Valve Adjustment

[Todd L.]

Looking for information on adjusting my valves on a 74 BB. When I shut the car off a flame shoots out of the carb. I was told that either my intake valves are not closing or the timing is off. Any one know of a website or book I could read to learn?

Thanks

Todd

[Michael W.]

Re: Valve Adjustment

If your engine is stock, you have hydraulic lifters. A search of the archives here will give you lots of references on how to adjust them as will the GM service manuals.

[Joe L.]

Re: Valve Adjustment

Looking for information on adjusting my valves on a 74 BB. When I shut the car off a flame shoots out of the carb. I was told that either my intake valves are not closing or the timing is off. Any one know of a website or book I could read to learn?

Thanks

Todd

Todd-----


How does the car run otherwise? If either of the conditions you mentioned were as far "out of whack" as it would take to cause serious back-fire through the carburetor, I would expect the car to run in a VERY unsatisfactory manner.

[Todd L.]

Re: Valve Adjustment

All I can say is the car runs, when I bought it, it ran rough and would not stay running. I found three intake valves stuck. I had to replace the three push rods, so I removed the rockers. I did not know how to adjust the rockers so this may be a problem, I do not know if the carb needs adjusted, the plugs I know are new and gapped properly, the wires I could replace if it would help, and everything else is a mystery. I would just like to get to a base line. And start working form there. I plan on doing a full restoration, but until then I just want to make the car driveable. Any help would be appreciated, Where can I get the service manual?

[Louis T.]

Re: Valve Adjustment

Hi Todd,

For a repair manual, start by clicking on the NCRS Store link at the top of your page, then click on the C3 Library link. For starters, pick up the 66-82 Corvette Shop Manual - that's what you'll need for your valve and carburetor adjustments. Thinking about what your initial library should also include, you should also pick up the 1974 Corvette Factory Assembly Instruction Manual, 1974 Chassis Service Manual (this is currently out-of-print but you can find used copies on eBay and other places on the internet), 1973-77 Operations & Performance Verification Guide, and don't forget the 73-74 Technical Information Manual & Judging Guide (even if you're nowhere near getting your car judged, it contains a wealth of information that will also help you ascertain if visible components have been modified from their original configuration).

And don’t forget to search the TDB archives - there is an incredible amount of information about the theory and operation of all of the components of your car, and don’t only limit your searches to your model year and engine, as many concepts and techniques span many model years and engines.

Best of luck!

Louis

[James H.]

Re: Valve Adjustment

Todd............This may sound simple but check your firing order before pulling your valve covers.

Good Luck,

Jim

[Jim T.]

Re: Valve Adjustment

Todd the 1974 Shop/Service Manual is out of print at the NCRS Store, however www.helminc.com still shows that it is available. Helm is who you would of bought it from in 1974 from information in your owners manual.

[Joe C.]

Re: Valve Adjustment

All I can say is the car runs, when I bought it, it ran rough and would not stay running. I found three intake valves stuck. I had to replace the three push rods, so I removed the rockers. I did not know how to adjust the rockers so this may be a problem, I do not know if the carb needs adjusted, the plugs I know are new and gapped properly, the wires I could replace if it would help, and everything else is a mystery. I would just like to get to a base line. And start working form there. I plan on doing a full restoration, but until then I just want to make the car driveable. Any help would be appreciated, Where can I get the service manual?

Very likely.......there is an intake valve remaining open! Start by readjusting the three lifters that belong to the pushrods you replaced. On a warm engine, rotate engine until each lifter to be adjusted has its valve fully closed. Back off adjusting nut until rocker has play. Tighten nut until rocker has no play, then, tighten an additional 1/4 turn.
Here is a good explanation of tappet adjusting procedure:

http://www.centuryperformance.com/adjusting-valve-lash-spg-149.html

[Todd L.]

Re: Valve Adjustment

Thanks guys I am ordering some books now. I do own the AIM and the Judging Guide. I did take a look at the wiring I do not know how the distribution works but my wiring does not seem correct. This is what I traced on the distributor cap:

The plug that is the furthest forward connects to the front left plug, I believe is the # one cylinder.
In a clockwise direction
1, 8, 4, 3, 6, 5, 7, 2

Correct me if I'm wrong, the left side of the engine (drivers side) is the 1, 3, 5, 7 cylinder; one is the furthest forward.
On the right is 2, 4, 6, and 8 with 2 being the furthest forward.

[Joe L.]

Re: Valve Adjustment

Thanks guys I am ordering some books now. I do own the AIM and the Judging Guide. I did take a look at the wiring I do not know how the distribution works but my wiring does not seem correct. This is what I traced on the distributor cap:

The plug that is the furthest forward connects to the front left plug, I believe is the # one cylinder.
In a clockwise direction
1, 8, 4, 3, 6, 5, 7, 2

Correct me if I'm wrong, the left side of the engine (drivers side) is the 1, 3, 5, 7 cylinder; one is the furthest forward.
On the right is 2, 4, 6, and 8 with 2 being the furthest forward.

Todd-----


You have the firing order correct (it should also be embossed on your intake manifold) and you have the cylinder numbers correct as to number and bank.

The #1 cylinder should be on the distributor cap tower that is on the LEFT side of the window (as you look DOWNWARD on it) and then proceeds CLOCKWISE (as you look downward on it) according to the firing order.

[Joe C.]

Re: Valve Adjustment

Thanks guys I am ordering some books now. I do own the AIM and the Judging Guide. I did take a look at the wiring I do not know how the distribution works but my wiring does not seem correct. This is what I traced on the distributor cap:

The plug that is the furthest forward connects to the front left plug, I believe is the # one cylinder.
In a clockwise direction
1, 8, 4, 3, 6, 5, 7, 2

Correct me if I'm wrong, the left side of the engine (drivers side) is the 1, 3, 5, 7 cylinder; one is the furthest forward.
On the right is 2, 4, 6, and 8 with 2 being the furthest forward.

All correct...............like I said, check the lash on the 3 valves you fooled with!