Setting ignition timing
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Laughing Gas
Joined: Aug 2010
Posts: 1,049
Likes: 230
From: Amarillo, TX
Setting ignition timing
So I'm FINALLY getting everything put back together & am planning on firing my 400 for the 1st time after the rebuild. Just want to make sure I do everything correctly . I am using TMI pistons, a mild rv cam, stock heads & holley 670cfm street avenger. Also converted to HEI with a Proform distributor. Firing order is 1-3-7-2-6-5-4-8; dizzy turns counterclockwise when viewed from front of engine, & cylinder numbering is 1234 on passenger side from front to back & 5678 on driver side; Is this all correct? I was told a good starting point for initial Timing was 12 degrees BTDC? Does anyone have a good link to a timing article? I have a timing light, but no idea how to use it, so a basic how-to would be very helpful. Thanks!!!
Postmaster
Joined: Mar 2011
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From: Taxachusetts
Answers to all your questions is as you think - all correct. 12* BTDC on a slightly built M block is fine. You might want to go higher after break in.
The distributor's rotor should be pointing to or just past #1 plug wire with the piston on the compression stroke....the pointer at the balancer at zero when the distributor is set in place.
Ball park carb mixture adjustment is 1.5 turns out from seating. Fine tuning comes later.
Timing light use: Hook the + (red) and - (black) light cables to the + BATT (red) and - BATT (black). The clampy thing that has a hole in it connects to #1 plug wire. Squeeze the trigger and point the flashy end at the balancer when she's running - be careful! That'll show you where (in degrees) #1 cylinder is firing......10, 12, 14, etc.
The most important part on break in is to have the correct break in oil and to keep the RPMs about 1500 for 20 - 30 minutes.....varying the RPMs. Don't let her idle during break in!
The distributor's rotor should be pointing to or just past #1 plug wire with the piston on the compression stroke....the pointer at the balancer at zero when the distributor is set in place.
Ball park carb mixture adjustment is 1.5 turns out from seating. Fine tuning comes later.
Timing light use: Hook the + (red) and - (black) light cables to the + BATT (red) and - BATT (black). The clampy thing that has a hole in it connects to #1 plug wire. Squeeze the trigger and point the flashy end at the balancer when she's running - be careful! That'll show you where (in degrees) #1 cylinder is firing......10, 12, 14, etc.
The most important part on break in is to have the correct break in oil and to keep the RPMs about 1500 for 20 - 30 minutes.....varying the RPMs. Don't let her idle during break in!
Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 1,049
Likes: 230
From: Amarillo, TX
Thank you!! Does there need to be any timing tape or other marks put on the balancer for the timing light to work correctly? What are indications that the timing needs to be advanced or retarded?
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
You're welcome...
There are marks on the balancer already...or there should be. The timing light will work just fine by itself if hooked up right. Do you have the plain Jane type - regular inductive light or the fancy-*** dial back type?
Indications dictating advancing/retarding the ignition timing:
If you're reading somewhere around 25*- 30* BTDC then you should retard the ignition timing back to ~ 12* BTDC. If you're reading around 6*- 10* BTDC, advancing it to ~ 12* BTDC is in order. Won't get into "pinging" at the moment......
Can you post up the cam specs? Usually a "bigger" than stock cam requires more initial to make her happy.
Your new timing chain/gears are set "straight up," no?
There are marks on the balancer already...or there should be. The timing light will work just fine by itself if hooked up right. Do you have the plain Jane type - regular inductive light or the fancy-*** dial back type?
Indications dictating advancing/retarding the ignition timing:
If you're reading somewhere around 25*- 30* BTDC then you should retard the ignition timing back to ~ 12* BTDC. If you're reading around 6*- 10* BTDC, advancing it to ~ 12* BTDC is in order. Won't get into "pinging" at the moment......
Can you post up the cam specs? Usually a "bigger" than stock cam requires more initial to make her happy.
Your new timing chain/gears are set "straight up," no?
Postmaster
Joined: Mar 2011
Posts: 2,698
Likes: 7
From: Taxachusetts
Hopefully, you've gone through the break-in period, yes? If not, break in the engine first, then worry about the fine tuning stuff....
Anyway.....I personally like the "old school" timing lights better. Less moving parts to mess with.
When timing your engine, the vacuum advance should be disconnected and plugged....especially if you're using manifold vacuum. If using ported you really don't need to disconnect the vacuum advance...if you keep her at idle when timing her.....around 650-700 RPMs for a stick, 700-750 RPMs for an auto....since there's no vacuum at idle using ported vacuum. Most people disconnect/plug it anyway.
Ported or manifold vacuum? I would recommend going with ported unless you know your way around fine tuning the carb, getting/setting the right distributor weights, what you want for "all in" timing, etc, etc. It's up to you, really....but for now, stick with ported until you know how she runs.
Anyway.....I personally like the "old school" timing lights better. Less moving parts to mess with.
When timing your engine, the vacuum advance should be disconnected and plugged....especially if you're using manifold vacuum. If using ported you really don't need to disconnect the vacuum advance...if you keep her at idle when timing her.....around 650-700 RPMs for a stick, 700-750 RPMs for an auto....since there's no vacuum at idle using ported vacuum. Most people disconnect/plug it anyway.
Ported or manifold vacuum? I would recommend going with ported unless you know your way around fine tuning the carb, getting/setting the right distributor weights, what you want for "all in" timing, etc, etc. It's up to you, really....but for now, stick with ported until you know how she runs.
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Postmaster
Joined: Mar 2011
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From: Taxachusetts
Byrd.Dog:
I have to book now....I'll get back to you later (if no one else does) for any more Q/A.
Good luck!
I have to book now....I'll get back to you later (if no one else does) for any more Q/A.
Good luck!
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Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 1,049
Likes: 230
From: Amarillo, TX
Thanks for all the insight... got another question about firing my motor for the 1st time: I bought one of those ools that goes on your drill & fits the oil pump drive shaft to pre-lube the motor before starting. While running it, there was very little resistance at first, then it got much harder to turn. Oil pressure gauge shows 0 while drill is running. Gauge is autometer electrical hooked up via painless harness. Any quick way to verify oil pump is working properly?
Postmaster
Joined: Mar 2011
Posts: 2,698
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From: Taxachusetts
Hey, man! Shoot, I figgered you'd be up an' runnin' by now...!
Electric gauges - funny thing about them - the operative word here is 'electrical.' They won't show beans unless they have some voltage input - key is ON.
Anyway - what I do is before installing the valve covers, I use an electric, half inch chuck drill, set to run CCW and run it....getting the same results as you. Got progressively harder to turn....
Now, with the valve covers off, I could see the oil getting up the pushrods, through the rockers, etc. I would then turn the engine by hand CW 90* and do the drill deal again, watching for the oil to get up and around. I would then turn it 90* again, do the same deal. I would then turn the engine CCW to the compression stroke...(back 180*), do the drill thing one more time, then set the distributor in.
Make sure all tools are out of the way, check the firing order again, verify timing, prime the carb.....lock/load......FIRE!!!!
Merry Christmas and good luck!
Electric gauges - funny thing about them - the operative word here is 'electrical.' They won't show beans unless they have some voltage input - key is ON.
Anyway - what I do is before installing the valve covers, I use an electric, half inch chuck drill, set to run CCW and run it....getting the same results as you. Got progressively harder to turn....
Now, with the valve covers off, I could see the oil getting up the pushrods, through the rockers, etc. I would then turn the engine by hand CW 90* and do the drill deal again, watching for the oil to get up and around. I would then turn it 90* again, do the same deal. I would then turn the engine CCW to the compression stroke...(back 180*), do the drill thing one more time, then set the distributor in.
Make sure all tools are out of the way, check the firing order again, verify timing, prime the carb.....lock/load......FIRE!!!!
Merry Christmas and good luck!
Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 1,049
Likes: 230
From: Amarillo, TX
Thanks!! You know how it is - between work, the holidays, family, cooking, & wrenching on my other rides, i never seem to have enough time. Hopefully once I get the motor running it will motivate me to get everything else finished so I can get her back on the road. Been derelict in my driveway for almost 3 years!
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