440 Engine tuning suggestions

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69dodgedart360

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Good Morning FABO,

I have a 440 that was rebuilt about a year ago and need some help and suggestions about a "dieseling" after i turn the key off.

Its a 69 440 block with the following
10.7:1 compression
Stock 440 source heads
holley street dominator dual plane
Howards cams hydraulic roller 230/236@.050 .545 lift
Mopar Performance electronic ignition distributor with orange box module
Holley stteet avenger 770 vacuum secondary
Dougs headers
champion spark plugs recommended by 440source

The issue I am having is it diesels after I turn the key off. I have played around with the timing but unless I drop the idle speed to like 650-700 in park (which drops even further in gear) to where it is struggling, it will always diesel.

What should my initial base timing be for a performance engine like this?

What should it idle at in park?

Is my compression ratio too high for california 91 octane and contributing to this dieseling?

Other than the dieseling after shut off, it runs great at cruise, part throttle and WOT. Car does not run hot either.

Ive built other engines before and never had this problem. Kinda frustrating.

Thank you to all in advance for the help
 
Check that you have the correct spark plugs and not something hotter, make the idle mix richer, less timing advance for the rpm but a spec for a '69 440 auto is 5 btdc at 650 (with full load i.e. headlights, fans, ac if you have it, etc). Run the best fuel available.
 
Doesn't "fix" the problem but you can shut it off in gear then shift it to park until you figure it out.
 
Never heard of a Holley dual plane intake for the 440...

Something in the combustion chamber is too hot, enough to provide ign to the mixture after the key is turned off.

The cam is sizable for a 440 & will want at least 30* of timing at idle.
What will this do? Engine will run cooler; idle smoother; & will also allow a lower idle rpm. Best way to do this is with an adj vac adv unit connected to manifold vacuum. In the 70s, with all the pollution crap, engines ran hot....sometimes too hot. The fix to reduce temps was to switch from the useless ported VA to MVA....
Idle/ign timing is probably the most misunderstood topic on this forum & others...

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The ultimate cause is likely not enough ignition timing. With your timing light, pull in about 18 degrees initial timing at idle and then drop the idle speed at the carburetor to about 750-800 RPM and see if that solves the engine run on.
 
Lots of static compression and a smallish cam for that on pump gas may be in for some fun. Big RPM drop in gear s lots of time not enough timing.

Don't drive it if you dial in more initial timing as rusty suggest. Solve the shut off issue, then limit timing so your total number isn't out of bounds.
 
You may need to go to a step colder plug, once you have optimum idle timing & carb idle setting.

Your compression is fairly high, if the plug is too hot the ground strap can glow red hot. Acts like a glow plug in a Diesel engine.
 
Thank you to everyone foe the suggestions.

@Bewy my bad, yes the manifold is a single plane. Thank you for linking the articles and high lighting the text for me to read. Any idea which magazine that one was from?

@RustyRatRod

Thank you, i will try that.

@crackedback

Thank you, i will try that.

does anyone have suggestions on a spark plug that they have used and like for something like this?
 
My 440's love NGK plugs. Initial timing is found at idle with the minimum timing to obtain max vacuum. Then you MUST limit the added mechanical vacuum to not exceed 34 to 36 total. Vacuum advance needs to be reduced in most cases and run to manifold vacuum, so it falls away when the throttle is opened. to reduce tendency to detonate at higher open throttle settings where manifold vacuum approaches 0.

It's a balancing act, especially cruising on the freeway at high manifold vacuum with high gears and/or overdrive. I found that out the hard way, and never heard detonation.

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69,
Those articles were from different magazines/sources.
 
Thank you to everyone foe the suggestions.

@Bewy my bad, yes the manifold is a single plane. Thank you for linking the articles and high lighting the text for me to read. Any idea which magazine that one was from?

@RustyRatRod

Thank you, i will try that.

@crackedback

Thank you, i will try that.

does anyone have suggestions on a spark plug that they have used and like for something like this?


At 10.7:1 if that’s actually what it is and not a guess or just using an online calculator without taking actual measurements you need a Champion RC12YC.

Don’t buy the bullshit the NGK is mandatory. Before I tune anything I get Champion plugs in it.

When I’m done if the guy MUST have them I make sure the plug he wants to use matches the tune up. Plugs do not read the same. It’s far easier to read a Champion than an NGK and the Autolite is the most difficult to read.

RRR is correct. You do NOT need or want 30 initial. Thats just wrong for that compression, cam timing and displacement.

Then follow Crackedback’s advice and don’t drive it even if it likes the 18 initial. If you don’t correct the curve adding that much initial you’ll have too much total.
 
I believe Deey is meaning 30* including vacuum advance . But I would still be hesitant to do that. Besides unless the OP know how to curve a distributor he will have way to much total when done .
 
I believe Deey is meaning 30* including vacuum advance . But I would still be hesitant to do that. Besides unless the OP know how to curve a distributor he will have way to much total when done .


Check again.He said 30 at idle. It doesn’t need it. The only way to do it is hook up the vacuum advance to manifold vacuum.

It’s poor engine building that requires that kind of idle timing.

Fortunately for the OP his engine was built better than that.
 
Check again.He said 30 at idle. It doesn’t need it. The only way to do it is hook up the vacuum advance to manifold vacuum.

It’s poor engine building that requires that kind of idle timing.

Fortunately for the OP his engine was built better than that.
I understand and agree with you that it doesn’t need that much timing . But I would run manifold vacuum to keep my primary throttle plate transfer slot correct .
Speaking of which they may be open a bit too far thus the run on .
 
I understand and agree with you that it doesn’t need that much timing . But I would run manifold vacuum to keep my primary throttle plate transfer slot correct .
Speaking of which they may be open a bit too far thus the run on .
Sometimes there can be a time and a place for manifold vacuum.
 
The posts in this thread show how completely IGNORANT Newbomb Turk is about ign timing. Follow his advice at your peril....
The links [ below ] are from different engine brands. While there are slight variations in the exact timing numbers, the concept/theory is the same.

img100.jpg


img032.jpg


img035.jpg


img286.jpg


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img333.jpg
 
The posts in this thread show how completely IGNORANT Newbomb Turk is about ign timing. Follow his advice at your peril....
The links [ below ] are from different engine brands. While there are slight variations in the exact timing numbers, the concept/theory is the same.

View attachment 1716375389

View attachment 1716375390

View attachment 1716375391

View attachment 1716375392

View attachment 1716375393

View attachment 1716375394

I apologize right now for the long, confusing post. I always say it takes more words to correct an error than it does the post the error. This is an example of that.

It is a long read but IMHO it’s worth it.



I love how the first paragraph says he has the FACTS and not opinion.

That right there makes it suspect. But you do love your confirmation bias. That’s a fact.

What IS the fact is that not all engines need all that timing at idle. In fact, most do not need it.

I’ll use the OP as an example.

If his compression ratio is what he says it is, and if his cam timing is what he says it is, then at the very most it will need is 20 degrees at idle. And I give that about a 10% chance.

More likely it will need to be in the 16-18 degree range. Any more than that will do nothing but jack up the timing curve.

Let’s break it down both ways and see what it looks like. I have to make some assumptions here because the manifold vacuum always crowd never explain it in detail. Here we go.

Assuming the above engine needs the 30 initial claimed, you must use manifold vacuum advance because you can’t have that much initial mechanically and get the curve correct later in the rpm range. But wait…why am I agreeing with Bewy? Because if the compression ratio is low for the cam timing you either need to raise the compression ratio (expensive and labor intensive) or you need to reduce the cam timing which is also expensive and labor intensive. Or if you are way wrong on your build you may need to do both. Double expensive and labor intensive.

The quick and dirty way to deal with what I’ll call compromised build is to hook up manifold vacuum advance and jack a ton of idle timing in it.

It’s the cheapest and least labor intensive way to help correct a bad build.

It has serious drawbacks backs. For one we are dealing with a mechanical system. It takes time for the vacuum to drop enough to keep from getting tip in rattle. I hate tip in rattle.

We are not talking about several seconds of slow movement. But it’s slow enough to cause issues. Think it through. Let’s say it takes .5 seconds to get the MVA off. How long does it take for tip in rattle? Much less than that.

You have the surface area of the diaphragm to activate the mechanism. The bigger the surface area the slower the response. Then you have the actuating arm which rotates the cam plate and you have the cam plate.

All that **** has mass. All of it is moving. And it takes time to move it.

With a ton of timing to reduce at a tip in cruise you get the rattle. What else does it affect?

Well, once you give the distributor full time vacuum it’s always on. If your idle is 1000 rpm and you need the 30 claimed above, and your vacuum can starts adding timing at 11 inches and you have 10 inches of vacuum you either need to adjust the can to pull timing at less vacuum OR you need to increase the mechanical initial to cover that up.

So let’s say to make all this **** work somewhat together we decide we need 20 mechanical initial and 10 from the can. We go to the distributor machine and make it all happen.

We put it in the car and it’s rattling its brains out. Why is that? It’s because with that much mechanical initial you can’t shorten the curve enough to take enough timing out by peak torque rpm with the vacuum cam and it rattles. Again, why is that?

It’s because almost all engines (and I argue that ALL engines like we are discussing) want a timing curve. And that curve is based (basically) on peak torque and peak power.

All engines want MORE timing at peak power and LESS timing at peak torque.

We have now made the timing curve with enough initial that even when the vacuum comes off it has too much timing and it rattles.

You can continue to go around and around trying to tune the rattle out of it by varying initial timing, trying to slow the curve down (which in turn when you get to full power/low vacuum affects the curve) or worse yet limiting the total advance, which in turn kills peak power.

If you use MVA rather than timed (ported) VA you can not change the point where the VA starts because you’ve already started it.

Does this sound confusing and circular? It should because it is both of those.

Of course if I’m wrong and the OP’s build is as screwed up as some think it is, then MVA will not cause a tip in rattle nor will it show a power loss on the dyno.

But Turk, you can’t tune and test for this on the dyno. You surely must know that.

I beg to differ. You can do it if you want to and you know how to do it. It’s not hard. It is time consuming.

What you will see in the power numbers on the dyno is the inability to get the timing curve correct for peak torque and peak power. You’ll kill power at one or the other. Sometimes both.

If you have to increase the mechanical initial because you don’t have enough idle timing with MVA then you screw the curve for the time when the MVA comes off. Too much initial relative to MVA means without MVA the curve will have too much timing too soon.

We can continue to try and clean it up but all that happens is you shift the crappy part of the curve to a different rpm.

And what about the claims of engines needing as much as 50 (FIFTY) degrees of idle timing? How in the world do you get a curve correct for the times when the MVA is off? You can’t.

Let’s look at the other end of the curve.

Chrysler small blocks generally need 35 total or less. If the quench is tight you might only need 30 total. The BB stuff with OEM heads might need as high as 40 total. If you have aftermarket heads you’ll be in the 30-35 total range.

Saying that and agreeing that it a fact (it is) then how in THE hell do you deal with 30 degrees of initial timing when the engine at full song only needs at the maximum 5 more degrees of timing at that point? Or if it needs ZERO added timing when the MVA comes off. You don’t.

You may be able to do it if a computer controls your timing but no way can you deal with that type of curve mechanically.

What if the claim is 50 at idle with a total timing need of 30??? Or 35?? Or even 40??? Again, it’s an inverted curve and getting that in shape mechanically is near impossible. I can’t say it’s impossible because someone somewhere wrote an article on how they did it, but of course there is no verifying testing to prove it.

Of course if the engine really needs all that initial and you don’t want to fix it the correct (hard) way then use MVA.

TL;DR it is very complicated to make MVA work if the engine doesn’t need it. Most don’t. The moral of the story is build the engine with the cam timing that fits your compression ratio and you won’t need crap like MVA at idle.
 
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@Newbomb Turk So basically the answer is we get fully programmable ignition systems?
There’s only so much you can do with stretching springs, advance weights & vacuum canisters.
 
I apologize right now for the long, confusing post. I always say it takes more words to correct an error than it does the post the error. This is an example of that.

It is a long read but IMHO it’s worth it.



I love how the first paragraph says he has the FACTS and not opinion.

That right there makes it suspect. But you do love your confirmation bias. That’s a fact.

What IS the fact is that not all engines need all that timing at idle. In fact, most do not need it.

I’ll use the OP as an example.

If his compression ratio is what he says it is, and if his cam timing is what he says it is, then at the very most it will need is 20 degrees at idle. And I give that about a 10% chance.

More likely it will need to be in the 16-18 degree range. Any more than that will do nothing but jack up the timing curve.

Let’s break it down both ways and see what it looks like. I have to make some assumptions here because the manifold vacuum always crowd never explain it in detail. Here we go.

Assuming the above engine needs the 30 initial claimed, you must use manifold vacuum advance because you can’t have that much initial mechanically and get the curve correct later in the rpm range. But wait…why am I agreeing with Bewy? Because if the compression ratio is low for the cam timing you either need to raise the compression ratio (expensive and labor intensive) or you need to reduce the cam timing which is also expensive and labor intensive. Or if you are way wrong on your build you may need to do both. Double expensive and labor intensive.

The quick and dirty way to deal with what I’ll call compromised build is to hook up manifold vacuum advance and jack a ton of idle timing in it.

It’s the cheapest and least labor intensive way to help correct a bad build.

It has serious drawbacks backs. For one we are dealing with a mechanical system. It takes time for the vacuum to drop enough to keep from getting tip in rattle. I hate tip in rattle.

We are not talking about several seconds of slow movement. But it’s slow enough to cause issues. Think it through. Let’s say it takes .5 seconds to get the MVA off. How long does it take for tip in rattle? Much less than that.

You have the surface area of the diaphragm to activate the mechanism. The bigger the surface area the slower the response. Then you have the actuating arm which rotates the cam plate and you have the cam plate.

All that **** has mass. All of it is moving. And it takes time to move it.

With a ton of timing to reduce at a tip in cruise you get the rattle. What else does it affect?

Well, once you give the distributor full time vacuum it’s always on. If your idle is 1000 rpm and you need the 30 claimed above, and your vacuum can starts adding timing at 11 inches and you have 10 inches of vacuum you either need to adjust the can to pull timing at less vacuum OR you need to increase the mechanical initial to cover that up.

So let’s say to make all this **** work somewhat together we decide we need 20 mechanical initial and 10 from the can. We go to the distributor machine and make it all happen.

We put it in the car and it’s rattling its brains out. Why is that? It’s because with that much mechanical initial you can’t shorten the curve enough to take enough timing out by peak torque rpm with the vacuum cam and it rattles. Again, why is that?

It’s because almost all engines (and I argue that ALL engines like we are discussing) want a timing curve. And that curve is based (basically) on peak torque and peak power.

All engines want MORE timing at peak power and LESS timing at peak torque.

We have now made the timing curve with enough initial that even when the vacuum comes off it has too much timing and it rattles.

You can continue to go around and around trying to tune the rattle out of it by varying initial timing, trying to slow the curve down (which in turn when you get to full power/low vacuum affects the curve) or worse yet limiting the total advance, which in turn kills peak power.

If you use MVA rather than timed (ported) VA you can not change the point where the VA starts because you’ve already started it.

Does this sound confusing and circular? It should because it is both of those.

Of course if I’m wrong and the OP’s build is as screwed up as some think it is, then MVA will not cause a tip in rattle nor will it show a power loss on the dyno.

But Turk, you can’t tune and test for this on the dyno. You surely must know that.

I beg to differ. You can do it if you want to and you know how to do it. It’s not hard. It is time consuming.

What you will see in the power numbers on the dyno is the inability to get the timing curve correct for peak torque and peak power. You’ll kill power at one or the other. Sometimes both.

If you have to increase the mechanical initial because you don’t have enough idle timing with MVA then you screw the curve for the time when the MVA comes off. Too much initial relative to MVA means without MVA the curve will have too much timing too soon.

We can continue to try and clean it up but all that happens is you shift the crappy part of the curve to a different rpm.

And what about the claims of engines needing as much as 50 (FIFTY) degrees of idle timing? How in the world do you get a curve correct for the times when the MVA is off? You can’t.

Let’s look at the other end of the curve.

Chrysler small blocks generally need 35 total or less. If the quench is tight you might only need 30 total. The BB stuff with OEM heads might need as high as 40 total. If you have aftermarket heads you’ll be in the 30-35 total range.

Saying that and agreeing that it a fact (it is) then how in THE hell do you deal with 30 degrees of initial timing when the engine at full song only needs at the maximum 5 more degrees of timing at that point? Or if it needs ZERO added timing when the MVA comes off. You don’t.

You may be able to do it if a computer controls your timing but no way can you deal with that type of curve mechanically.

What if the claim is 50 at idle with a total timing need of 30??? Or 35?? Or even 40??? Again, it’s an inverted curve and getting that in shape mechanically is near impossible. I can’t say it’s impossible because someone somewhere wrote an article on how they did it, but of course there is no verifying testing to prove it.

Of course if the engine really needs all that initial and you don’t want to fix it the correct (hard) way then use MVA.

TL;DR it is very complicated to make MVA work if the engine doesn’t need it. Most don’t. The moral of the story is build the engine with the cam timing that fits your compression ratio and you won’t need crap like MVA at idle.
I agree with some of what you say but not all. It seems like one of the reasons you use as an argument against MVA is that it messes up the curve elsewhere in the rpm range. The examples you use to support this are in my opinion tuning it backwards. You're adding the MVA first. Why not tune the curve the way you think is the best mechanical then add and tune the MVA last if the motor wants it.

My opinion is that MVA would be better named as "vacuum advance at idle". It's less confusing. Ported vacuum is the same thing as MVA minus the vacuum at idle. Why even have vacuum advance? Why not just have mechanical advance? (By the way I think mechanical or centrifugal advance should be renamed rpm based timing or rpm timing for short.) To start with you don't need mechanical or vac advance. You can lock your distributor down and set it to a best compromised number and call it good. In some applications this is useful. Because motors will run better with less or more timing at different rpms adding mechanical advance is helpful. Engines also want different timing under different loads. Using vacuum as an indicator of load on the engine allows us to change the timing curve based on load. And we have two options for vacuum, manifold or ported. Of course now we have electronic timing control. Some would argue that is the best.

If you add MVA (again if the motor wants it) last then the "right mechanical curve" will still be the "right mechanical curve above idle." So if a timing problem occurs after adding the MVA it is a problem with vacuum advance curve. Which can be tuned in most cases for starting point and total vac advance added with different, modified or adjustable vacuum advance mechanisms.

I don't completely agree that if you can benefit from MVA or vac advance at idle that your motor is built wrong. How you build your motor depends on a lot of things including your application. There is vast range of possibilities for different combinations and it is likely that some will benefit from MVA.

The problem you expose with the time delay of the drop out of the vac advance may or may not be a problem. I could be more of a problem with a sticky mechanism or stiff diaphram. But again in my opinion it's not certain to be a problem in every case so why not try it first. Also if it is a problem it is likely to also be a problem for ported vacuum.

Probably the biggest problem again IMHO is having the time, patience and understanding to develop the best timing curve for your application. It can be a real time suck and you will be tempted to say at some point "good enough " or "I give up" or "I need someone else to do this"all legitimate responses. But if your committed and can develop the proper mechanical curve you can probably handle the vac curve. This process may involve comprises.

All that said I have the timing locked on one of my street cars and on my racecar. It's Fast ignition, doesn't retard with rpm like others and has a built in start retard. Is it ideal for the street car? Maybe not but I'm satisfied. For now.
 
The posts in this thread show how completely IGNORANT Newbomb Turk is about ign timing. Follow his advice at your peril....
The links [ below ] are from different engine brands. While there are slight variations in the exact timing numbers, the concept/theory is the same.

View attachment 1716375389

View attachment 1716375390

View attachment 1716375391

View attachment 1716375392

View attachment 1716375393

View attachment 1716375394
Sometimes MVA is helpful and workable and sometimes it can cause unintended consequences. As usual it is combination specific. Not every combination will want it and even if it does you may have to compromise how much you give it. What is good at idle might be too much at cruise.
While it could be as simple as plugging the vacuum can to MVA often times it requires more steps and for some people it's too much. Not saying that is a good reason not a good reason to do it.
 
@Newbomb Turk So basically the answer is we get fully programmable ignition systems?
There’s only so much you can do with stretching springs, advance weights & vacuum canisters.

At some point…yes.

I may be at that point with my junk. It looks like it will be a bit over 12:1 compression. Like 12 and a quarter. I won’t know until I do the down fill and the math but it won’t be less than 12:1.

I absolutely want to run vacuum advance. I’m also going to run manifold vacuum to the fuel bypass regulator.

That will reduce fuel pressure as manifold vacuum goes up. It has a similar effect like VA by reducing fuel pressure at idle and cruise and by doing that it leans the carb out.

My initial thinking is I’m going to need something like 20-22 initial, maybe 26 at peak torque (that should be about 5200ish) and 32-33ish at 6700ish.

If I’m even close on my numbers it’s going to be hard to get that curve.

I may have to wind my own springs (PITA), see if I can buy a spring with enough rate to control the weights or/and modify the weights.

If I can’t get what I need then I’ll have to buy a crank trigger and a Programmable Digital 7 from MSD.

I really do NOT want to do that.

If by some miracle I get the curve acceptable then I need to start working on the VA.

Or, I could shove an ice pick in my ear. That may be easier on me than getting the curve correct.
 
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