Timing Question?
Thread Starter
Racer
Joined: Jun 2001
Posts: 289
Likes: 0
From: Duluth GA
Timing Question?
How does one determine the proper amount of timing advance to maximize performance. I am breaking my engine after a recent rebuild with some performance upgrades. The engine seems much stronger than before but it
it seems to be weak above 2500 rpm's. The timing was initially set at plus 4
because that is what the mechanic said that the book called for. The engine has not been tuned yet, but when I have the first oil change at 500 miles they
can optimize the timing and adjust the carburetor. :confused:
it seems to be weak above 2500 rpm's. The timing was initially set at plus 4
because that is what the mechanic said that the book called for. The engine has not been tuned yet, but when I have the first oil change at 500 miles they
can optimize the timing and adjust the carburetor. :confused:
Drifting
Joined: Jul 2001
Posts: 1,418
Likes: 1
Re: Timing Question? (Pat 69BigBlock)
Pat you post sit for a day w/o replies so I'll try to explain.I get some off the members confused as to who runs what but I think I remember you wanting to stay with stock distributor?Well that's besides the point.
Would be best to invest in a timing light for your own use to play and get it set to your liking instead of taking it back and forth plus mechanic hotrodding your car.
I guess you harmonic balancer is stock and not degreed in increments up to 50 or degrees.So get the timing light that has the dial to check total advance with the motor running at 2500 rpm.Should be about 36-38 total BTDC.Set initial at 12 and see how it cranks when hot.If it cranks hard,back it off 2 degrees at a time until it cranks properly.Eventually you might need to change the advance springs/weights but this should pep it up for starters.
This is not all there is to it,just a start.
Would be best to invest in a timing light for your own use to play and get it set to your liking instead of taking it back and forth plus mechanic hotrodding your car.
I guess you harmonic balancer is stock and not degreed in increments up to 50 or degrees.So get the timing light that has the dial to check total advance with the motor running at 2500 rpm.Should be about 36-38 total BTDC.Set initial at 12 and see how it cranks when hot.If it cranks hard,back it off 2 degrees at a time until it cranks properly.Eventually you might need to change the advance springs/weights but this should pep it up for starters.
This is not all there is to it,just a start.
C6 the C5 of tomorrow
Joined: Nov 2000
Posts: 6,665
Likes: 2
From: Twin Cities Minnesota
Re: Timing Question? (mountainmotor)
The best way to optimise the timing is at the drag strip.
Most engines run best with 34-38 degrees of total timing. This is usually by about 3000rpm and should be measured with the vac advance disconnected since at WOT it is basically not there..
Get a 'Timing tape' it sticks to your harmonic balancer so you can see the actual timing no matter what it is.
Run the engine and watch the timing advance and the rpm. Note the RPM when the timing no longer advances and the actual advance.
( sometimes factory distributors never fully advance and some times they stick untill the engine is rev'ed, both bad, the advance curve should be smooth and should stop before the redline )
Adjust your timing at idle to make the total advance about 36 degrees.
Make a couple of runs down the drag strip trying to be completely consistant and note the speed and ET. Repeat at 34 and 38 degrees. Then, keep changing the timing until it's as good as it gets...
Most engines run best with 34-38 degrees of total timing. This is usually by about 3000rpm and should be measured with the vac advance disconnected since at WOT it is basically not there..
Get a 'Timing tape' it sticks to your harmonic balancer so you can see the actual timing no matter what it is.
Run the engine and watch the timing advance and the rpm. Note the RPM when the timing no longer advances and the actual advance.
( sometimes factory distributors never fully advance and some times they stick untill the engine is rev'ed, both bad, the advance curve should be smooth and should stop before the redline )
Adjust your timing at idle to make the total advance about 36 degrees.
Make a couple of runs down the drag strip trying to be completely consistant and note the speed and ET. Repeat at 34 and 38 degrees. Then, keep changing the timing until it's as good as it gets...
Heel & Toe
Joined: Dec 2001
Posts: 21
Likes: 0
From: Easthampton MA
Re: Timing Question? (Pat 69BigBlock)
There are some pretty good instructions right here in the C3 Tech Tip section. Lars is very well regarded so I wouldn't hesitate a bit to try his technique.
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Re: Timing Question? (427V8)
The best way to optimise the timing is at the drag strip.
.
.
Oh, and definitely find the paper Lars wrote, titled almost exactly as your question: "Setting timing for maximum performance" or something like that... MJ
Here, I found it for you: titled:
How to Set Your Timing for Peak Performance
Go to http://www.corvettefaq.com
click on, engine/drivetrain
in alphabetical order, you want: How to Set Timing White Paper
by Lars Grmsrud
enjoy! MJ
[Modified by MNJack, 9:50 PM 2/13/2002]
Pro
Joined: Jan 2002
Posts: 534
Likes: 0
From: FL
Re: Timing Question? (Pat 69BigBlock)
Advance it until the engine *just* blows apart from detonation, then back it off 3 degrees. :jester
Sorry, couldn't resist a variation on the old "How much do I torque this bolt? Torque it 'til it breaks, then back off 15 foot-pounds." joke. :D
-Noel
Sorry, couldn't resist a variation on the old "How much do I torque this bolt? Torque it 'til it breaks, then back off 15 foot-pounds." joke. :D
-Noel
