Timing Adjustment
Thread Starter
Instructor
Joined: Apr 2004
Posts: 221
Likes: 24
From: HOMOSASSA FL
Timing Adjustment
Good morning everyone. Can some help me with the proper timing adjustment for my 1970 350/300hp auto. The Corvette is stock with a original Rochester Quad. Due to the quality of fuel they produce today I would like to make sure that a stock timing setup is proper "Initial and Advanced". The fuel I'm running in the Corvette is Shell 93 oct. The TCS is functional on the Vehicle. I know that some Corvette Drivers disconnect this device. Does it help to do so and if so is there a procedure for disabling the TCS. Thanks Droop
Instructor
Joined: May 2005
Posts: 200
Likes: 4
From: Richmond Virginia
This is the paper I've seen recommended before that I've used myself. I need to do this again, since I adjusted a couple things I haven't tuned it again.
http://www.corvette-restoration.com/...ine_Timing.pdf
http://www.corvette-restoration.com/...ine_Timing.pdf
Race Director
Joined: May 2006
Posts: 18,692
Likes: 2,572
If you don't want to modify the advance curve just set it for initial stock number after setting the dwell. Then run a vacuum line from any port that has vacuum at idle to the distributor thus eliminating the TCS.
Last edited by MelWff; Nov 10, 2015 at 03:21 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The intent of the TCS system is to retard the spark timing so that the engine will run hotter and burn more hydrocarbons.
This does not help the car run better; it will make idle more erratic and performance will be reduced.
You can leave all the TCS stuff on the intake manifold; just disconnect/plug the necessary vacuum lines and install a direct line from the dist. advance can to a manifold vacuum fitting on your Q-Jet (usually the tube that sticks out from the choke mechanism on the right side). This will give you better idle quality and performance. But, when you want to have the TCS system hooked up for a car show...or because you need to pass an emission inspection, swap connections so that the TCS is functional again.
When running on manifold vacuum, you can change your timing at idle to about 12-14 degrees advance. That will give you somewhat better performance without having to recurve your distributor. Or, you can go through the process of changing springs in the mechanical advance system in the distributor, if you want to optimize performance.
This does not help the car run better; it will make idle more erratic and performance will be reduced.
You can leave all the TCS stuff on the intake manifold; just disconnect/plug the necessary vacuum lines and install a direct line from the dist. advance can to a manifold vacuum fitting on your Q-Jet (usually the tube that sticks out from the choke mechanism on the right side). This will give you better idle quality and performance. But, when you want to have the TCS system hooked up for a car show...or because you need to pass an emission inspection, swap connections so that the TCS is functional again.
When running on manifold vacuum, you can change your timing at idle to about 12-14 degrees advance. That will give you somewhat better performance without having to recurve your distributor. Or, you can go through the process of changing springs in the mechanical advance system in the distributor, if you want to optimize performance.
Last edited by 7T1vette; Nov 11, 2015 at 01:10 PM.
Melting Slicks
Joined: Apr 2009
Posts: 2,632
Likes: 112
From: Great Plains Iowa
Good morning everyone. Can some help me with the proper timing adjustment for my 1970 350/300hp auto. The Corvette is stock with a original Rochester Quad. Due to the quality of fuel they produce today I would like to make sure that a stock timing setup is proper "Initial and Advanced". The fuel I'm running in the Corvette is Shell 93 oct. The TCS is functional on the Vehicle. I know that some Corvette Drivers disconnect this device. Does it help to do so and if so is there a procedure for disabling the TCS. Thanks Droop
First of all the low compression 300 hp engine only needs 87 octane so the 93 octane that you are buying is just a waste of money. Time it to 6 degrees and close the hood..................
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,116
From: Crossville TN
The idle setting for timing that General Motors specified had little to do with what was 'best' for the engine, the vehicle, or the owner. It was only 'best' for GM! Retarding timing reduced warranty....simple as that.
So, if you want your car to be the slug that GM wanted you to get, by all means, GO FOR IT! Otherwise, you can advance the timing a few degrees (not really into the realm of 'uncharted territory') and wake up the engine a bit, smooth out the idle a bit, probably reduce fuel usage at idle, and run the engine a bit cooler at idle, too.
As always, it's your car and you can do with it what you desire.
So, if you want your car to be the slug that GM wanted you to get, by all means, GO FOR IT! Otherwise, you can advance the timing a few degrees (not really into the realm of 'uncharted territory') and wake up the engine a bit, smooth out the idle a bit, probably reduce fuel usage at idle, and run the engine a bit cooler at idle, too.
As always, it's your car and you can do with it what you desire.
