Timing curve Question, Help needed.
Thread Starter
Instructor
Joined: Dec 2007
Posts: 245
Likes: 2
From: Jersey shore NJ
Timing curve Question, Help needed.
Hi guys, I trying to get my timing set before adjusting my new carb.
I have already read Lar's and Barryk's papers on timing and think I understand them.
here are my queations,
I'm only getting 16 degrees of centrifical advance. This means that I need to have my Initial timing set to 20 degrees to get the full 36. Does this seem high for Initial ? Should I be getting more out of the centifical?
Also the centifical advance starts coming in right off idle and All in at 1500rpm. ( I assume I need to change my springs so it comes in a little later, right? )
Thanks for any replies!
I have already read Lar's and Barryk's papers on timing and think I understand them.
here are my queations,
I'm only getting 16 degrees of centrifical advance. This means that I need to have my Initial timing set to 20 degrees to get the full 36. Does this seem high for Initial ? Should I be getting more out of the centifical?
Also the centifical advance starts coming in right off idle and All in at 1500rpm. ( I assume I need to change my springs so it comes in a little later, right? )
Thanks for any replies!
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
That does seem a little strange if it is a stock dist. Most of them have about 20 degrees centrifical and they don't come all in until about 4000 rpm. Very heavy springs. You want it all in by about 2500 rpm. The 20 initial seems a little much but what cam are you running and what is therest of the setup.
Le Mans Master
Joined: Aug 2006
Posts: 7,411
Likes: 1,551
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
As stated, you should get 20* to 24* of centrifugal advance. If your only getting 16* than the stop bushing might be to big or a PO filled in the slot. If your advance is coming all in at 1500 RPM than you need stronger springs. PG.
Thread Starter
Instructor
Joined: Dec 2007
Posts: 245
Likes: 2
From: Jersey shore NJ
This is the stock HEI. And as far as I know the stock springs. Maybe the springs are stopping the advance at 16 degrees? I will look at the weights again to see if they are haning up or if something was modified.
Pro
Joined: Feb 2007
Posts: 548
Likes: 1
From: Victoria VA
I had some problems with my 77 I took and cleaned everything up really good and then I got a curve kit and ended up only using 1 silver spring to get my timing where I wanted it. I also got a new vac advance can that was adjustable. I started out with no vac advance the can was bad and the centifical was semi rusted and gummed up and with my timing set at 18 degrees the centifical was only giving me 36 degrees but it was not until 4500 rpms. Check out this link to what I did and all the help I got.
http://forums.corvetteforum.com/c3-t...ease-read.html
http://forums.corvetteforum.com/c3-t...ease-read.html
Instructor
Joined: Jan 2007
Posts: 231
Likes: 41
From: Simpsonville SC
My 78 L-82 stock distributor only had 16* mech. advance.
Dist.# 1103291 --vac.can is 10*@ 8"vacuum --mech.adv. is 16*@ 2000rpm
I never felt I could get enough timing out of it. But now that I'm running Vortec heads, it's perfect. Vortec heads like less total timing 28-32* 14-16* initial and 16*mech.
Dist.# 1103291 --vac.can is 10*@ 8"vacuum --mech.adv. is 16*@ 2000rpm
I never felt I could get enough timing out of it. But now that I'm running Vortec heads, it's perfect. Vortec heads like less total timing 28-32* 14-16* initial and 16*mech.
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Racer
Joined: Jan 2007
Posts: 314
Likes: 0
From: Pittsfield, Ohio
Great thread. Now I want to go out and check my 76. I think when I did mine initial was set at 12 degrees as I did what the decal in the engine compt. said. Bet thats why its hard to start and seems sluggish..
