:1 ratio to make one really shine. Changing the heads alone won't do that....but it would help.

Thanks Joel, great info !

yes  replace valve seals.  my 79 lets out a litte blue when started  has 92000 miles like a lot of old timers I like to see a litte smoke just seems right but if my 07 does ,now we take a look for a problem, ilke litte smoke makes engine be alive not some new super car,just me everthing I have is older than 20 years.     injoy it   you may never see again. dwa

I agree with DWA. I had similar fouling on a few of my plugs. I haven't replaced the valve seals yet but will this fall. I did a compression check on my 77 L48 and my readings were in the 135 to 150 range. I believe it is stock but I know that it has been rebuild by someone before me.