Timing an engine without disconnecting....
Thread Starter
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
Timing an engine without disconnecting....
I was wondering what happens if you don't disconnect the tan dist. wire before you time the engine?
My dad has timed both mine and my brothers 305 and the timing seems fine.
He didn't disconnect any wires though before doing it.
My dad has timed both mine and my brothers 305 and the timing seems fine.
He didn't disconnect any wires though before doing it.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
It would depend on what you timed it TO. When I set my base timing at 6° BTDC with the EST disconnected, it reads about 18° to 22° BTDC with the EST connected. If you are compensating, fine. If not, you are setting your timing, way retarded, if there are no problems with the ignition, ESC, and EST systems.
RACE ON!!!
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by RRT vette
When you disconnect the EST wire is cuts of the ECM from setting the timing where it was. There for, not disconnecting shouldn't do any good.
RACE ON!!!
Thread Starter
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
soooooo
so if Iam not having problems will the cars computer compensate and thats why I don't feel anything wrong? or should I reset the timing?
Thread Starter
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
Where is that EST wire on a 1990?
Just want to be sure Iam disconnecting the right wire....
Where is the EST wire on a 1990?
What does EST stand for?
Where is the EST wire on a 1990?
What does EST stand for?
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
You're timing will be retarded to the tune of 14-20 degrees or more.
Light load timing at idle should be around 20-26 degrees BTDC, which will be effectively reduced to 6 degrees (if thats what it was set to).
Note: Retarded ignition timing should help your NOx problem, but will kill your fuel economy and performance. You may want to try this trick if you need to get it to pass.
Otherwise, I think you will need to add fuel, as I've mentioned in your other post.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by CFI-EFI
HUH???
RACE ON!!!
RACE ON!!!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
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
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by XtremeVette
so if Iam not having problems will the cars computer compensate and thats why I don't feel anything wrong? or should I reset the timing?
RACE ON!!!
Thread Starter
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
ok so ....how?
ok, so anybody know the correct procedure to time an L98 engine without a timing light? sorry I don't own one. Can you do it by ear? I mean I just need to be fairly close right? In any case, cant' be any worst then it is doing it by ear WITH the EST wire still connected.
How have you pros done it?
How have you pros done it?
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by RRT vette
When not disconnecting it you are allowing the ECM to retard timing and it will not be set properly.
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by XtremeVette
ok, so anybody know the correct procedure to time an L98 engine without a timing light?
RACE ON!!!
Racer
Joined: May 2006
Posts: 286
Likes: 0
From: Alpine California
Extremevette, your pretty much just wasting your time without a timing light. Not saying it cant be done, but it takes a LOT of experience and trial and error! I've been doing this for twenty years (err...almost thirty years. Cr@p, I'm getting old!!!! 
And yeah, I'm sure there are plenty of guys on here older than me, who are going to call me a young pup, etc... but Oh well.) and other than very small adjustments out on a test drive, I always use a light! Yopu'de probably be better off just paying a local shop to do it for you, shouldn't cost more than $20 to $30 bucks, don't let them charge you more than .5 hrs to do it, it doesn't take that long!
And yeah, I'm sure there are plenty of guys on here older than me, who are going to call me a young pup, etc... but Oh well.) and other than very small adjustments out on a test drive, I always use a light! Yopu'de probably be better off just paying a local shop to do it for you, shouldn't cost more than $20 to $30 bucks, don't let them charge you more than .5 hrs to do it, it doesn't take that long!
Thread Starter
Original Founding Member!
Joined: Jul 1999
Posts: 9,037
Likes: 88
From: Granby, MA
Cruise-In 1, 3, 9. 10 & 11 Veteran
ok gotcha....gonna borrow the timing light....whats next
ok Iam gonna borrow the timing light....whats next...sorry to sound so needy, but I have never timed a car before...one thing that has eluded me. Never had to do it...lol
Melting Slicks
Joined: Aug 2003
Posts: 3,395
Likes: 393
From: Lakeville MI
Get a timing light, or borrow one its the only correct method. You can't really "power time" these cars since they will retard timing during knock.
But this may work if the distributor has not been removed and reclocked in a non standard orientation (I would not rely on this but its worth looking at your cap):
In my car, with 6 degrees of advance and the est disconnected, the distributor is sitting very nearly "straight" with respect to the longitudinal axis of the car. 4 degrees would be almost perfectly "straight". So I'm slightly advanced (read counterclockwise) of perfectly straight at 6 degrees.
I've considered resetting my base timing in the chip to 4 degrees just so I can have the distributor perfectly oriented, but it already very close to being spot on.
Look at the distributor cap from above (under the little tpi cover plate). There is a connector block that protrudes from the side of the cap with various connections for tach bat etc. If this is pointing directly to the driver's side of the car you should be in the vicinity of 4-6 degrees.
Remember this only works if the distributor orientation has not already been interfered with.
But this may work if the distributor has not been removed and reclocked in a non standard orientation (I would not rely on this but its worth looking at your cap):
In my car, with 6 degrees of advance and the est disconnected, the distributor is sitting very nearly "straight" with respect to the longitudinal axis of the car. 4 degrees would be almost perfectly "straight". So I'm slightly advanced (read counterclockwise) of perfectly straight at 6 degrees.
I've considered resetting my base timing in the chip to 4 degrees just so I can have the distributor perfectly oriented, but it already very close to being spot on.
Look at the distributor cap from above (under the little tpi cover plate). There is a connector block that protrudes from the side of the cap with various connections for tach bat etc. If this is pointing directly to the driver's side of the car you should be in the vicinity of 4-6 degrees.
Remember this only works if the distributor orientation has not already been interfered with.
Last edited by tequilaboy; Jun 27, 2006 at 02:40 PM.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by XtremeVette
ok Iam gonna borrow the timing light....whats next...sorry to sound so needy, but I have never timed a car before...one thing that has eluded me. Never had to do it...lol
RACE ON!!!
Le Mans Master
Joined: Oct 2003
Posts: 6,130
Likes: 2
From: seattle WA
47 yrs of turning wrenches it's a very easy process, first locate the timing mark on the harmonic balancer..I painted the grove white, easier for me to see, also on the timing indicator above the balancer..locate 6* BTDC, I marked it as well. Then disconnect the EST, the wire described to you, connect the timing light to number 1 and other connections to battery, losen the dist. hold down just lose enough to turn, start car..set timing, tighten hold down, at this point I re-check timing, turn car off, reconnect EST..restart car, You may have thrown a code now SES light, just disconnect the neg. battery terminal for a few minutes.Actually, for clarification the ECM will retard timing if the knock sensor reads to high and sends that info to the ECM. And yep FSM. factory service manuals year specific ar a must have if wrenching.
Last edited by rick lambert; Jun 27, 2006 at 02:48 PM.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Sounds like all you need now is a timing light and a 14mm or distrubitor wrench to get the job done. And as Rick said don't loosen the distrubitor hold down bolt too much or the distrubitor will turn when cranking and running. Just loose it enough that you have to give a little effort to turn the distrubitor.