Distributor and Balancer Experts Help!
Thread Starter
Tech Contributor
Joined: Oct 2008
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From: Custer, WI
Distributor and Balancer Experts Help!
I have been having problems with my 85 running rough lately. I decided to check the timing (for the 50th time) today.
I noticed something strange. If I set the car at 6 degrees BTDC, with the EST disconnected, at idle it will stay at 6 degrees, if I open the throttle up to about 1500 rpm, the balancer mark goes past the 12 degree btdc mark (my guess would be around 16 degrees btdc.) It goes even farther if I open it up more.
Isn't the timing supposed to stay dead on at 6 degrees no matter what RPM the engine is running?
Slipped balancer? Something wrong with distributor? Timing chain?
The car is tired, so there could be multiple problems here.
Thanks,
Jeremy
I noticed something strange. If I set the car at 6 degrees BTDC, with the EST disconnected, at idle it will stay at 6 degrees, if I open the throttle up to about 1500 rpm, the balancer mark goes past the 12 degree btdc mark (my guess would be around 16 degrees btdc.) It goes even farther if I open it up more.
Isn't the timing supposed to stay dead on at 6 degrees no matter what RPM the engine is running?
Slipped balancer? Something wrong with distributor? Timing chain?
The car is tired, so there could be multiple problems here.
Thanks,
Jeremy
Instructor
Joined: Dec 2006
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Hi,
Almost always with a few exceptions a internal gas combustion engine requires the spark lead/advance to increase with rpm. This is due to the relatively decresed time for combustion to occur. Also power and efficiency increases with timing.
Sounds like everything is normal.
92WhiteVetteGuy
Almost always with a few exceptions a internal gas combustion engine requires the spark lead/advance to increase with rpm. This is due to the relatively decresed time for combustion to occur. Also power and efficiency increases with timing.
Sounds like everything is normal.
92WhiteVetteGuy
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From: Overland Park Kansas
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And, from what the TGO guys tell me, vettes have more advance than their counterpart F-body cars.
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
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From: Custer, WI
Okay so that is normal for the car to have the advance without the EST. Can anybody tell me why my car is slow? Its like the car isn't getting spark advance, it doesn't have hardly any pickup.
I can't even spin the tires with my foot on the brake at WOT.
I can't even spin the tires with my foot on the brake at WOT.
Le Mans Master
Joined: Feb 2005
Posts: 5,146
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From: The Motor City
I noticed something strange. If I set the car at 6 degrees BTDC, with the EST disconnected, at idle it will stay at 6 degrees, if I open the throttle up to about 1500 rpm, the balancer mark goes past the 12 degree btdc mark (my guess would be around 16 degrees btdc.) It goes even farther if I open it up more.
Isn't the timing supposed to stay dead on at 6 degrees no matter what RPM the engine is running?
Isn't the timing supposed to stay dead on at 6 degrees no matter what RPM the engine is running?
I can't tell you why it won't spin the tires or is slow...sounds as though timing isn't the problem. It wouldn't be a a bad idea to get a scan/datalog to understand everything else that is going on.
Racer
Joined: Jul 2010
Posts: 308
Likes: 2
From: Kansas City MO
I noticed something strange. If I set the car at 6 degrees BTDC, with the EST disconnected, at idle it will stay at 6 degrees, if I open the throttle up to about 1500 rpm, the balancer mark goes past the 12 degree btdc mark (my guess would be around 16 degrees btdc.) It goes even farther if I open it up more.
Isn't the timing supposed to stay dead on at 6 degrees no matter what RPM the engine is running?
Isn't the timing supposed to stay dead on at 6 degrees no matter what RPM the engine is running?
I'd check the ignition module as I've seen other GM ones exhibit similar random timing events before going out - also if it's bouncing around a lot then check the timing chain for slack (you can pull cap, turn engine clockwise then counter clockwise and look for rotor movement) and check for loose distributor bushings.
OH - and if it was balancer - it would slip and look like it was advanced but NOT return to base reading.
Le Mans Master
Joined: Aug 2000
Posts: 8,838
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From: Australia
But FWIW just checked mine out of interest and it does the same as OP's.
With ESC disconnected ;static @6 ; goes to 12 when reved ('90 w/ 50K)
Thread Starter
Tech Contributor
Joined: Oct 2008
Posts: 3,729
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From: Custer, WI
I can datalog it with tunerpro rt. My BLMS are all over the map. It all started after the super ram swap, i can't find any vacuum leaks but there could be one.
As far as the timing chain goes would it be worth it to replace it? what kind of project am i looking at?
I want to build a 383 soon, I am stacking parts (just bought heads, Super ram, have crank & block) because i know this 350 is on its last leg.
This is what I have replaced:
Ignition module (tooth thing in dizzy)
Fuel pump
Fuel filter
ECM
cleaned off 2 grounds
cleaned MAF
replaced CTS (after old ECM told me it was -40 degrees)
As far as the timing chain goes would it be worth it to replace it? what kind of project am i looking at?
I want to build a 383 soon, I am stacking parts (just bought heads, Super ram, have crank & block) because i know this 350 is on its last leg.
This is what I have replaced:
Ignition module (tooth thing in dizzy)
Fuel pump
Fuel filter
ECM
cleaned off 2 grounds
cleaned MAF
replaced CTS (after old ECM told me it was -40 degrees)
Last edited by Pwnage1337; Aug 4, 2010 at 11:58 PM.
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From: Overland Park Kansas
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To the OP: The FSM says there is a backup system to provide ignition advance in the event the EST fails. It doesn't' say how/where, but you'd have to think it was mechanical in the distributor. That must account for the (small) advance seen when the EST is disconnected.
Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
LOL. Where DOES some of this stuff come from???
With my 86 Vette I use to play with the initial timing all the time with the timing connector disconnected. Tried the stock 6 Degrees BTDC, 8, 10, etc. Guys do this all the time.
Once done I locked down the dizzy, verified the setting hadn't changed, shut down the engine, reconnected the timing connector, cleared the stored and done.
Well, done except for the test drives with Diacom up and running while I logged and watched for knock retard.
Jake
With my 86 Vette I use to play with the initial timing all the time with the timing connector disconnected. Tried the stock 6 Degrees BTDC, 8, 10, etc. Guys do this all the time.
Once done I locked down the dizzy, verified the setting hadn't changed, shut down the engine, reconnected the timing connector, cleared the stored and done.
Well, done except for the test drives with Diacom up and running while I logged and watched for knock retard.
Jake
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From: Overland Park Kansas
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Did you even read this thread, Jake? 
If so, I'd be really curious what the heck you just responded to.
If so, I'd be really curious what the heck you just responded to.
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From: moraga ca
Safety Car
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Look harder
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From: Overland Park Kansas
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Le Mans Master
Joined: Feb 2000
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From: Kempner Texas
I can datalog it with tunerpro rt. My BLMS are all over the map. It all started after the super ram swap, i can't find any vacuum leaks but there could be one.
As far as the timing chain goes would it be worth it to replace it? what kind of project am i looking at?
I want to build a 383 soon, I am stacking parts (just bought heads, Super ram, have crank & block) because i know this 350 is on its last leg.
This is what I have replaced:
Ignition module (tooth thing in dizzy)
Fuel pump
Fuel filter
ECM
cleaned off 2 grounds
cleaned MAF
replaced CTS (after old ECM told me it was -40 degrees)
As far as the timing chain goes would it be worth it to replace it? what kind of project am i looking at?
I want to build a 383 soon, I am stacking parts (just bought heads, Super ram, have crank & block) because i know this 350 is on its last leg.
This is what I have replaced:
Ignition module (tooth thing in dizzy)
Fuel pump
Fuel filter
ECM
cleaned off 2 grounds
cleaned MAF
replaced CTS (after old ECM told me it was -40 degrees)
Jake
Last edited by JAKE; Aug 7, 2010 at 09:06 PM.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Race Director
Joined: Nov 2003
Posts: 12,221
Likes: 446
From: Overland Park Kansas
2020 Corvette of the Year Finalist (appearance mods)
C4 of Year Winner (appearance mods) 2019