advance curve kit
Thread Starter
Instructor
Joined: Feb 2004
Posts: 241
Likes: 0
From: Ravenna Ohio
advance curve kit
i got a advance curve kit and i read how you guys say all in at 2500 but according to the chartit just continues to get more advance as the rpm's continue. I was going to put in the lightest springs and the say 14* @ 2500 but it continues to advance to 24* @ 5000. So if I am aiming for 32* total then at what RPM do i check total advance. Am i overcomplicating this?
Josh
Josh
Racer
Joined: Jun 2004
Posts: 322
Likes: 0
From: The Dirty, Dirty South
To get total advance rev up until the advance tops out or you hit redline, you should top out before redline. If you put in the softest springs, you defintely will top out before redline. Now you can use the springs to tailor when total advance comes in. You will probably end up with 14 to 16 degress initial, and you want 36 degrees total by 2500-2800 rpm. Just set the total, and let the initial fall where it falls. If you get any pinging, back off in 2 degree increments until it goes away. I got my best results on a 350 with one silver and one black spring and 16 degrees intital after setting total at 36 at 2800 rpm.
Tech Contributor
Joined: Aug 1999
Posts: 14,377
Likes: 6,376
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by JDRez42
iAm i overcomplicating this?
Install the lightest springs. Disconnect your vacuum advance (just yank the hose off it) and set your total timing to 36 degrees by rev'ing the engine until the centrifugal advance does not go any further. This is your total advance setting. Note the rpm at which the centrifugal advance does not go any further: this is the "@ rpm" number. You want this to be no more than 2800. Then, drop the rpm down to a slow idle and check what your initial timing is (still with vacuum disconnected). You should have about 18 degrees. If so, hook up your vacuum advance to manifold vacuum and see how much additional timing it pulls in. It should be about 16 degrees more. If it's any more than 16, change the vacuum advance control unit. Contact me or post if you need more info.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
it really is that simple....i fiddled and farted around with different springs/settings/testdrives etc... and I made really good notes...I learned alot but in the end it was as simple as putting in the lightest springs and setting the timing like Lars said. Had i done this first, the whole process would have taken about 10 minutes....
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Also check to make sure your mechanical advance system is moving freely. Mine was totally jammed up, and even after some work it was tighter than it should have been...
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
Drifting
Joined: Sep 2004
Posts: 1,532
Likes: 4
From: Fairview Heights Illinois, near Saint Louis MO, STL C3 Shark
so, if I read this right:
1) check to make sure you're centrifugal advance isn't locked up, with gunk etc. if it is take care of that first
2) forget the rest of the springs, go for the lightest set first,
3) time to get about 36* at 2800rpms (point where it doesn't continue to advance)
4) re-connect vacuum, if greater than 16* additional advance, change the vacuum advance
I plan on doing this setup. I finally found someone that already has an adjustable timing light (just bought my non-adjustable one b4 reading all of these
) My 76 is not running to it's potential IMHO, and figure setting the timing right will have huge benefits. Have inlaws coming this next weekend but then I'll tear into it.
1) check to make sure you're centrifugal advance isn't locked up, with gunk etc. if it is take care of that first
2) forget the rest of the springs, go for the lightest set first,
3) time to get about 36* at 2800rpms (point where it doesn't continue to advance)
4) re-connect vacuum, if greater than 16* additional advance, change the vacuum advance
I plan on doing this setup. I finally found someone that already has an adjustable timing light (just bought my non-adjustable one b4 reading all of these
) My 76 is not running to it's potential IMHO, and figure setting the timing right will have huge benefits. Have inlaws coming this next weekend but then I'll tear into it.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by ruby76
so, if I read this right:
1) check to make sure you're centrifugal advance isn't locked up, with gunk etc. if it is take care of that first
2) forget the rest of the springs, go for the lightest set first,
3) time to get about 36* at 2800rpms (point where it doesn't continue to advance)
4) re-connect vacuum, if greater than 16* additional advance, change the vacuum advance
.
1) check to make sure you're centrifugal advance isn't locked up, with gunk etc. if it is take care of that first
2) forget the rest of the springs, go for the lightest set first,
3) time to get about 36* at 2800rpms (point where it doesn't continue to advance)
4) re-connect vacuum, if greater than 16* additional advance, change the vacuum advance
.
2. yes
3. yes
4......see what base idle timing setting is....then connect vacuum cannister to direct vacuum and see what final base idle timing is....the difference between the two is the vacuum advance.... good luck take good notes....i recorded the rpm for every 2* increase from base idle all the way to 36* and then again at 3K and 3.5K rpm. this represents your advance curve...
this is what mine looks like:
....using the two lightest springs I finally got it...20*/850, 22/1200, 24/1450,26/1600, 28/1700, 30/1800, 32/1900, 34/2300, 36/2500, 38*/3000 and it tops out there...so with vac can connected which is set at 13* i have 33*/1100 and the car runs incredibly strong......thks bob
Last edited by bobs77vet; May 9, 2005 at 02:45 PM.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by kodaclr
This might sound like a dumb question but If yoor doing this by yourself how do you know your RPMs when your holding the timing light and checking the timing?
make a jumper to put to the tach spade terminal onthe distributor (HEI) an hook up a tachometer
[IMG]
[/IMG] [IMG]
[/IMG]
Racer
Joined: Jan 2005
Posts: 492
Likes: 0
From: Birmingham AL
Originally Posted by bobs77vet
make a jumper to put to the tach spade terminal onthe distributor (HEI) an hook up a tachometer
[IMG][/IMG]
[IMG][/IMG]
[IMG]
[/IMG] [IMG]
[/IMG]
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by steves_77vette
Is that a voltmeter you're using as the tach? If so, what is the calibration table between voltage and rpm?
no its an old RAC tune up meter circa 1975...my first...man that makes me sound old
Racer
Joined: Feb 2005
Posts: 258
Likes: 2
From: Boise ID
I'm pretty sure that's a diagnostic tach. I've been trying to find one of those for a reasonable price (read: really cheap) for a while now with no success.
I've thought about a cheaper in dash tach that I could hook up and watch in the compartment, but in the end I got impatient and had my wife read the tach while I watched timing. (Unfortunately, i've no idea how accurate my tach is inside the car).
Dan
I've thought about a cheaper in dash tach that I could hook up and watch in the compartment, but in the end I got impatient and had my wife read the tach while I watched timing. (Unfortunately, i've no idea how accurate my tach is inside the car).
Dan
Thread Starter
Instructor
Joined: Feb 2004
Posts: 241
Likes: 0
From: Ravenna Ohio
I will do that but first i have to rebuild the carb it has been sitting fopr about 3 years so i think i should probably do it.. Anyway after breaking in the cam and a couple short trips down the road i took out the plugs and the are already pretty sooty(black). It is a stock holley 4160 i don't know what jets but i think they need switched. My bro said his plugs always looked like that since he started running the carb. ANy ideas on what jetting i should go with?
72h primary jets
72h primary jets
Last edited by JDRez42; May 9, 2005 at 07:38 PM.
Burning Brakes
Joined: Aug 2001
Posts: 1,160
Likes: 3
From: Greensboro NC
On my dist I need to have an initial of 25 to get 36 in by 2800 that means my mechanical is only adding about 11 degrees is that right? I'm using a pertronix unit and an adjustable timing light.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by micks69
On my dist I need to have an initial of 25 to get 36 in by 2800 that means my mechanical is only adding about 11 degrees is that right? I'm using a pertronix unit and an adjustable timing light.
probably means your springs are not opening all the way to let the advance in....try lighter springs.