Ignition timing problem
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Ignition timing problem
I finially got my create motor running good, but to do so I had to set the timing with a vacuum gage. I cranked the dist around until I got good vacuum and idle. When I check the timing (no vacuum advance) It's WAY off the mark. Looks like 25-30 degrees advanced. When I set the timing correctly with a light to 10 degrees, it pops out the carb and runs like crap. So what did I do wrong in assembling the engine that moved the timing mark so far off??
P.S.: the new Forum format really runs S-L-O-W. What happened???
P.S.: the new Forum format really runs S-L-O-W. What happened???
Safety Car
Joined: Jan 2001
Posts: 4,660
Likes: 3
From: South Central Louisiana
St. Jude Contributor
Re: Ignition timing problem (Duke94)
I finially got my create motor running good, but to do so I had to set the timing with a vacuum gage. I cranked the dist around until I got good vacuum and idle. When I check the timing (no vacuum advance) It's WAY off the mark. Looks like 25-30 degrees advanced. When I set the timing correctly with a light to 10 degrees, it pops out the carb and runs like crap. So what did I do wrong in assembling the engine that moved the timing mark so far off??
P.S.: the new Forum format really runs S-L-O-W. What happened???
P.S.: the new Forum format really runs S-L-O-W. What happened???
We played with my timing a bit on Saturday and the only time it would pop thru carb is when we where very close to 0 or in the negative, so you probably have less than 10. What is your total timing? I think 36 is the actual max recommended.
P.S. Progress my friend, progress.
Melting Slicks
Joined: Oct 2000
Posts: 3,023
Likes: 2
From: TEXASTEXASTEXASTEXAS TEXASTEXASTEXASTEXAS
St. Jude Contributor
Re: Ignition timing problem (Duke94)
You may want to make sure that the mark on the harmonic balancer is actually in the right place so that you're actually at TDC when it's lined up with the 0 mark on the scale.
JB
JB
Race Director
Joined: Mar 2001
Posts: 11,322
Likes: 1
From: Living in the Hartland
Re: Ignition timing problem (Duke94)
Also, you might have the wrong timing tab. You might need to get a tdc locator and check to make sure your are right on. Vac leak might also be something to check for.
Drifting
Joined: Jun 2001
Posts: 1,809
Likes: 0
Re: Ignition timing problem (Duke94)
Lars wrote a very good paper on timing it will give you a very good handle for trouble shooting this problem. I don't remember how to get to where it is but some one should remember.
Racer
Joined: Oct 2000
Posts: 311
Likes: 0
From: West Newton PA
Re: Ignition timing problem (Tominator)
Lars' articles on timing are at www.corvettefaq.com. It does sound like a slipped balencer, though. Hope that helps.
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Re: Ignition timing problem (JB)
I have removed the damper and compared it with the old one, and it is identical. Timing mark is in the same location relitive to the key. What else can it be?
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Burning Brakes
Joined: Oct 2001
Posts: 1,241
Likes: 4
From: Okinawa Okinawa
Re: Ignition timing problem (Duke94)
Once the damper is back on you may want to rotate the engine to TDC to ensure the damper hasn't slipped. Take out all the sparks plugs firs, much easier. Besides that check out lars paper. Can't remember who told me, mountian motor I think, but he said that depending on what type of engine you have and the mods it may be more than 14 BTDC. 25-30 is too much but wherever it runs the best set it. I think your damper may have slipped a little.
Thread Starter
Le Mans Master
Joined: Mar 2001
Posts: 6,640
Likes: 287
From: Ann Arbor Michigan
Re: Ignition timing problem (Duke94)-update
Here is a response I received from Lars, it is worth passing on since it exactly what my problem was.
"Initial advance at idle is irrelevant - where is your total timing set? Many performance engines require about 20-25 degrees initial advance for best performance, but the total should remain around 36. If you're running one of my curved distributors, it is possible for the advance to come in very quick. If you have an engine with a bit of a cam, and it's idling at about 1000 rpm, chances are good that a bit of the advance is already cranked in at idle. This will easily give you an indication of 20-25 degrees initial advance, but you need to disregard this and check the total to verify 36 with vac advance disconnected."
"If your total timing is grossly exceeding 36 in order to get the engine to run right, you have some kind of problem - most likely a TDC marking issue. If this is the case, you need to go in and re-determine TDC and mark it correctly. My guess is that you probably won't have a problem once you set up and verify your total at 36 and disregard the initial since initial timing is completely irrelevant on a quick-advance timing curve."
"Initial advance at idle is irrelevant - where is your total timing set? Many performance engines require about 20-25 degrees initial advance for best performance, but the total should remain around 36. If you're running one of my curved distributors, it is possible for the advance to come in very quick. If you have an engine with a bit of a cam, and it's idling at about 1000 rpm, chances are good that a bit of the advance is already cranked in at idle. This will easily give you an indication of 20-25 degrees initial advance, but you need to disregard this and check the total to verify 36 with vac advance disconnected."
"If your total timing is grossly exceeding 36 in order to get the engine to run right, you have some kind of problem - most likely a TDC marking issue. If this is the case, you need to go in and re-determine TDC and mark it correctly. My guess is that you probably won't have a problem once you set up and verify your total at 36 and disregard the initial since initial timing is completely irrelevant on a quick-advance timing curve."
