Timing problem, Balancer, Timing Mark?
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Joined: Jan 2005
Posts: 10,404
Likes: 492
From: Hurst, Texas
Car: 1983 G20 Chevy
Engine: 305 TPI
Transmission: 4L60
Axle/Gears: 14 bolt with 3.07 gears
Timing problem, Balancer, Timing Mark?
Crazy engine tuning problem.
I recently changed my timing cover seal, in the process my original 1983 balancer hit the trash bin. I bought a brand new balancer that is supposed to be the right one for my engine.
Well, my engine seemed to be running a little rough at idle lately. The cap, rotor, wires, plugs were all new when I built the engine in May. Checked the timing with the set timing wire disconnected. It is at 6*, which matches what I have programmed in my chip. Plug the wire back in, same old rough idle.
For grins I decide to time it by ear with the ECM in control of the timing. Checked the timing and at idle it was at 25* when I disconnected the timing wire. Checked it with the wired connected and the timing was at 52*
52-25=27*. 27* pretty much matches what I have commanded in the spark table at 40-50 KPA. Engine DEAD smooth, the idle picked up, the vacuum actually came up to 16 in/hg at idle from 13.
I then set the timing back at 6*, plug the timing wire, the dull sounding/rough idle is back.
I timed it once again by ear, disconnected the timing wire. 24*
I guess the main question is how many different balancer combinations were there in the 1980s on the 305? I can think of atleast 2-3. How much difference is there between the balancer/marker, IF you get the wrong balancer?
I recently changed my timing cover seal, in the process my original 1983 balancer hit the trash bin. I bought a brand new balancer that is supposed to be the right one for my engine.
Well, my engine seemed to be running a little rough at idle lately. The cap, rotor, wires, plugs were all new when I built the engine in May. Checked the timing with the set timing wire disconnected. It is at 6*, which matches what I have programmed in my chip. Plug the wire back in, same old rough idle.
For grins I decide to time it by ear with the ECM in control of the timing. Checked the timing and at idle it was at 25* when I disconnected the timing wire. Checked it with the wired connected and the timing was at 52*
52-25=27*. 27* pretty much matches what I have commanded in the spark table at 40-50 KPA. Engine DEAD smooth, the idle picked up, the vacuum actually came up to 16 in/hg at idle from 13. I then set the timing back at 6*, plug the timing wire, the dull sounding/rough idle is back.
I timed it once again by ear, disconnected the timing wire. 24*
I guess the main question is how many different balancer combinations were there in the 1980s on the 305? I can think of atleast 2-3. How much difference is there between the balancer/marker, IF you get the wrong balancer?
Joined: Sep 2005
Posts: 27,866
Likes: 2,428
Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
The 2 most common timing mark locations are about 30 degrees apart, I forget the exact difference. Sounds like you might have that mismatch. I'm not sure whether the 1:30 setup came on 305s in that time frame; most all I've ever worked with were the 12:30 version.
Remember that the crank keyway is exactly aligned with the #1 rod throw. If you can see that easily without too much effort, you can use it to estimate if your mark is right. If your balancer is a 1:30, the timing mark on it will align closely with the keyway. If the balancer is the 12:30 version, the mark will be about 30 degrees counterclockwise from the keyway, viewed from the front. The fixed timing tab should match whichever one you've got obviously.
Having a 1:30 tab and a 12:30 balancer will put your timing somewhere near 30 degrees too late, if set by the mark. That sounds like what you might have.
Other than that, just observe the #1 piston, and see where the mark is when #1 is actually at TDC.
Remember that the crank keyway is exactly aligned with the #1 rod throw. If you can see that easily without too much effort, you can use it to estimate if your mark is right. If your balancer is a 1:30, the timing mark on it will align closely with the keyway. If the balancer is the 12:30 version, the mark will be about 30 degrees counterclockwise from the keyway, viewed from the front. The fixed timing tab should match whichever one you've got obviously.
Having a 1:30 tab and a 12:30 balancer will put your timing somewhere near 30 degrees too late, if set by the mark. That sounds like what you might have.
Other than that, just observe the #1 piston, and see where the mark is when #1 is actually at TDC.
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