timing conundrum
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 977
Likes: 1
From: wash. dc
timing conundrum
i've been following bob77 vet ordeal with his timing issues...here are mine; i have a 71 LS5 thats all stock. last weekend i did the lars way of tuning carb and setting timing for max performance... at 8* initial timing at 600 rpm vac disconnected, i get 15 in. of vac... at 2500rpm i get 38* advance timing with springs out of distributor...yet when road testing i still get hesitation at wot and much popping at deceleration... where do i go from here, i put newly rebuilt carb on last summer when i bought it but it hasn't solved my bad running condition. i admit its better but not right. i also installed an undercar chambered exhaust this winter. the sound is awesome...help
Safety Car
Joined: Jun 2004
Posts: 4,652
Likes: 80
From: Lakeland Florida
Hello,
First of all, can you explain your comments of " with springs out of distributor"?
does that mean you are not using any advance springs at all? In that case, the cams/advance weights should always be at max position.
kdf
First of all, can you explain your comments of " with springs out of distributor"?
does that mean you are not using any advance springs at all? In that case, the cams/advance weights should always be at max position.
kdf
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
ok follow me so that we have the blind leading the blind.....isn't 8* initial timing way low? you say you get 15" of vacuum at idle thats good so you would think your vacuum advance would come in, have you checked this to verify that the vac cannister is working and actually advancing your timing? you took the dist springs out so you know that you have a centrifugal advance but then you presumably put them back in right? so what is your timing at 2500-3000 rpm with the springs in there? are you running ported or direct vacuum and have you played with this to see if your car runs better.
heres the magical numbers that we are looking for 16-18* initial timing, 36* total timing (with vac can disconnected all in by 2500-3000) and a 16* vacuum advance. sounds esy enough right...good luck and keep us posted, after i finish my exhaust i'm going back to my timing and wrapping it up once and for all.
heres the magical numbers that we are looking for 16-18* initial timing, 36* total timing (with vac can disconnected all in by 2500-3000) and a 16* vacuum advance. sounds esy enough right...good luck and keep us posted, after i finish my exhaust i'm going back to my timing and wrapping it up once and for all.
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 977
Likes: 1
From: wash. dc
timing
, i'll have to write all these numbers down when i check it out again but trying to go from memory. initial timing for my year is supposed to be 8* at 600 rpm... my timing gauge on my balancer only goes up to 12... when i give it gas with the springs out or in the vac does increase though i can't recall to what number... when i reinstall springs i still get 36* at 2500 rpm and i'm running port vac... don't really know how to get manifold vac, so my timing seems to be on the money but at wot still the hesitation....i'll go out this weekend when the weather allows and go through everything again.... thanks for the help
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 977
Likes: 1
From: wash. dc
timing conundrum
update; got my paper out on lars timing for optimal performance... with advavce springs out and vac disconnected had no prblem getting 36* advance timing at 2500 rpm... however, when i reinstalled the springs and revved it up i didn't eveb see the timing mark... so my guess is i need to hunt down softer springs as centrifugal advance is not reaching the 36* mark... went to napa yesterday and asked for carb springs and the kid said; springs for a carb? huh...well they didn't have any...where the most likely place i might softer springs for the carb...
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 71redskin
... however, when i reinstalled the springs and revved it up i didn't eveb see the timing mark... so my guess is i need to hunt down softer springs as centrifugal advance is not reaching the 36* mark... ...
