Ignition timing

[old guys rule]

I may have asked this before I don't remember, if so please forgive. My question is I see a lot of guys on this site who set their initial timing on their 440s way more advanced then the manual calls for. I'm wondering what to set mine at. Thanks mild build, pure Street car.

 

[Cranky]

Give it what it wants. A lot depends on what it'll like...for instance, compression, how much psi the cam generates at low rpm, what the combination is. The book is for engines that were stock and then even some of them didn't like what the 'book' said to do.

 

[WileERobby]

Exactly. I like to just set my total advance. Then, adjust centrifugal as needed. What the Crankman says is spot on, the factory used settings in some circumstances for emissions purposes.

 

[BeepBeepRR]

I set my friends 383 by the book at 5 degrees BTDC and it was a pooch and wouldn't even pull itself out of the driveway. 10 is a good starting place. But the 383 is at 15 right now and loves it.

 

[Don Frelier]

I would start at 20 but yes your total timing will be high so you will need to limit the mechanical advance.

 

[moparedtn]

Stockity stock stock big blocks from say the late 60's like to sit around 10-12BTDC at idle
(hose removed and plugged at carb, of course) - but that doesn't matter nearly as much
as your "all-in" advanced timing.
If you have anything near a stock distributor on the thing, get some timing tape on the
harmonic balancer (or just do what I did, marking the balancer at 10 degree intervals by
measurement and a Sharpie).

If your centrifugal advance is working decently in the distributor, buzz that rascal up to
around 2500RPM and check your "all in" total advance there.
Most of these stock animals like anywhere from 32-36 degrees total advanced timing; play
with it some and see where it's happiest (smoothest) at that RPM.
The engine will tell you...(and you can always play along at home by hooking up a vacuum
gauge for verification, as best vacuum is typically most smooth).

Then whatever the timing is from there when you let it back down to idle is what it is....
provided the advance works, it'll probably be somewhere in the mid-teens BTDC.

Set it and forget it.

 

[old guys rule]

Stockity stock stock big blocks from say the late 60's like to sit around 10-12BTDC at idle
(hose removed and plugged at carb, of course) - but that doesn't matter nearly as much
as your "all-in" advanced timing.
If you have anything near a stock distributor on the thing, get some timing tape on the
harmonic balancer (or just do what I did, marking the balancer at 10 degree intervals by
measurement and a Sharpie).

If your centrifugal advance is working decently in the distributor, buzz that rascal up to
around 2500RPM and check your "all in" total advance there.
Most of these stock animals like anywhere from 32-36 degrees total advanced timing; play
with it some and see where it's happiest (smoothest) at that RPM.
The engine will tell you...(and you can always play along at home by hooking up a vacuum
gauge for verification, as best vacuum is typically most smooth).

Then whatever the timing is from there when you let it back down to idle is what it is....
provided the advance works, it'll probably be somewhere in the mid-teens BTDC.

Set it and forget it. [/QUO thanks for the help

 

[old guys rule]

Thanks for the help guys.

 

[TopBanana72]

Stockity stock stock big blocks from say the late 60's like to sit around 10-12BTDC at idle
(hose removed and plugged at carb, of course) - but that doesn't matter nearly as much
as your "all-in" advanced timing.
If you have anything near a stock distributor on the thing, get some timing tape on the
harmonic balancer (or just do what I did, marking the balancer at 10 degree intervals by
measurement and a Sharpie).

If your centrifugal advance is working decently in the distributor, buzz that rascal up to
around 2500RPM and check your "all in" total advance there.
Most of these stock animals like anywhere from 32-36 degrees total advanced timing; play
with it some and see where it's happiest (smoothest) at that RPM.
The engine will tell you...(and you can always play along at home by hooking up a vacuum
gauge for verification, as best vacuum is typically most smooth).

Then whatever the timing is from there when you let it back down to idle is what it is....
provided the advance works, it'll probably be somewhere in the mid-teens BTDC.

Set it and forget it.

So, with this method, you would leave the vacuum advance line connected, correct?

 

[moparedtn]

So, with this method, you would leave the vacuum advance line connected, correct?

Once you've got things sorted out, sure - hook the vacuum advance back up if you want to.
A lot of folks (including myself) don't, for various reasons - but if we're talking stock setup, sure
go ahead.

 

[Dragon Slayer]

2500rpm won't give you total on a stock distributor set up. The manual gives distributor values not crankshaft. You will need to spin motor as high as 5000 rpm to see total advance at the crank shaft.

I think it is wise to first open your distributor and determine what springs, and what the mech adv is. Later emission type starting in 68 could be 15deg distr for 30-32 at crank total. The Initial timing was in the 0 deg range.

If the heavy spring removed or replace with a softer spring, you will see total come in at a much lower RPM.

Make sure you adjust idle back down after increasing initial timing, before plugging vacuum back in. If exposed to engine vacuum timing will advance much more. Which probably would not work well with a stock motor as you stated you have.

 

[TopBanana72]

Once you've got things sorted out, sure - hook the vacuum advance back up if you want to.
A lot of folks (including myself) don't, for various reasons - but if we're talking stock setup, sure
go ahead.

No, I meant leave the vacuum hose connected during the timing session?

 

[moparedtn]

No, I meant leave the vacuum hose connected during the timing session?

Pretty sure that one got answered a few times, but in case not:
Vacuum advance hose is always disconnected, source plugged off at the carb when setting/checking
base and mechanical advanced timing.
Once you get those sorted then sure, hook the thing back up and check its' vacuum advance if you like.

 

[ChargerChad]

My ‘71 383 likes 10 degrees. I had it up to 12 last week and hot starting improved but I’d get slight pinging under a load at part throttle and you could tell it just didn’t like it. Pulled two degrees back out and it purrs like a kitten.

 

[Crackedback]

My ‘71 383 likes 10 degrees. I had it up to 12 last week and hot starting improved but I’d get slight pinging under a load at part throttle and you could tell it just didn’t like it. Pulled two degrees back out and it purrs like a kitten.

You really should to set it for what the engine wants at idle and limit mechanical. If it liked 12 initial I bet it would like 14 initial even more. You're allowing total to dictate the idle which isn't the best way to do things.

You know where it starts to ping, so that is your total number. Find that and work backwards at this point to get initial timing levels. Modify the mechanical advance to hit your total number once you have the initial number sorted out.

JMO ignition timing for an engine is like building a house. Total is the roof. Do you build the roof first? No. you build the foundation (initial) first and build up to the roof. Poor initial timing cause other systems to be crutched to cover the timing issues.

If it runs and you're happy, all good, it could be better based on your comment.

 

[threewood]

Pretty sure that one got answered a few times, but in case not:
Vacuum advance hose is always disconnected, source plugged off at the carb when setting/checking
base and mechanical advanced timing.
Once you get those sorted then sure, hook the thing back up and check its' vacuum advance if you like.

I think it depends on whether he is hooked to ported or manifold vacuum.

As for timing, hook up a vacuum gauge and adjust advance until you get close to max vacuum. You'll see it plateau. Back it off a bit and tighten distributor. This will get you really close on initial timing. But this also raises your total timing. Total for a B / RB should be in the neighborhood of 37/38*. You can get a timing plate that fits over the distributor weights to get this or you can weld the slots in the stock distributor advance. Make sure it starts without bucking the starter. Drive it to make sure it doesn't ping.

 

[ChargerChad]

You really should to set it for what the engine wants at idle and limit mechanical. If it liked 12 initial I bet it would like 14 initial even more. You're allowing total to dictate the idle which isn't the best way to do things.

You know where it starts to ping, so that is your total number. Find that and work backwards at this point to get initial timing levels. Modify the mechanical advance to hit your total number once you have the initial number sorted out.

JMO ignition timing for an engine is like building a house. Total is the roof. Do you build the roof first? No. you build the foundation (initial) first and build up to the roof. Poor initial timing cause other systems to be crutched to cover the timing issues.

If it runs and you're happy, all good, it could be better based on your comment.

That makes sense. I was driving it earlier today and my ping is still there, just slightly, under part throttle on uphills. I’ve got a 650 Edelbrock AVS-2 on it, and I’m planning on going a step richer just to make sure that’s not the issue. If not, My distributor is the 440 Source Street distributor so I’ll have to call them to figure out how to pull back the total.

 

[hunt2elk]

That makes sense. I was driving it earlier today and my ping is still there, just slightly, under part throttle on uphills. I’ve got a 650 Edelbrock AVS-2 on it, and I’m planning on going a step richer just to make sure that’s not the issue. If not, My distributor is the 440 Source Street distributor so I’ll have to call them to figure out how to pull back the total.

I would be they have adjustable slots just like most other distributors. Shorten the slot to tighten up the total advance.