Timing Light
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
Likes: 0
From: Forty Fort PA
Timing Light
Hi all.
Anyone notice an issue with connecting their digital timing light to the back of the alternator for power?
I have a new light and I am trying to set the timing on my BB. when I first connected the light, it showed correct RPM (agreed with tach) but showed timing around 40* BTC with the vac disconnected. I tried to retard to below 20* but I get backfire (exhaust). I tried to set 33* with vac (18 init + 15 vac.). Best I could get to run decently was around 40*.
Marks on damper were right on before I installed the heads and I have not reason to think they moved. The cam was right on when checked with a degree wheel set-up.
I have one of the dist caps that puts the wire attachment points in the same order as the plugs and on the same side. Some refer to these as "corrected". I am going to try a standard cap.
If you don't get the power for your timing light from the alternator connection, where do you connect?
Thanks for looking
Langg
Anyone notice an issue with connecting their digital timing light to the back of the alternator for power?
I have a new light and I am trying to set the timing on my BB. when I first connected the light, it showed correct RPM (agreed with tach) but showed timing around 40* BTC with the vac disconnected. I tried to retard to below 20* but I get backfire (exhaust). I tried to set 33* with vac (18 init + 15 vac.). Best I could get to run decently was around 40*.
Marks on damper were right on before I installed the heads and I have not reason to think they moved. The cam was right on when checked with a degree wheel set-up.
I have one of the dist caps that puts the wire attachment points in the same order as the plugs and on the same side. Some refer to these as "corrected". I am going to try a standard cap.
If you don't get the power for your timing light from the alternator connection, where do you connect?
Thanks for looking
Langg
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
I usually pick up power from the horn relay under the left fender just forward of the master cylinder on my 69. The alternator output stud has a boot over it and it's difficult to remove and I'm lazy.
Tech Contributor
Joined: Aug 1999
Posts: 14,384
Likes: 6,411
From: At my Bar drinking and wrenching in Lafayette Colorado
I have a new light and I am trying to set the timing on my BB. when I first connected the light, it showed correct RPM (agreed with tach) but showed timing around 40* BTC with the vac disconnected. I tried to retard to below 20* but I get backfire (exhaust). I tried to set 33* with vac (18 init + 15 vac.). Best I could get to run decently was around 40*.
Langg
Langg
BB's like to run at about 38 - 40 total mechanical. If your 40-degree number is total, it looks good - I don't see that you have an issue.
Lars
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Thread Starter
Racer
Joined: Aug 2005
Posts: 456
Likes: 0
From: Forty Fort PA
Lars-
I would be happy if the total is 40* but I am checking at 950RPM and the mechanical system looks ok. I think the 20* mechanical will be on top of that. Still don't understand the 40 at idle. Something must be amiss.
Ignition is a plain vanilla HEI. No MSD
Langg
I would be happy if the total is 40* but I am checking at 950RPM and the mechanical system looks ok. I think the 20* mechanical will be on top of that. Still don't understand the 40 at idle. Something must be amiss.
Ignition is a plain vanilla HEI. No MSD
Langg
Racer
Joined: Dec 2008
Posts: 297
Likes: 19
From: arlington TX
Hi,
You say that this is a 'new timing light'. Was your old one the same type - timing **** on the timing light?
Not trying to be a smart a**, but when you have 20 degrees (or anything other than 0) dialed in on the timing light, you time off the "0" mark on the balancer, right?
Just checking.
I've seen 50 degrees of timing on my engines, then realize that I am trying to use the wrong marks - 30 on the timing light and using the 20 degree mark on the balancer.
Good luck.
walt
You say that this is a 'new timing light'. Was your old one the same type - timing **** on the timing light?
Not trying to be a smart a**, but when you have 20 degrees (or anything other than 0) dialed in on the timing light, you time off the "0" mark on the balancer, right?
Just checking.
I've seen 50 degrees of timing on my engines, then realize that I am trying to use the wrong marks - 30 on the timing light and using the 20 degree mark on the balancer.
Good luck.
walt
Drifting
Joined: May 2012
Posts: 1,353
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From: Calgary Alberta
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Try checking the timing at idle, with the timing light set to 0*. Then at idle, turn the dial until the 0 marks on both the tab and the balancer line up- that is your initial setting. Then increase the RPM to 3000 and bring the dial up again until the marks are lined up. That's your TOTAL. Vacuum disconnected.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
Likes: 0
From: Forty Fort PA
With timing light set to 0* advance and the vacuum disconnected, the marks show 45* BTC. If I retard it, I get popping at the exhaust. I think it should be possible to idle in the 0-10* range.
So, I will once again verify that the timing marks are in the correct position. If TDC is correctly indicated, what possibly can be the cause? If the cam was off a tooth or two, what would be the effect?
BTW, the harmonic balancer is a Fluidamper 800101. There is no way for the outside to slip relative to the mounting and only one keyway.
Langg
So, I will once again verify that the timing marks are in the correct position. If TDC is correctly indicated, what possibly can be the cause? If the cam was off a tooth or two, what would be the effect?
BTW, the harmonic balancer is a Fluidamper 800101. There is no way for the outside to slip relative to the mounting and only one keyway.
Langg
Thread Starter
Racer
Joined: Aug 2005
Posts: 456
Likes: 0
From: Forty Fort PA
Just to let everyone know...
The issue turned out to be the "corrected" distributor cap I was using. I put the original cap on and the problem went away. I was able to set the initial timing to 16* + 20 mechanical and 24 vacuum at idle.
Road test next.
Langg
The issue turned out to be the "corrected" distributor cap I was using. I put the original cap on and the problem went away. I was able to set the initial timing to 16* + 20 mechanical and 24 vacuum at idle.
Road test next.
Langg