Setting up total timing
Thread Starter
Advanced
Joined: Apr 2005
Posts: 82
Likes: 0
Setting up total timing
I have install a Mallory distributor in my 81. Question is I have the base timing set at 12 and medium springs in dist. Looking at the timing mark at 2800 rpm I am reading 28 BTDC with a dial back light. The dist has adjustable vac can. Now to adjust my total timing where do I start? Do I keep the dist in the same place and change springs? Will that make it go up higher. Or do I take the springs out start it up and run to 2800 rpm and see where the mark goes and then change the springs to get my total timing? Confused....
Pro
Joined: Jun 2005
Posts: 660
Likes: 4
From: Fredericksburg VA
The springs are there to mainly help regulate the speed (degrees advance per RPM) the timing advances. Keep the distributor where it is adjust the vacuum can and springs to get what you want. You may need to set total advance and then turn the distributor to get some more if you need it. You don’t want to go too much with the moving the distributor because it also adjusts your initial timing. The 28 that you have don’t sound to bad though depending on what other eng components you have. Revving the car in the driveway doesn’t do much with setting the vacuum can. You need to drive the car. Don’t send me the ticket if you are not careful. Do the drive testing on a deserted road no children, pets, etc.
Racer
Joined: Dec 2003
Posts: 304
Likes: 0
From: Pasadena Maryland
As I understand it. Total timing is the initial timing + the centrifugal advance added together. The heavy springs allow the timing curve to come in slower than lighter springs. I run my total advance around 32 to 34 degrees. Some like to go higher. The rule of thumb is to run as much timing as you can. If you hear pinging at wide open throttle retard the timing a little until it stops. Make sure your vacuum advance is plugged off when you set your timing. I'm sure someone will chime in and put their .02 worth in too. good luck
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
heres some info...read it all, i think i encountered every possible combination..... especially post 33 and 40
http://forums.corvetteforum.com/show....php?t=1059896
http://forums.corvetteforum.com/show....php?t=1059896
Last edited by bobs77vet; Jun 14, 2005 at 09:56 AM.
Drifting
Joined: Nov 2002
Posts: 1,665
Likes: 1
From: Ontario
I have light springs and heavy weights so my timing comes in fast, but my total mechanical advance just wasn't going far enough. I had to grind down the centre piece of the weights a bit in order to allow the weights to travel further, therefore increasing my total mechanical.
Ho to set your timing for peak performance by Lars
Good post bobs77vet!
Ho to set your timing for peak performance by Lars
Good post bobs77vet!
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
Put the lightest springs you have in there (if you don't have 'em, get some!) Disconnect vac advance. Set total timing for 36 degrees -- at whatever RPM it comes in at (doesn't matter for now). Then replace the lighter springs with progressively heavier springs until your total timing (ie., advances no more) comes in at 2800. Done.
I'll repeat this for the sake of emphasis: Total timing occurs with vac advance disconnected, and mechanical advance advancing to its highest point! Time the engine to 36 degrees at this point, and then use the springs to adjust the rpm at which it is reached. When you replace the springs to recurve the distributor you do not need to readjust timing.
I'll repeat this for the sake of emphasis: Total timing occurs with vac advance disconnected, and mechanical advance advancing to its highest point! Time the engine to 36 degrees at this point, and then use the springs to adjust the rpm at which it is reached. When you replace the springs to recurve the distributor you do not need to readjust timing.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Your initial timing should be around 14 to 16 BTDC. Not really important. The total timing is initial plus centrifical which should be at around 34 to 36. The total timing is more important than initial. You just want the initial timing set so the car idles fine and stays cool. Vaccum advance will help this. If you are not getting enough centrifical you have to check to see if anything is binding up or just have the dist. setup properly. Make sure it is all in by 2500 to 2800 rpm for best performance.
