you'll always be at the mercy of repair shops unless you get a few basic tools and some basic understanding of how each system on the car functions
a decent timing light won,t cost more than about $40-$50 and you can commonly buy them at yard sales for $10
adjusting valves is really simple once you understand the process, Id strongly suggest getting a timing light and a few basic tools and a CHEVY SHOP MANUAL FOR YOUR YEAR CORVETTE!READ THRU THESE LINKSviewtopic.php?f=70&t=1411viewtopic.php?f=52&t=196viewtopic.php?f=50&t=383viewtopic.php?f=50&t=821&p=1212#p1212http://www.helminc.com/helm/product2.as ... JCAQPL3BB5this also helpshttp://www.delmarlearning.com/browse_pr ... cat2ID=CHM
A rough idle is sometimes a result of a vacuum
There are typically tthree vacuum
sources (on earlier muscle car engines) that are in addition to the more common
intake and carb, sources that can cause a vacuum
leak, these are the vacuum
booster for the power brakes and the intake vacuum
line running down to the vacuum
modulator on the transmission, and in a few cases vacume lines running to fuel presure regulators that compensate for vacume readings.
You will need to have plugged each line individually to test each potential source, or vacuum
line, you should disconnect and plug the vacuum
modulator line, to the transmission, the power brake booster line, and on some later cars theres vacuum
lines connected to the emission controls or auto cruise controls and see if each change helps the idle.
modulator on a turbo -350 and turbo 400 style trans can start to leak both vacuum
and suck transmission fluid, up into the intake. If you have been losing trans fluid, or the exhaust smokes under high vacuum
readings it could be transmission fluid being sucked through a defective modulator up into the intake - this will DEFINITELY cause a rough running motor during idle, and smoke from the exhaust and spark plugs to be discolored on runners near the vacuum
line connection to the intake manifold.
naturally youll want to use the unlit propane torch, to locate intake leaks, on the carb or intake gasket, but remember that improperly machined head or a badly machined intake , or improperly installed intake gasket can suck oil from the lifter gallery
Don't anything is good or bad till its isolated and tested good or bad. never assume anything without testing.
reading will depend on the displacement, compression ratio and cam timing-