Ignition Timing

[Stallion]

I have a '78 SA Corvette, and I'm trying to time the engine right now. I'm supposed to disconnect the vacuum advance, right? And then set the idle to 700 RPM? Or the other way around? The revolutions drop significantly after the vacuum advance is disconnected, and I'm just looking to clarify whether to set the RPM (to 700) before or after the vacuum advance is disconnected. And then time the engine at 700 RPM?

It's 6 to 8 degrees advance, I believe. Does it matter if the carburetor is a '79 California carb?

Thanks in advance!

 

[spikebot 81]

There is a bunch of how too's on timing a sbc, but you should have the idle set first and then disconnect the vac advance. Set the timing reconnect the vacuum advance and rest the idle. Here is a good read on timing

Info on Timing - long post! - Corvette Forum

and another

http://www.corvetteactioncenter.com...ion-timing-what-i-want-what-engine-wants.html

 

[Stallion]

Thanks for that. What exactly does the stock sticker say? Unfortunately it's not intact right now. What's the stock advance on this Corvette? 6? 7? 8 degrees?

Thanks in advance.

 

[JohnZ]

Thanks for that. What exactly does the stock sticker say? Unfortunately it's not intact right now. What's the stock advance on this Corvette? 6? 7? 8 degrees?

Thanks in advance.

There should be a chart in your owner's manual that shows the timing specs; if not, it's in the Shop Manual.

 

[mike82]

do you have L82 or L48?

 

[Stallion]

It's an L48. I'm sure it's in the shop manual, I'm just trying to troubleshoot this problem from 400 miles away. Any help on how many degrees for stock advance would be much appreciated.

 

[mike82]

a friend of mine has a 78 SA L48 auto. his decal reads 6*.

 

[Hib Halverson]

As "mike82" states above, the timing is 6° BTDC.

You set the idle speed with the vac. adv. connected. Then, unplug the vac. adv. plug the hose then set the timing at 6 degrees.

Reconnect the vac. adv. then readjust the idle speed.

 

[cleon]

You may want to check your balancer on the front of the crankshaft.
I found that the one on my 1979 had turned, TDC was not correct.
The key way is about 4 deg. retarded. My balancer TDC was about 16 deg advanced I was unable to set timing until I replaced the balancer.