ignition timing issue.
Thread Starter
Instructor
Joined: Jan 2012
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From: some hole in the ground town- camp verde:) arizona
ignition timing issue.
initial timing is set at 25 advanced and it still wants more at idle. i can't give it gas from a stop or it dies. once i get it rolling it has plenty of power. hit the gas and it backfires through the carb and dies. not sure what is going on here. took it to a mechanic who set it at 8, adjusted the carb and it ran great for the day, but next day was back to the same. at 8 degrees advanced it runs like crap. died in an intersection when i barely touched the gas.
one thing i find strange it that even at 25 degrees it doesn't buck against the starter. fires right up, no problem.
when i rev it at idle, with a timing light, i can watch it advance normally up to 32 or so.
cam shaft is a comp cams xe262h-10 if it makes any difference.
one thing i find strange it that even at 25 degrees it doesn't buck against the starter. fires right up, no problem.
when i rev it at idle, with a timing light, i can watch it advance normally up to 32 or so.
cam shaft is a comp cams xe262h-10 if it makes any difference.
Race Director
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1. Excuse this question but you definitely having the timing light hooked up to the cylinder closest to the front of the car on the drivers side?
2. Have you looked closely at the rubber bond on the harmonic balancer to see if the outter ring has slipped.
3. You are setting the timing with the vacuum advance disconnected?
2. Have you looked closely at the rubber bond on the harmonic balancer to see if the outter ring has slipped.
3. You are setting the timing with the vacuum advance disconnected?
Thread Starter
Instructor
Joined: Jan 2012
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From: some hole in the ground town- camp verde:) arizona
yes it's hooked to the #1 cylinder
i've considered that but then excused it since it will idle fine at 8 degrees and moves up to 32 degrees etc. i don't believe it has slipped.
and yes timing was set w/out vac advance hooked up.
i was wondering if this could be air fuel ratio or if it is strictly a timing issue.
i've considered that but then excused it since it will idle fine at 8 degrees and moves up to 32 degrees etc. i don't believe it has slipped.
and yes timing was set w/out vac advance hooked up.
i was wondering if this could be air fuel ratio or if it is strictly a timing issue.
Thread Starter
Instructor
Joined: Jan 2012
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From: some hole in the ground town- camp verde:) arizona
brand new carburetor straight out of the box. could the pump be not giving the correct amount of gas for the size motor?
leaving the library, be back tomorrow
leaving the library, be back tomorrow
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initial timing is set at 25 advanced and it still wants more at idle. i can't give it gas from a stop or it dies. once i get it rolling it has plenty of power. hit the gas and it backfires through the carb and dies. not sure what is going on here. took it to a mechanic who set it at 8, adjusted the carb and it ran great for the day, but next day was back to the same. at 8 degrees advanced it runs like crap. died in an intersection when i barely touched the gas.
one thing i find strange it that even at 25 degrees it doesn't buck against the starter. fires right up, no problem.
when i rev it at idle, with a timing light, i can watch it advance normally up to 32 or so.
cam shaft is a comp cams xe262h-10 if it makes any difference.
one thing i find strange it that even at 25 degrees it doesn't buck against the starter. fires right up, no problem.
when i rev it at idle, with a timing light, i can watch it advance normally up to 32 or so.
cam shaft is a comp cams xe262h-10 if it makes any difference.
ian from australia
Thread Starter
Instructor
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From: some hole in the ground town- camp verde:) arizona
just built the motor, the carb is a holley 3310- 750 cfm vac secondaries. intake is a weiand stealth. heads and intake are ported. block bored to .040 over. world product sportsman 2 heads.
no vacuum leaks that i know of. finally have vacuum staying pretty steady at idle.
no vacuum leaks that i know of. finally have vacuum staying pretty steady at idle.
Le Mans Master
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From: charlotte north carolina
Lars has a Tech Tip #3 concerning lean and rich off-idle stumbles in his excellent "How to Tune a Q-Jet (basic)" paper. Disconnect the accelerator pump lever and try to rev the engine slightly. If it responds better without the pump, it's too rich. If it responds more poorly, it's too lean. If there's no change, the pump is inoperative.
Thread Starter
Instructor
Joined: Jan 2012
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From: some hole in the ground town- camp verde:) arizona
Lars has a Tech Tip #3 concerning lean and rich off-idle stumbles in his excellent "How to Tune a Q-Jet (basic)" paper. Disconnect the accelerator pump lever and try to rev the engine slightly. If it responds better without the pump, it's too rich. If it responds more poorly, it's too lean. If there's no change, the pump is inoperative.
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From: New Or-leens Loo-z-anna
Le Mans Master
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From: League City Tx
It's definitely timing related.
You need to verify your timing mark at "0" is actually true TDC. Then set your timing from there. Nothing wrong with it at 25* initial if the engine starts ok. Make sure you are disconnecting the vacuum advance when you are setting the initial timing though. I have seen vacuum advances cause some screwy stuff with idle in park to idle in gear transitions...(idle speed drops->vacuum drops->timing drops->idle speed drops more -> this cycle repeats until sometimes it dies).
Make sure your idle mix screws and idle speed is set correctly, then move onto timing/dizzy diagnosis. Isolate anything vacuum related until after the timing is set right.
FWIW, I just set the timing on my dad's 65' 396 car with TI ignition, I set his total timing at 33* and his initial timing landed at 21* with the stock distributor curve and no vac advance. Completely stock distributor and it yields 21* initial/mechanical. Pretty good Id say.
Keep trying things and report back. First verify TDC is 0 on the tab.
You need to verify your timing mark at "0" is actually true TDC. Then set your timing from there. Nothing wrong with it at 25* initial if the engine starts ok. Make sure you are disconnecting the vacuum advance when you are setting the initial timing though. I have seen vacuum advances cause some screwy stuff with idle in park to idle in gear transitions...(idle speed drops->vacuum drops->timing drops->idle speed drops more -> this cycle repeats until sometimes it dies).
Make sure your idle mix screws and idle speed is set correctly, then move onto timing/dizzy diagnosis. Isolate anything vacuum related until after the timing is set right.
FWIW, I just set the timing on my dad's 65' 396 car with TI ignition, I set his total timing at 33* and his initial timing landed at 21* with the stock distributor curve and no vac advance. Completely stock distributor and it yields 21* initial/mechanical. Pretty good Id say.
Keep trying things and report back. First verify TDC is 0 on the tab.