Help, C3 won't pass inspection

[JohnZ]

The timing chain drives the cam from the crankshaft (the cam runs at 1/2-crank speed), and the relationship between the two never changes (unless the sprockets wear and the chain jumps a tooth). This ensures that the cam opens and closes the valves at the right point relative to where the pistons are as the crankshaft rotates. You can learn a lot more about how the internals of an engine relate to each other at www.howthingswork.com.

 

[page62]

The '78 did not have a computer. In '80 the Kalifornia Vettes got computers, followed by everyone else in '81.

Cam timing can only be changed by replacing the cam. Its job is to make the valves go up and down at the proper time, thus allowing fresh air into the cylinders and exhaust out at the appropriate times.

Ignition timing is adjusted by rotating the distributor assembly.

Don't worry, Stallion. You'll catch on to all of this!

 

[Stallion]

Okay, I see how it all comes together. Is it better (and more maintainable) to have this computer in your Vette? Or does it just make things harder?

 

[JohnZ]

Computerized engine controls and fuel injection have done wonders for fuel economy, driveability, low emissions, performance and reliability compared to the older non-computer carbureted cars, but have added enormous electrical complexity and cost, and have made it very difficult to work on the cars without specialized diagnostic equipment. Like anything else, it's a trade-off. I love the way my computerized daily drivers run, but for my "toys", I like to do my own work.

 

[Stallion]

I see what you mean, John. And I would think that's how I'm going to want it to. Go for a carburated engine, is what I'm thinking. Of course, in the generation of Vettes that I'm looking at, a majority are carbs. And that's good!

TR

 

[WhalePirot]

Cam timing can only be changed by replacing the cam.

Not entirely true. Cam timing can be changed with offset keys, used largely in overhead cam engines; essential if the heads are milled, to restore proper camshaft timing.

Improper installation of the timing chain components can mis-time the camshaft, but it is difficult screw up if one follows the simple procedure. i know of no factory engine that uses anything other than a timing chain or belt to turn the camshaft.

After market gear drives are available, but the is no advantage in 99% of street engines, and they can be very, very noisy!

The electronics do the same thing as the 'old' components, but more precisely. Fuel use is optimized, but the largest gain in economy has been the gearing and trend towards 'torquey' engines that pull 'down low'. The RPM at EPA test speeds are so low as to be amazing to older heads.

As the components change, so does the process and the test gear. Some mechanics have not made a full transition to these electronically managed engines, when it is actually not so difficult. The process has not changed, but reaching the components for testing and getting past all that plumbing is time consuming. The ECM is a great toubleshooting tool, but the basics still apply, such as vacuum leaks and failing spark delivery components.

John, great suggestion on the 'howthingswork' site.

"No dumb questions; only dumb answers."

Read, ask. listen, try and make mistakes, but learn!

 

[Vette/Berlina-coupe]

HelloRick(black'nblue95): -hummm, excellent suggestion about how to check for a loose Timing-chain (without having to unnecessarily tear things apart), --merely by disassembling the top of the distributor so as to actually observe the cam-driven distributor-shaft itself as you apply a longarm socket-wrench back-and-forth to the Crank-nut as to observe the amount of slack-lag (ideally "none" noticable) prevailing between the small/Crank-gear and the big/Cam-gear (1 : 2 -ratio)! Any of you Vetter'ens near Rick, should wisely see him for attention to your C3-problems (and other Vet models as well I imagine); --this guy is a sharp cookie (knows how to trouble-shoot without needless repairs); --unfortunately I am out here on the lower-end of the left-coast!
Also very much impressed by our resident-747(whale-Pilot) "Capt.Mike", -who exhibits a whole lot of moxie about what makes it all go-around in a reciprocating manner (although he's probably got a turbine-engine in his nifty Vette!)... -B.B.
:dance :s

 

[Stallion]

Say you had a mis-timed cam. What would happen when you would, say, start the ignition? Would it even start?

TR

 

[BlackNBlue95]

HelloRick(black'nblue95): -hummm, excellent suggestion about how to check for a loose Timing-chain (without having to unnecessarily tear things apart), --merely by disassembling the top of the distributor so as to actually observe the cam-driven distributor-shaft itself as you apply a longarm socket-wrench back-and-forth to the Crank-nut as to observe the amount of slack-lag (ideally "none" noticable) prevailing between the small/Crank-gear and the big/Cam-gear (1 : 2 -ratio)! Any of you Vetter'ens near Rick, should wisely see him for attention to your C3-problems (and other Vet models as well I imagine); --this guy is a sharp cookie (knows how to trouble-shoot without needless repairs); --unfortunately I am out here on the lower-end of the left-coast!
Also very much impressed by our resident-747(whale-Pilot) "Capt.Mike", -who exhibits a whole lot of moxie about what makes it all go-around in a reciprocating manner (although he's probably got a turbine-engine in his nifty Vette!)... -B.B.
:dance :s

Thank you very much for the compliments.. Yes if anyone needs any help or anything with any year corvette let me know..