Can timing be changed on LT4?
Thread Starter
Team Owner
Joined: Feb 2006
Posts: 23,124
Likes: 117
From: San Antonio Texas
Can timing be changed on LT4?
I know the timing is all in the Opti and the computer, but can it be changed by computer tricks on an LT4?
I just changed another Opti and although it runs just fine (better actually) the highway mileage seems a couple of mpg lower than it had been on previous long hauls. Not at all bad, just not quite as high as I've seen it in the past. I don't have a clue how to even check the baseline on this or how to advance timing if it is even possible. Is it?
(Computers
)
I just changed another Opti and although it runs just fine (better actually) the highway mileage seems a couple of mpg lower than it had been on previous long hauls. Not at all bad, just not quite as high as I've seen it in the past. I don't have a clue how to even check the baseline on this or how to advance timing if it is even possible. Is it?
(Computers
)
Pro
Joined: Aug 2009
Posts: 725
Likes: 4
From: Plano, TX
I know the timing is all in the Opti and the computer, but can it be changed by computer tricks on an LT4?
I just changed another Opti and although it runs just fine (better actually) the highway mileage seems a couple of mpg lower than it had been on previous long hauls. Not at all bad, just not quite as high as I've seen it in the past. I don't have a clue how to even check the baseline on this or how to advance timing if it is even possible. Is it?
(Computers)
I just changed another Opti and although it runs just fine (better actually) the highway mileage seems a couple of mpg lower than it had been on previous long hauls. Not at all bad, just not quite as high as I've seen it in the past. I don't have a clue how to even check the baseline on this or how to advance timing if it is even possible. Is it?
(Computers
)Last edited by 93VettePilot; May 14, 2011 at 03:59 PM.
Safety Car
Joined: Sep 2001
Posts: 4,149
Likes: 546
From: Glenbeulah Wi
Checking actual timing on an LT1 or LT4 is a pain in the rear. You need to make a TDC pointer and set actual TDC once you verify the actual TDC with a piston stop or some other method. There is no way to easily adjust the timing other then programming. I always indicate TDC on an LT1 to verify that the timing you are commanding is actual timing or is it off by some undefined number. I have seen LT1 timing as much as 27 degrees retarded when actual was compared to assumed.
Advanced
Joined: Apr 2011
Posts: 53
Likes: 0
From: Ft. Worth Texas
The msd opti allows +/- 5 degrees change with a turn of a screw. my msd digital 6 plus retards to 8 or 10 degrees max with 12 volts to pink wire. That's as much as I know. The last time I had a chip burned was in 2000 with ed wright. I called him the other day cause i have changed some things on my 92 and have a dead spot at 1700. He sold his dyno. I wish I knew how to tune myself or could find someone closer to dfw that is good. Anyway, I wish I could help you more. Good Luck! 
Instructor
Joined: May 2011
Posts: 102
Likes: 0
From: SE SD
The PCM gives you max timing to an extent now and uses the knock sensor to retard the timing for spark knock. I have read about the msd opti's advance coming apart on the camaro boards. If you want to add some timing the best way is with a tune. This will also give you an opportunity to tweak fueling. Even if you give the MSD unit the full 6 degrees of advance and the PCM determines it doesn't need it it will retard the timing as needed upto 15 degrees depending on operating conditions.
Last edited by thearborbarber; Jul 6, 2011 at 12:49 AM.
